Inconel 718 vs Hastelloy C-276: Strength or Corrosion?

By Shanghai Hangbo Alloy Group Co., Ltd. - China Supplier | ISO 9001:2015 | Est. 2012

Contact: sales@hangboalloy.com | hangbo@nickel-alloy.com | WhatsApp (Lisa): +86 13611656360

Quick Answer: Inconel 718 or Hastelloy C-276?

Choose Inconel 718 when the component must carry high load to about 650 °C and the environment is only mildly corrosive; choose Hastelloy C-276 when aggressive chlorides, mixed or reducing acids and wet chlorine dominate and strength is secondary. Where both high strength and severe corrosion are required, neither alloy is sufficient.

Key Takeaways

• This is a comparison between two alloying strategies, not two grades of one family. Inconel 718 is a nickel-iron-chromium alloy hardened by a gamma-double-prime precipitate; Hastelloy C-276 is a nickel-molybdenum-chromium alloy that is never hardened at all, because it has no precipitation-hardening response.
• 718 wins on strength and C-276 wins on corrosion, and the gap runs in both directions. Aged 718 is specified at a minimum of 1034 MPa (150 ksi) yield strength under AMS 5662; annealed C-276 is a roughly 355 MPa class material, yet it resists hydrochloric acid, wet chlorine and chloride pitting that 718 cannot survive.
• Neither alloy substitutes for the other, and there are duties where neither is correct. Where high strength and severe reducing-acid corrosion are needed together, the usual answers are clad or lined construction, a bolted hybrid design, or an intermediate age-hardenable grade such as Inconel 725 (UNS N07725).
• Both alloys have a weakness in the 650–900 °C band, for entirely different reasons. 718 overages as gamma double prime transforms to delta phase above roughly 650 °C, while C-276 precipitates carbides and intermetallic phases that reduce corrosion resistance and ductility.
• The welding requirements are close to opposite. 718 is generally welded in the solution-treated condition and then solution treated and aged; C-276 needs no post-weld heat treatment at all, but needs tight control of heat input to avoid secondary-phase precipitation.
• Price follows alloying content, not strength. C-276 carries 15–17 % molybdenum plus 3.0–4.5 % tungsten and is the more expensive of the two per kilogram in every product form, so the correct comparison is total installed cost rather than cost per kilogram.

What Is the Difference Between Inconel 718 and Hastelloy C-276?

Inconel 718 is a precipitation-hardening nickel-iron-chromium alloy that is strengthened by a two-step ageing treatment to a specified minimum yield strength of about 1030 MPa, while Hastelloy C-276 is a solid-solution nickel-molybdenum-chromium alloy that is never aged and is selected for resistance to chlorides, mixed acids and wet chlorine. The two are not competing grades of a single family: 718 is a high-strength structural alloy with moderate corrosion resistance, and C-276 is a corrosion alloy with only moderate strength. The selection therefore begins with which of those two requirements governs the design, and only after that with price.

The reason the two alloys behave so differently is that they use nickel for different purposes. In Alloy 718, nickel at 50–55 % acts as the matrix for a carefully balanced set of additions — niobium plus tantalum at 4.75–5.50 %, titanium at 0.65–1.15 % and aluminium at 0.20–0.80 % — that can be put into solution at high temperature and then precipitated as a coherent gamma-double-prime phase during ageing. That precipitate strains the lattice and blocks dislocation movement, which is why the yield strength roughly doubles between the solution-treated and the aged condition, and why the alloy is the workhorse of turbine discs, compressor casings, high-temperature fasteners and downhole hardware. Its chromium content of 17–21 % and molybdenum content of 2.80–3.30 % give it useful corrosion resistance, but they are sized for oxidation and moderate chemical duty rather than for the aggressive media that nickel alloys are normally bought for.

In Hastelloy C-276 the alloying additions do a different job. Nickel is the solvent; chromium at 14.5–16.5 % provides the passive film; molybdenum at 15.0–17.0 % and tungsten at 3.0–4.5 % provide resistance to reducing acids, to pitting and to crevice attack; and carbon is held to 0.010 % maximum so that carbide precipitation is suppressed after welding. There is no precipitate to form and therefore no ageing cycle, no solution-treat-and-age sequence, and no strength gain from heat treatment. The alloy is supplied solution annealed and quenched, and every subsequent thermal operation is judged by one criterion only: whether it preserved or destroyed the corrosion resistance.

This difference has a commercial consequence that buyers notice early. Because 718 is specified on strength as well as identity, its purchase order is an aerospace-style document naming a melting practice, a heat treatment cycle and a hardness limit, while a C-276 order is a chemical-process document naming a corrosion environment and an inspection document. Mixing the two styles of specification is one of the most common causes of rejected material in this material family, and it is avoided by naming the UNS number, the product standard and the condition on every order.

The Inconel alloy range and the Hastelloy alloy range are stocked separately for exactly this reason, and our related technical guides published under nickel alloy news and comparisons cover the neighbouring selection questions.

Composition: One Alloy Ages, the Other Cannot

The composition table below is the root of every difference discussed in this article. Reading it vertically shows why 718 responds to ageing and why C-276 does not; reading it horizontally shows how far apart the two alloys sit in chromium, molybdenum and carbon.

Element	Inconel 718, UNS N07718 (wt %)	Hastelloy C-276, UNS N10276 (wt %)	Product standard (example form)
Ni	50.0–55.0	balance	ASTM B637 / ASTM B575
Cr	17.0–21.0	14.5–16.5	ASTM B637 / ASTM B575
Mo	2.80–3.30	15.0–17.0	ASTM B637 / ASTM B575
W	—	3.0–4.5	ASTM B575
Nb + Ta	4.75–5.50	—	ASTM B637
Ti	0.65–1.15	—	ASTM B637
Al	0.20–0.80	—	ASTM B637
Co	1.00 max	2.50 max	ASTM B637 / ASTM B575
Fe	balance	4.0–7.0	ASTM B637 / ASTM B575
Mn	0.35 max	1.00 max	ASTM B637 / ASTM B575
Si	0.35 max	0.08 max	ASTM B637 / ASTM B575
C	0.08 max	0.010 max	ASTM B637 / ASTM B575
P	0.015 max	0.040 max	ASTM B637 / ASTM B575
S	0.015 max	0.030 max	ASTM B637 / ASTM B575
Cu	0.30 max	—	ASTM B637
V	—	0.35 max	ASTM B575
B	0.006 max	—	ASTM B637

Table note: Ranges are the standard minimum and maximum limits stated in the ASTM product standards named in the final column (latest editions), which differ slightly between plate, bar, tube and forging. Values quoted as a single maximum are standard minima and maxima of the same type. The controlling limits are always those of the standard and product form named on the purchase order. Chemistry is verified by X-ray fluorescence or optical emission spectrometry, with ASTM E1476 providing the general guide to metals identification and ASTM E572 the X-ray spectrometric method for nickel alloys.

Two compositional facts decide the engineering behaviour of each alloy. The first is that 718 has enough niobium, titanium and aluminium in the correct ratio to form gamma double prime, and the carbon is deliberately held at 0.08 % maximum so that carbon does not compete for the niobium that the strengthening precipitate needs. The second is that C-276 has 4.5 to 6 times the molybdenum of 718 together with tungsten, and a carbon limit one eighth as high. That combination is what produces roughly 70–76 PREN in C-276 against roughly 27–31 in 718, and it is also why C-276 is a solid-solution alloy by design: any precipitate that formed in service would remove molybdenum and chromium from solution and reduce the corrosion resistance the alloy was bought for.

Because both alloys are traded internationally, the same material appears under several designation systems, and a specification written in one system is frequently translated into another by a buyer who does not hold the original. The cross-reference table below sets out the equivalences that matter, including the Chinese, Japanese, German and Russian designations.

Family	UNS	Common trade name	China (GB)	Japan (JIS)	Germany (DIN / W.Nr)	Russia (GOST)
Age-hardenable Ni-Fe-Cr	N07718	Inconel 718, Alloy 718	GH4169 (GB/T 14992)	NCF 718 (JIS G 4901)	2.4668 (DIN 17744)	GOST 5632 (718-type grade)
Solid-solution Ni-Mo-Cr	N10276	Hastelloy C-276, Alloy C-276	NS334 (GB/T 15007)	NCF C276 (JIS G 4902)	2.4819 (DIN 17744)	GOST 5632, ХН65МВ family
Related refractory Ni-Cr-W-Mo	—	GH3128 (not a C-276 equivalent)	GH3128	—	—	—

Table note: Cross-references are indicative equivalents for wrought product and are not interchangeable clause by clause; the designations of the GH and NS series are defined in the GB standards named, the NCF series in the JIS superalloy standards, and the Werkstoff numbers in the DIN wrought nickel alloy standard. Where a project specifies a Chinese, Japanese, German or Russian grade, the composition and property requirements of that system govern and must be stated on the order in parallel with the UNS number rather than instead of it. The Russian ХН65МВ grade is quoted as a family reference to GOST 5632 and its exact designation for the C-276 composition should be confirmed against the latest edition of that standard (待核 for the specific grade clause). Inspection documents for all of these systems are normally requested to EN 10204 as 3.1 or 3.2.

Mechanical Properties: How Much Strength Does 718 Add?

Inconel 718 in the solution-treated and aged condition is roughly two and a half to three times as strong as annealed Hastelloy C-276 at room temperature, and the difference is a specified minimum rather than a typical scatter band. C-276 has no corresponding minimum that is comparable in magnitude, because it is not a structural alloy in the same sense.

Alloy and condition	Test temperature	Tensile strength	0.2 % yield strength	Elongation	Hardness	Standard basis
Inconel 718, solution treated + aged	20 °C	1240 MPa min (standard minimum)	1034 MPa min (standard minimum)	12 % min (standard minimum)	331 HB min / 36 HRC min (standard minimum)	AMS 5662 / AMS 5663
Inconel 718, solution treated + aged, bar and forging	20 °C	1240 MPa min (standard minimum)	1030 MPa min (standard minimum)	12 % min (standard minimum)	—	ASTM B637 / ASME SB637
Inconel 718, solution treated only (as delivered for subsequent ageing)	20 °C	~900–1100 MPa (typical)	~550–760 MPa (typical)	~20–35 % (typical)	~200–280 HV (typical)	typical, not a standard minimum
Inconel 718, aged	650 °C	~1000–1100 MPa (typical)	~860–910 MPa (typical)	~15–25 % (typical)	—	typical, not a standard minimum
Inconel 718, aged	700 °C	~900–1000 MPa (typical)	~780–830 MPa (typical)	~15–25 % (typical)	—	typical, not a standard minimum
Inconel 718, cold-drawn bar and fastener stock	20 °C	~1300–1500 MPa (typical)	~1100–1300 MPa (typical)	~12–20 % (typical)	~38–44 HRC (typical)	in-house, not a standard requirement
Hastelloy C-276, solution annealed	20 °C	~790 MPa (typical)	~355 MPa (typical)	~40–60 % (typical)	~200 HV / ~92 HRB (typical)	ASTM B575 / ASTM B574 (typical of annealed product)
Hastelloy C-276, solution annealed	400 °C	~630–680 MPa (typical)	~270–310 MPa (typical)	~45–60 % (typical)	—	typical, not a standard minimum
Hastelloy C-276, solution annealed	650 °C	~520–570 MPa (typical)	~230–260 MPa (typical)	~45–60 % (typical)	—	typical, not a standard minimum
Hastelloy C-276, cold-worked bar and wire	20 °C	~1000–1250 MPa (typical)	~800–1100 MPa (typical)	~5–20 % (typical)	~30–40 HRC (typical)	in-house, not a standard requirement

Table note: The Inconel 718 room-temperature figures marked standard minimum are the acceptance values specified for bar, forgings and rings in AMS 5662 and AMS 5663, with the ASTM B637 values shown separately because the two documents set slightly different yield minima and apply to different product forms; the minimum on the order governs and the figures are not interchangeable between forms or sizes. The Hastelloy C-276 room-temperature figures are typical of annealed product; the acceptance minima for a specific form and size are those stated in the ASTM product standard named on the order (confirm the governing figure for the form, size and edition ordered — 待核 for the exact value). All elevated-temperature figures are typical published values and are explicitly not standard minima, because the room-temperature requirements of these product standards are not extended to high temperature; elevated-temperature design data should be taken from the applicable ASME code case or from a qualified test programme. Tensile testing is performed to ASTM E8/E8M at room temperature and ASTM E21 at elevated temperature, hardness testing to ASTM E10 or E18, and grain size determination to ASTM E112.

The engineering reading of the table is direct. If the component is defined by stress — a turbine disc, a compressor blade root, a bolted flange in a high-pressure line, a downhole hanger, a high-temperature spring — the only candidate in this pair is 718, and the specification should quote the AMS 5662 or ASTM B637 minimum with the product form and size so that the supplier cannot deliver a lower-strength condition. If the component is defined by corrosion — a reactor, a column internals package, a duct, a heat exchanger in chlorinated seawater — then C-276 is the candidate and its roughly 355 MPa annealed yield strength is usually adequate, because chemical process equipment is designed on stiffness, corrosion allowance and code allowable stress rather than on the pursuit of yield strength.

Two secondary observations are worth recording. C-276 can be cold worked to roughly 800–1100 MPa yield, and that is done for fasteners and wire, but the strength is bought at a large cost in elongation, the cold work is destroyed by welding, and the corrosion resistance in the most aggressive media is not improved by it. Similarly, 718 can be cold drawn to 1100–1300 MPa yield for fastener stock, but the material is then in a state where strain-age cracking during welding becomes a real risk, which is the subject of the fabrication section below.

Heat Treatment: Dual-Age 718 Versus Solution-Annealed C-276

Inconel 718 must be solution treated and then given the AMS 5662 two-step ageing treatment — 720 °C for 8 hours, controlled cooling to 620 °C, then a further 8 hours — before it achieves the properties it is bought for, while Hastelloy C-276 is supplied in the solution-annealed and rapidly quenched condition and no subsequent ageing treatment is applied or useful. Reversing these expectations, or applying an ageing cycle to C-276, wastes a furnace cycle and produces no property change.

Alloy	Operation	Temperature and cycle	Purpose	Effect on properties	Standard basis
Inconel 718	Solution treatment	~954–982 °C hold, then rapid quench (some product forms and aerospace cycles use 941–1010 °C)	dissolve gamma double prime and delta phase, homogenise, condition for ageing	soft, formable, machinable condition	AMS 5662 / ASTM B637
Inconel 718	First ageing step	720 °C ± 8 °C for 8 h, then controlled cooling at about 50 °C/h to the second step	nucleate gamma double prime	major strength increase	AMS 5662 / AMS 5663
Inconel 718	Second ageing step	620 °C ± 8 °C for 8 h, then air cool	complete gamma double prime precipitation	peak aged strength with retained ductility	AMS 5662 / AMS 5663
Inconel 718	Post-weld heat treatment	solution treatment + dual ageing as above, after welding in the solution-treated condition	restore HAZ properties, avoid strain-age cracking	joint properties close to parent	customer specification / ASME Section IX (procedure qualification)
Inconel 718	Stress relief of finished parts	not applied above the second ageing temperature without re-ageing	—	ageing cycle doubles as stress relief	mill practice
Hastelloy C-276	Solution anneal	~1040–1120 °C, then rapid water quench	dissolve carbides and intermetallic phases, restore corrosion resistance	softest, most corrosion-resistant condition	ASTM B575 / B574 / B622
Hastelloy C-276	Stress relief	not generally required; partial stress relief below ~900 °C can reduce corrosion resistance and should be avoided	—	—	mill practice
Hastelloy C-276	Ageing	not applicable — the alloy has no precipitation-hardening response	—	no hardening from heat treatment	—
Hastelloy C-276	Post-weld heat treatment	not required; where specified, only a full solution anneal plus quench is acceptable	restore weld and HAZ corrosion resistance	corrosion resistance restored	ASTM B619 / B626 and mill practice

Table note: The Inconel 718 cycles shown are the customary shop values of the two-step ageing treatment required by AMS 5662 and AMS 5663 for bar, forgings and rings; the mandatory temperatures, tolerances, cooling rates and furnace instrumentation requirements are those of the controlling specification on the order, and where an aerospace or customer specification applies the pyrometry is normally performed to AMS 2750. The C-276 solution-anneal range is that of the ASTM product standards; the exact soak time and cooling rate are set by the supplier's qualified practice. Neither the 718 ageing temperature nor the C-276 anneal temperature should be inferred from a generic "heat treat per ASTM" clause on a drawing, because the two alloys respond to opposite instructions and the clause does not distinguish them.

Three points belong in a purchase order for these grades. First, state the delivered condition without ambiguity, because 718 is routinely traded both solution treated and solution-treated-and-aged, and the two conditions differ by a factor of roughly 1.5 in yield strength. Second, if 718 will be welded, state whether it is to be welded in the aged or the solution-treated condition, because the fabrication sequence determines whether post-weld solution treatment is required and whether strain-age cracking is a risk. Third, if C-276 will be hot formed or stress relieved at any stage, verify that the final thermal operation restores the solution-annealed condition, because an intermediate anneal below the solution temperature is exactly the treatment that produces the secondary phases the alloy is bought to avoid.

Corrosion Resistance: Mixed Acids, Chlorides, Pitting and PREN

Hastelloy C-276 resists substantially more chemical environments than Inconel 718, and the gap is widest exactly where the environments are worst: reducing acids, hydrochloric acid above dilute concentrations, wet chlorine, oxidising chloride mixtures and chlorinated seawater containing crevices. Inconel 718 is a moderate-corrosion alloy with excellent resistance to oxidation and to mildly oxidising media, and it should not be specified as a chemical-resistant material merely because it is described as a nickel alloy.

Environment	Inconel 718	Hastelloy C-276	Preferred choice and why
Hydrochloric acid, 5–20 %, 20–60 °C	limited	excellent	C-276 — Mo plus W stabilise the alloy in a reducing acid
Hydrochloric acid, concentrated, hot	not suitable	very good	C-276
Sulphuric acid, dilute, aerated	good	excellent	either; C-276 for higher temperature or concentration
Sulphuric acid, 50 %, 60 °C, reducing	moderate	excellent	C-276
Mixed hydrochloric + oxidising species (FeCl3, Cl2)	not suitable	excellent	C-276 — the classic application for this alloy
Wet chlorine gas and hypochlorite	limited	very good	C-276
Chlorinated seawater with crevices or deposits	moderate (pitting and crevice risk)	very good	C-276, or titanium for high velocity
Seawater, ambient, no crevice, low velocity	good	very good	either; commercial decision
Phosphoric acid, contaminated with chlorides and fluorides	moderate	excellent	C-276
Nitric acid, oxidising	good	good	either; C-276 for chloride contamination
Caustic soda, concentrated, hot	good	good	either; Monel 400 or Nickel 200 for the highest caustic duty
Chloride stress-corrosion cracking above 60 °C	resistant	resistant	both are high-nickel alloys and are immune to the SCC that attacks 304 and 316
Sour service (H2S with chlorides), to ~200 °C	very good (to 40 HRC max)	good	718 is the conventional high-strength choice, subject to NACE MR0175
Oxidising high-temperature gas, 800–1000 °C	good	limited	718 for oxidation plus strength; C-276 loses strength and precipitates phases
PREN (typical, calculated)	~27–31	~70–76	C-276 by a wide margin

Table note: The ratings are relative performance for the two alloy families and are not a substitute for service-specific data; the governing references are the corrosion data published with the applicable product standard and the process licensor's material selection diagrams. Where a specific medium, concentration, aeration condition and temperature combination governs the design, the correct approach is to obtain corrosion rates for that combination, and where the data are unavailable, to run an immersion test in the actual process liquor against an agreed acceptance criterion. PREN is calculated as Cr + 3.3 (Mo + 0.5 W) and is a comparative indicator only; it is a typical calculated value and is not a standard requirement, and the standard does not publish a PREN acceptance limit for either alloy. Sour-service limits follow NACE MR0175 / ISO 15156 and are expressed as a hardness cap rather than as a corrosion limit; our guide to sour service to NACE MR0175 covers how the hardness limit is applied. Pitting and crevice resistance are normally compared by ASTM G48 and intergranular corrosion susceptibility by ASTM G28, and our buyers' guide to corrosion testing to ASTM G48 and G28 explains how those test results should be read.

The mechanism behind the table explains why the ratings do not vary with strength. C-276 protects itself with a molybdenum- and tungsten-rich surface that resists reducing acids, and it supplements that with a chromium-rich passive film for oxidising conditions, which is why it handles mixed acid streams that defeat single-mechanism alloys. Inconel 718 protects itself almost entirely with a chromium oxide film, and it is a leaner film than the one on Inconel 625 or C-276 because the chromium level is lower and the molybdenum level is modest. In a fully aerated, mildly oxidising environment that leaner film is perfectly sufficient and 718 performs well; in a reducing acid or in an oxidising chloride mixture that concentrates in a crevice, the film either cannot form or is destroyed faster than it repairs, and attack proceeds.

Two practical consequences follow. First, the fact that 718 is used successfully in sour gas wellheads, in high-pressure downhole tubing and in aerospace engines does not make it a chemical-process alloy, and quoting it for a hydrochloric acid duty because it has a higher strength will normally produce rapid failure. Second, C-276 is frequently replaced by cheaper grades — 625, 22, C-4 or 686 — when the duty is less severe than wet chlorine or concentrated hydrochloric acid, and the same test data that would disqualify 718 will usually show whether the substitution is safe. Our comparison of Hastelloy C-276 with C-4 and C-22 sets out where the molybdenum and tungsten content can be reduced without unacceptable risk.

What Is the Maximum Service Temperature for Each Alloy?

Inconel 718 is the higher-temperature alloy of the two for load-bearing service: it holds useful strength to about 650 °C in continuous operation and is used to roughly 700 °C for shorter periods, whereas Hastelloy C-276 is a corrosion alloy whose oxidation resistance extends to about 1040 °C but whose strength is low and whose microstructure degrades if it is held in the 650–1000 °C band. The two alloys therefore have temperature limits that are set by different mechanisms and cannot be compared on a single scale.

For 718 the limit is metallurgical. The gamma-double-prime precipitate that provides the strength is metastable, and above roughly 650 °C it transforms progressively into the stable delta phase, which is coarser, less coherent and far less effective at blocking dislocations. The consequence is overageing: an 718 component held at 700 °C for a long period will lose a substantial part of its yield strength, and the loss is not recoverable by re-ageing without a full solution treatment. Below the transformation temperature the alloy is stable, which is why gas turbine and aerospace practice keeps continuous 718 duty at or below about 650 °C and reserves the 650–700 °C band for short excursions. Oxidation itself is not the limitation at that temperature, and 718 resists scaling well to around 800–900 °C if no load has to be carried.

For C-276 the limit is different in kind. The alloy resists oxidation to about 1040 °C (approximately 1900 °F) on an intermittent basis and has good resistance to scaling in that range, but it is not a structural high-temperature alloy: its room-temperature yield strength of roughly 355 MPa annealed falls to about 230–260 MPa at 650 °C and continues to fall above that. Worse, when C-276 is held in the 650–1000 °C range, carbides and intermetallic phases precipitate at the grain boundaries, removing molybdenum and chromium from solid solution and reducing both ductility and corrosion resistance. A C-276 vessel that has been exposed in that band and then returned to an aggressive chemical duty will corrode differently from one that has not, which is why fabrication procedures for this alloy specify low heat input, controlled interpass temperature and, where any significant thermal exposure has occurred, a final solution anneal.

The overlap between the two limits is the practical trap. Between roughly 650 °C and 900 °C both alloys are on the wrong side of their own limitation at the same time: 718 is overageing and C-276 is precipitating secondary phases. A duty that requires both high strength and chemical resistance in that band cannot be met by either alloy, and the realistic solutions are a different grade — Inconel 625 or 617 where oxidation and strength are needed, Hastelloy C-22 or C-2000 where the corrosion is the issue — or a change in the process temperature. Our high-temperature alloy comparison covers the grades above 650 °C in more detail.

Welding and Fabrication: Which Alloy Is Easier to Join?

Both alloys are weldable, but the procedures, the fillers and the failure modes are entirely different. Inconel 718 is the more demanding of the two on heat treatment sequencing, because the joint must be solution treated and aged after welding if it is to recover parent-metal properties; Hastelloy C-276 is the more demanding on heat input, because excessive welding energy produces the secondary phases that destroy its corrosion resistance even though no post-weld heat treatment is needed.

Inconel 718 in the solution-treated condition welds cleanly by gas tungsten arc, gas metal arc, plasma and electron beam processes, and the alloy is notable among the precipitation-hardening superalloys for its tolerance of welding — it is markedly less crack-sensitive than Waspaloy or Rene 41. The difficulty lies in the sequence. Welding 718 that is already aged, or performing a post-weld stress relief in the 650–870 °C range before the full solution treatment, places the material in the temperature band where relaxation of residual stress and precipitation of the strengthening phase occur together, and the result can be strain-age cracking in the heat-affected zone. Standard practice is therefore to weld in the solution-treated condition, then solution treat and age the assembly with the dual cycle of AMS 5662. Filler metal is normally ERNiFeCr-2 wire to AWS A5.14, with covered electrodes in the ENiCrFe class to AWS A5.11, and the procedure should be qualified to ASME Section IX where a code applies.

Hastelloy C-276 welds by the same arc processes, with ERNiCrMo-4 wire to AWS A5.14 and ENiCrMo-4 electrodes to AWS A5.11 as the matching consumables. The alloy has a lower thermal expansion and higher hot strength than austenitic stainless steel and is not considered a hot-cracking problem, but the weld and heat-affected zone are solution-annealed by the welding thermal cycle only if the cooling is fast enough, and slow cooling or excessive heat input allows carbide and intermetallic precipitation that shows up as reduced corrosion resistance in the weld zone rather than as reduced strength. Practical controls are a restriction on heat input, a specified maximum interpass temperature, stringer rather than weave beads, and a final solution anneal where the component will see the most aggressive service. Post-weld heat treatment is not otherwise required, and this is a genuine fabrication advantage over 718 for large shop-fabricated equipment.

Dissimilar joints between the two alloys should be made with the more highly alloyed filler, which in practice means a nickel-chromium-molybdenum consumable such as ERNiCrMo-4 rather than a 718-matching filler, and where the joint will operate at temperature the procedure should include mechanical testing of the welded joint rather than of the parent metals alone. Neither alloy requires a post-weld heat treatment for dimensional stability in normal chemical plant construction, and neither should receive a generic stress relief that is not part of its qualified procedure.

Selection Rules: When to Choose 718, When C-276, and When Neither

The decision resolves into three questions that can be answered from the process data sheet without any material expertise: what load must the component carry at what temperature, what chemistry will it see, and will it be welded. If the load is high and the temperature is at or below about 650 °C, Inconel 718 is the leading candidate. If the chemistry is aggressive — reducing acid, chloride-rich, oxidising chloride or wet chlorine — Hastelloy C-276 is the leading candidate. If both statements are true at once, neither alloy is correct on its own.

Duty or component	Governing requirement	Recommended alloy	Why	Alternative
Turbine disc, compressor casing, blade hardware	strength to 650 °C	Inconel 718	precipitation-hardened to 1034 MPa min yield, oxidation resistant	Inconel 706 or 725 for lower or higher strength
High-temperature bolting and fasteners to 650 °C	strength plus relaxation resistance	Inconel 718	aged properties, low creep relaxation	Inconel X-750 for lower strength duty
Downhole hanger, wellhead, high-pressure tubing	strength plus sour service	Inconel 718, hardness controlled to 40 HRC max	high strength with NACE MR0175 compliance	Inconel 725 or 925 at lower strength
Cryogenic valve and pump components	toughness at low temperature	Inconel 718	retains ductility to cryogenic temperature	316L or Inconel 625 for lower strength duty
Chemical reactor handling hydrochloric acid	corrosion, reducing acid	Hastelloy C-276	Mo plus W resistance, 70–76 PREN	Hastelloy C-22 or C-4 if less severe
Flue gas desulphurisation absorber and duct	corrosion, chlorides, oxidising	Hastelloy C-276, often as wall-paper or overlay	resists mixed acid plus chloride	Inconel 625 overlay at lower severity
Wet chlorine, hypochlorite, chlorine dioxide plant	corrosion, oxidising plus chloride	Hastelloy C-276	the conventional alloy for these services	Titanium for chlorine without crevices
Pharmaceutical and fine chemical reactor with mixed acids	corrosion plus cleanness	Hastelloy C-276	handles mixed oxidising and reducing streams	Hastelloy C-22
High-strength wetted fastener in chlorinated seawater	strength plus severe corrosion	neither on its own	718 corrodes and C-276 is not strong enough	Inconel 725, or C-276 with a designed oversized section
Reactor needing 700 MPa yield and hydrochloric acid resistance	strength plus severe corrosion	neither	the requirements are mutually exclusive in this pair	clad plate: C-276 liner over a strong backing, or Inconel 725
Component at 800 °C carrying load in an oxidising gas	strength above 700 °C	neither	718 overages and C-276 precipitates phases	Inconel 617, 625 or a cobalt-based alloy
Hydrofluoric acid alkylation unit	reducing acid resistance	neither	HF requires a nickel-copper alloy	Monel 400 or Monel K-500

Table note: The recommendations are conventional selections for these duties and are based on the alloying systems and the corrosion and strength behaviour described above; the final selection in a project is normally governed by the process licensor's material selection diagrams and by the applicable code. The two rows marked "neither" are the practically important ones: where strength and severe corrosion are required together, the answer is almost always a composite construction — a corrosion-resistant liner, clad plate, or a weld overlay — rather than a single solid alloy, and where the temperature exceeds about 700 °C the answer is a different alloy family entirely. Our purchase specification guide sets out the clauses we recommend for an order of this type, and our comparison of Alloy 20 with C-276 covers the cheaper end of the same corrosion-resistance ladder.

The two exceptions to the rules above are worth stating explicitly. The first is sour service: 718 is the conventional choice for high-strength components in H2S-containing environments because NACE MR0175 / ISO 15156 permits it up to a hardness of 40 HRC, and in that specific service strength and corrosion resistance are not in conflict at moderate temperature. The second is the case where a small amount of strength is needed in a C-276 component: it is usually better to change the geometry or increase the section thickness than to change the alloy, because the corrosion resistance is the reason the alloy was selected and cold working it for strength reduces ductility without improving corrosion performance.

What Do 718 and C-276 Cost in 2026, and in Which Forms?

Hastelloy C-276 is the more expensive of the two per kilogram in every product form, because its 15–17 % molybdenum and 3.0–4.5 % tungsten are among the most costly alloying additions in commercial nickel alloys, whereas 718 is expensive mainly because of its processing and its niobium content. The gap is wide enough to decide applications in which both alloys are technically acceptable, and it should be understood at the specification stage rather than at the quotation stage.

Product form	Grade	Reference range, 2026, EXW Shanghai	Note
Round bar, 20–100 mm	Inconel 718, aged	USD 45–72/kg	heat treat cycle and niobium content drive the band
Round bar, 20–100 mm	Hastelloy C-276, annealed	USD 68–105/kg	molybdenum and tungsten content drive the band
Plate, 3–20 mm	Inconel 718	USD 48–78/kg	cut size and width affect the position
Plate, 3–20 mm	Hastelloy C-276	USD 72–118/kg	non-standard widths carry a premium
Seamless tube, 19–38 mm OD	Inconel 718	USD 62–110/kg	small quantities and thin walls at the top
Seamless tube, 19–38 mm OD	Hastelloy C-276	USD 88–155/kg	weld-quality and annealed tube at the upper end
Wire and welding consumables	ERNiFeCr-2 (718) and ERNiCrMo-4 (C-276)	quotation by diameter and pack	certification to AWS A5.14 / A5.11
Weld overlay, C-276 on carbon steel	cladding service	quotation by area and layer	first-layer dilution governs the price
Forging and near-net shape	either grade	quotation by drawing and weight	heat treat and test scope govern the price

Table note: Reference range only, 2026, EXW Shanghai, USD/kg, subject to movement in the LME nickel price and in the molybdenum, tungsten and cobalt markets; these figures are indicative and are not a quotation. Actual prices depend on quantity, specification, tolerances, test requirements, documentation, melting practice and delivery terms, and on whether the material is supplied from stock or from a mill heat with a specific chemistry. The premium for C-276 over 718 is concentrated in the alloying content, while the premium for 718 over a leaner nickel alloy is concentrated in the ageing cycle and the certified test scope, and the two premiums should be compared separately.

Three procurement points follow. First, the correct commercial comparison is total installed cost, not price per kilogram, and it usually favours the corrosion alloy where the alternative is a shorter life or an unscheduled shutdown, and favours 718 where the alternative is a heavier section or a lower allowable stress. Second, both alloys are good candidates for a composite construction — C-276 as a weld overlay or clad layer, 718 as the structural backing — and that route often satisfies a duty that neither solid alloy can meet. Third, both alloys are routinely counterfeited or substituted in the marketplace, and a delivered heat should be verified by PMI before release; our guide to detecting falsified mill certificates describes the checks that catch most substitutions, including the niobium and molybdenum content that distinguishes these two grades from cheaper look-alikes.

Standard Index

Standard	Title / scope	Covers	Form
ASTM B637	Precipitation-hardening and cold-worked nickel alloy bars, forgings and forging stock for moderate or high-temperature service (UNS N07718)	composition + mechanical	bar, forging, forging stock
ASTM B670	Precipitation-hardening nickel alloy plate, sheet and strip for high-temperature service (UNS N07718)	composition + mechanical	plate, sheet, strip
AMS 5662	Nickel alloy, corrosion and heat resistant, bars, forgings and rings, 718, solution heat treated, precipitation hardenable	mechanical + heat treatment	bar, forging, ring
AMS 5663	Nickel alloy 718 bars, forgings and rings, solution treated and precipitation heat treated	mechanical + heat treatment	bar, forging, ring
AMS 5596	Nickel alloy 718 sheet, strip and plate, solution heat treated, precipitation hardenable (latest edition)	mechanical + heat treatment	sheet, strip, plate
AMS 2750	Pyrometry — furnace instrumentation and heat treatment temperature control	heat treatment control	—
ASTM B575	Low-carbon nickel-molybdenum-chromium alloy plate, sheet and strip (UNS N10276)	composition + mechanical	plate, sheet, strip
ASTM B574	Low-carbon nickel-molybdenum-chromium alloy rod, bar and wire (UNS N10276)	composition + mechanical	bar, rod, wire
ASTM B622	Nickel-chromium-molybdenum alloy seamless pipe and tube (UNS N10276)	composition + mechanical	seamless pipe, tube
ASTM B619 / B626	Welded nickel alloy pipe and welded tube (UNS N10276)	composition + mechanical	welded pipe, tube
AMS 5530	Nickel alloy, corrosion and heat resistant, sheet, strip and plate, C-276 type (latest edition)	mechanical + heat treatment	sheet, strip, plate
ASME SB637 / SB670 / SB575 / SB574 / SB622	ASME BPVC Section II, Part B adoption of the corresponding ASTM nickel alloy specifications	composition + mechanical	all forms
GB/T 14992	Classification and designation of superalloys and intermetallic high-temperature materials — GH4169 designation	grade designation	all forms
GB/T 15007	Corrosion-resistant alloy designations — NS334 designation for the Ni-Mo-Cr family	grade designation	all forms
JIS G 4901 / G 4902	Corrosion-resistant and heat-resistant superalloy bars and plate — NCF 718 and NCF C276 designations	composition + mechanical	bar, plate
DIN 17744	Wrought nickel alloys — material standard naming the Werkstoff numbers 2.4668 and 2.4819	composition + tolerances	wrought forms
EN 10204	Metallic products — types of inspection documents (2.2, 3.1, 3.2)	inspection documents	all forms
GOST 5632	Corrosion-resistant, heat-resistant and heatproof high-alloy steels and alloys — grade list	grade designation	all forms
ASTM E8 / E8M and E21	Tension testing at room and elevated temperature	test method	—
ASTM E10 / E18	Brinell and Rockwell hardness testing	test method	—
ASTM E112	Determining average grain size	test method	—
ASTM E1476 / E572	Metals identification by PMI, and analysis of nickel alloys by X-ray spectrometry	test method	—
ASTM G48	Pitting and crevice corrosion resistance in ferric chloride solution	test method	—
ASTM G28	Detecting susceptibility to intergranular corrosion in nickel-rich alloys	test method	—
AWS A5.14 / A5.11	Nickel and nickel alloy bare welding electrodes and covered electrodes	welding consumables	wire, electrode
ASME BPVC Section IX	Welding, brazing and fusing qualifications	procedure qualification	—
NACE MR0175 / ISO 15156	Materials for use in H2S-containing environments in oil and gas production	material requirements	all forms

Table note: Standards are listed by number and scope; where an edition year is not quoted, the latest edition applies and the controlling edition is the one named on the purchase order. For Inconel 718 the mechanical requirements differ between the bar and forging standard and the plate and sheet standard, and between the AMS aerospace documents and the ASTM product standards, so the standard number must be stated on the order together with the product form and size. Verification of grade identity on delivery is normally performed by PMI to ASTM E1476, which distinguishes 718 from C-276 on the basis of niobium, molybdenum and tungsten content, and distinguishes both from cheaper stainless steels on the basis of nickel content. Cross-system equivalents such as the GH and NS designations of the GB system, the NCF designations of JIS, the Werkstoff numbers of DIN and the grades listed in GOST 5632 are indicative only and should be confirmed in the source standard before they are used as a contractual reference.

FAQ

Q1: Is Inconel 718 stronger than Hastelloy C-276?

Yes, by a very large margin, and the difference is a specified minimum rather than ordinary scatter. Inconel 718 in the solution-treated and aged condition is specified in AMS 5662 and AMS 5663 for bar, forgings and rings at a minimum tensile strength of 1240 MPa and a minimum 0.2 % yield strength of 1034 MPa, with a minimum hardness of 331 HB, while ASTM B637 sets a closely similar set of minima for the same grade. Hastelloy C-276 in the solution-annealed condition is a roughly 790 MPa tensile and 355 MPa yield class material, so aged 718 offers about three times the yield strength. The comparison is not, however, a fair fight, because the two alloys are bought for different purposes: C-276 is specified for corrosion resistance and accepts a low strength in exchange, while 718 is specified for strength and accepts a moderate corrosion performance in exchange. If a C-276 component needs more strength, cold working can raise its yield to roughly 800–1100 MPa, but the elongation falls sharply, the cold work is destroyed by welding, and the corrosion resistance is not improved. If an 718 component needs more corrosion resistance, no treatment will provide it and the grade must be changed.

Q2: Can Inconel 718 be used instead of Hastelloy C-276 in hydrochloric acid?

No. Hydrochloric acid is a reducing acid, and Inconel 718 relies for its corrosion resistance on a chromium-rich passive oxide film that requires an oxidising environment to form and to repair. In a reducing acid there is insufficient oxygen to maintain that film, and the alloy corrodes at a rate that is unacceptable for pressure equipment even at moderate concentration and temperature. Hastelloy C-276 contains 15–17 % molybdenum and 3.0–4.5 % tungsten, which allow it to resist reducing acids without depending on a passive film, and it is one of the standard materials for hydrochloric acid service across a wide range of concentrations and temperatures. The substitution is made more tempting by the fact that 718 is cheaper, stronger and more readily available in some product forms, but none of those advantages survive contact with the chemistry. This is precisely the class of error that the selection rules in this article are intended to prevent: strength is not a proxy for corrosion resistance, and a higher-strength alloy substituted into a chemical duty usually fails faster and more completely than the grade it replaced.

Q3: What is the maximum service temperature of Inconel 718 compared with Hastelloy C-276?

The two limits are set by different mechanisms, so the numbers are not directly comparable. Inconel 718 is limited by metallurgy: the gamma-double-prime precipitate that provides its strength is metastable and begins transforming to the stable delta phase above roughly 650 °C, so continuous load-bearing service is normally held at or below about 650 °C, with short excursions to about 700 °C being tolerated. Oxidation resistance extends much higher — the alloy resists scaling to around 800–900 °C — but that is not the constraint. Hastelloy C-276 resists oxidation to about 1040 °C on an intermittent basis, which is a higher oxidation limit than 718, but it is not a structural high-temperature alloy: its yield strength has already fallen to roughly 230–260 MPa at 650 °C, and holding it in the 650–1000 °C band precipitates carbides and intermetallic phases that reduce ductility and corrosion resistance. The practical result is that between 650 °C and 900 °C both alloys are on the wrong side of their own limitation, and a duty requiring strength in that band must move to a different grade such as Inconel 617 or 625.

Q4: Why is Hastelloy C-276 not age hardened?

Because the alloy contains nothing that can form a useful coherent precipitate, and the composition is deliberately arranged to keep the elements that would interfere below the levels at which they cause harm. Precipitation hardening requires an addition — aluminium, titanium or niobium in the nickel alloys — that can be taken into solution at high temperature and then precipitated as a fine, coherent phase during a controlled ageing cycle. Inconel 718 gets this behaviour from 4.75–5.50 % niobium plus tantalum, 0.65–1.15 % titanium and 0.20–0.80 % aluminium. Hastelloy C-276 contains none of these at a level that matters; instead it is built around 15–17 % molybdenum and 3.0–4.5 % tungsten, which provide corrosion resistance in solid solution. Its carbon content is held to 0.010 % maximum, one eighth that of 718, specifically so that carbide and intermetallic precipitation is suppressed rather than exploited. Applying an ageing treatment to C-276 therefore has no strengthening effect at all, and if the treatment is performed in the wrong temperature range it actively degrades the material by precipitating the very phases that reduce corrosion resistance and ductility, which is why any post-weld heat treatment on this grade must be a full solution anneal.

Q5: What is the ageing treatment for Inconel 718?

The standard treatment is a two-step ageing cycle applied after solution treatment, and it is specified for bar, forgings and rings in AMS 5662 and AMS 5663. The material is first solution treated at approximately 954–982 °C and rapidly quenched, which dissolves the gamma-double-prime and delta phases and conditions the alloy for ageing. It is then held at 720 °C for 8 hours, cooled in a controlled manner at roughly 50 °C per hour to the second step, held at 620 °C for a further 8 hours, and finally air cooled. The first step nucleates the precipitate; the second step completes it at a temperature where the precipitate is fine and coherent. The result is a yield strength in the region of 1034 MPa minimum compared with roughly 550–760 MPa in the solution-treated condition. The tolerances on the two temperatures, the permitted cooling rate and the furnace instrumentation requirements are all controlled by the specification, and where an aerospace or customer specification applies the pyrometry is normally performed to AMS 2750. Because the ageing cycle also acts as a stress relief, fabricated assemblies are normally welded in the solution-treated condition and then solution treated and aged once, rather than being aged twice.

Q6: Which alloy welds more easily, 718 or C-276?

Each is the easier one in a different sense. Inconel 718 is metallurgically more forgiving to weld: it is markedly less prone to solidification and strain-age cracking than other precipitation-hardening superalloys, and it welds readily by gas tungsten arc, gas metal arc and electron beam processes with ERNiFeCr-2 filler. What complicates 718 is the thermal history, because the joint must be solution treated and aged afterwards to recover parent-metal properties, and welding it in the already-aged condition or stress relieving it in the 650–870 °C band invites strain-age cracking in the heat-affected zone. Hastelloy C-276 is simpler in that respect, because no post-weld heat treatment is required at all; the weld is left in the as-welded condition and the material's corrosion performance depends on the weld and heat-affected zone remaining substantially in solution. What complicates C-276 is the heat input, because slow cooling or excessive energy input allows carbide and intermetallic precipitation that reduces corrosion resistance in the weld zone. In practice C-276 is the easier alloy for large shop-fabricated chemical equipment, and 718 is the easier alloy where a fully certified aerospace or turbine weld procedure already exists.

Q7: How do I tell 718 from C-276 in the warehouse?

By positive material identification, using X-ray fluorescence or optical emission spectrometry, and by nothing else. The two alloys are visually indistinguishable and have similar densities, so only composition distinguishes them. The confirming elements are also the ones that are easiest to measure: Inconel 718 contains 4.75–5.50 % niobium plus tantalum, 0.65–1.15 % titanium and 0.20–0.80 % aluminium, with molybdenum at only 2.80–3.30 %, while Hastelloy C-276 contains 15.0–17.0 % molybdenum and 3.0–4.5 % tungsten with effectively no niobium, titanium or aluminium. A reading of high molybdenum plus tungsten indicates C-276; a reading of niobium plus titanium indicates 718; and a reading of neither indicates that neither grade was delivered. PMI is performed to ASTM E1476, with ASTM E572 providing the X-ray spectrometric method for nickel alloys, and it verifies identity rather than full compliance, so it supplements rather than replaces the mill certificate. Where the material has already been formed into a component, the PMI should be taken on the component itself rather than on a retained coupon. Hangbo Alloy reports PMI results on every heat shipped and can supply a third-party verification by SGS, BV or TUV where the project requires it.

Q8: What is the Chinese, Japanese, German and Russian equivalent of each alloy?

Inconel 718 is designated GH4169 in the Chinese system, with the classification and designation rules set out in GB/T 14992, and it appears in the Japanese system as NCF 718 under the JIS superalloy standards such as JIS G 4901 and G 4902. Its German Werkstoff number is 2.4668, referenced in the DIN wrought nickel alloy material standard, and the corresponding Russian grade family is listed in GOST 5632. Hastelloy C-276 is designated NS334 in the Chinese corrosion-resistant alloy designation system published in GB/T 15007, appears as NCF C276 in the corresponding JIS designations, carries the German Werkstoff number 2.4819 for the NiMo16Cr15W composition, and corresponds to the ХН65МВ family listed in GOST 5632. Two cautions apply. The first is that a Chinese grade near this family, GH3128, is a different Ni-Cr-W-Mo refractory alloy and is not a substitute for C-276; assuming equivalence because the designation looks similar is a common and expensive error. The second is that cross-system equivalents are indicative for wrought product and are not identical clause by clause, so a specified design must be ordered against the requirements of the system named on the drawing, with the UNS number quoted in parallel rather than replaced.

Q9: Is Hastelloy C-276 more expensive than Inconel 718?

Yes, C-276 is the more expensive of the two per kilogram in every product form we handle, and the reason is entirely the alloying content. C-276 contains 15–17 % molybdenum and 3.0–4.5 % tungsten, both of which are costly additions whose market prices move independently of nickel, whereas 718 contains only 2.80–3.30 % molybdenum and approximately 5 % niobium, and its cost premium over a leaner nickel alloy comes mainly from the melting practice, the certified ageing cycle and the extent of mechanical testing required. As a reference, 2026 EXW Shanghai indications for round bar in the 20–100 mm range run at approximately USD 45–72/kg for aged 718 and USD 68–105/kg for annealed C-276, with plate and tube following the same ordering. Those figures are indicative only and move with the LME nickel price and the molybdenum and tungsten markets. The commercial conclusion, however, is not simply that 718 is cheaper: where the environment requires C-276, no saving from a cheaper alloy is real, and where the environment does not require it, the correct comparison is against a leaner corrosion alloy such as 625 or C-4 rather than against a high-strength alloy.

Q10: What is the PREN of each alloy, and does it matter?

The pitting resistance equivalent number is approximately 27–31 for Inconel 718 and approximately 70–76 for Hastelloy C-276, calculated as Cr + 3.3 (Mo + 0.5 W) from the standard composition ranges. PREN is a useful comparative indicator in chloride service, and the difference explains a practical observation: C-276 tolerates chlorinated seawater, oxidising chloride mixtures and crevices that will attack 718, and it is chosen for exactly that reason. Two qualifications limit how far the number can be pushed. First, PREN is a calculated typical value, not a standard requirement, and neither ASTM B637 nor ASTM B575 publishes a PREN acceptance limit, so it cannot be written as a specification clause without an agreed method and a defined acceptance figure. Second, PREN was developed for stainless steels and predicts resistance to chloride pitting and crevice attack; it says nothing about reducing-acid corrosion, which is the mechanism that actually distinguishes these two alloys and which is governed by molybdenum and tungsten content rather than by any simple index. Used as a screening comparison in chloride service it is helpful, and used as the sole selection criterion it will lead to the wrong answer.

Q11: Is there an alloy that combines 718 strength with C-276 corrosion resistance?

Not in one solid grade, which is why this pair produces so many genuinely difficult specification problems. The closest commercial answer is Inconel 725, UNS N07725, an age-hardenable nickel-chromium-molybdenum-niobium alloy that reaches yield strengths in the region of 690–860 MPa after ageing while carrying substantially more chromium and molybdenum than 718, and which is used for high-strength components in sour and chloride-bearing service. It sits between the two alloys rather than matching both. The more common engineering answers to the problem are not alloys at all: clad plate with a C-276 or C-22 liner over a carbon steel or alloy steel backing, weld overlay of the same corrosion alloy onto a structural base, a bolted hybrid design in which 718 carries the load and C-276 is the wetted material, or a change of process conditions that removes the corrosion or reduces the temperature. Where the difficulty is temperature rather than strength — a duty at 800 °C with a chemically aggressive environment — the answer is usually to separate the two requirements entirely, because no single alloy in this family handles both. Our technical team reviews these cases on the process data and will say plainly when a single grade will not work.

Q12: What information does Hangbo Alloy need to recommend one over the other?

We need the medium with its concentration and any contaminants, the operating temperature and pressure, whether dissolved oxygen or another oxidising species is present, whether chlorides or fluorides are present, whether crevices, deposits or stagnant zones will exist, the loads the component must carry and the code allowable stress, whether the part will be welded and in what sequence, and the product form and size required. With those data we can tell you which of the two governing questions applies — strength or corrosion — and whether either alloy is adequate at all, which is a question we answer honestly rather than by quoting the more expensive grade. Where the answer is that neither is correct, we will say so and propose the alternative, whether that is Inconel 725, a clad construction, a different alloy family, or a change of geometry. Send the process conditions through our contact page and we will respond with the recommended grade, the product standard, the condition, the heat treatment cycle and the verification requirements, together with a quotation for the material in the form you need.

Conclusion and Selection Rules

The choice between Inconel 718 and Hastelloy C-276 is decided by a single question: is the component defined by the load it carries, or by the chemistry it resists? Inconel 718 is the answer when load governs — it is precipitation hardened by the AMS 5662 two-step ageing cycle to a specified minimum yield strength of about 1034 MPa, it holds that strength to approximately 650 °C, and it is the standard high-strength alloy for turbine hardware, high-temperature fasteners, downhole equipment and sour service within the NACE MR0175 hardness limit. Hastelloy C-276 is the answer when chemistry governs — it is supplied solution annealed and quenched at around 1040–1120 °C, it is never aged, and its 15–17 % molybdenum plus 3.0–4.5 % tungsten give it approximately 70–76 PREN and the ability to resist hydrochloric acid, mixed oxidising and reducing acids, wet chlorine and chlorinated seawater that Inconel 718 cannot survive.

Three rules are worth keeping in front of the specification. First, decide which of the two governing requirements applies before comparing prices, because a cheaper alloy on the wrong side of that line is not a saving. Second, recognise the cases where neither alloy is correct — high strength combined with severe reducing-acid corrosion, and any load-bearing duty between roughly 650 °C and 900 °C — and solve them with a different alloy, a composite construction or a change of process rather than by compromising on one requirement. Third, state the UNS number, the product standard, the condition and the heat treatment on every order, because the same alloy name can denote a solution-treated material or an aged one, and the specified yield strengths of those two conditions differ by roughly a factor of 1.5.

Shanghai Hangbo Alloy Group Co., Ltd. supplies Inconel 718 and Hastelloy C-276 in bar, plate, sheet, strip, seamless tube, pipe, wire and forgings, with mill test certification to EN 10204 3.1, chemistry verification by XRF to ASTM E572, PMI to ASTM E1476, mechanical testing to ASTM E8/E8M and E21, hardness testing to ASTM E10 or E18, and third-party inspection by SGS, BV or TUV. Ageing of 718 is performed to the dual cycle of AMS 5662 with pyrometry to AMS 2750, and C-276 is supplied in the solution-annealed and quenched condition. Send your process conditions through our contact page and we will confirm the grade, the condition and the verification requirements, and quote the material with the testing scope stated explicitly.

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Shanghai Hangbo Alloy Group Co., Ltd. - China Supplier

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Ni: NI200-N6 | Monel: 400-502, K-500, R-405 | Inconel: 600-740H, X-750, 725 | Incoloy: 800-27-7MO | Hastelloy: C-276-HYBRID-BC1, N | Super Austenitic: 904L-AL-6XN | Chromium-Rich: Alloy 33 | High-Strength Stainless: Nitronic 50/60, PH13-8Mo | Chlorination: Alloy 45 | Nimonic: 75-263 | Haynes: 25-HR-160 | RA: 330/333 | Precision: 1J22-4J45 | High-Strength: 18Ni250-AerMet100 | Heating: Cr20Ni80/60 | Specialty: Alloy 20-602CA

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