AMS 5662 vs ASTM B637: Ordering Alloy 718

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: AMS 5662 or ASTM B637 for Alloy 718?

Name AMS 5662 when the part is aerospace, when the drawing cites an AMS specification, or when the material is bar, forging or ring supplied aged; name ASTM B637 when the application is governed by a pressure vessel or process industry code, or where ASME acceptance is required. The chemistry is the same; the acceptance rules are not.

Key Takeaways

• The two systems specify the same alloy and different acceptance rules. AMS 5662 and ASTM B637 both describe Alloy 718 to UNS N07718, but they differ in melting method controls, testing frequency, sampling, marking and the documents that accompany the shipment.
• Product form decides which specification applies. AMS 5662, 5663 and 5664 cover bar, forgings and rings; AMS 5596 and 5597 cover sheet, strip and plate; ASTM B637 covers bar, forgings and forging stock, while ASTM B670 covers plate, sheet and strip.
• Condition is specified, not assumed. Material may be ordered aged and ready to machine, or in the solution-treated, precipitation-hardenable condition for forming and welding before the final ageing cycle.
• The specification revision letter is part of the requirement. AMS documents carry a revision letter that changes requirements; a drawing that cites AMS 5662 without a revision is an incomplete requirement.
• ASTM B637 and ASME SB637 are not interchangeable on paper. ASME adopts the ASTM specification into the boiler and pressure vessel code with its own scope, and the code edition that governs the project should be named.
• The mill certificate must match the specification named on the order. A certificate issued against a different specification, or against the specification without the revision, is a nonconformance even when the material is chemically correct.

The Two Specification Systems in Plain Terms

Alloy 718 is one of the most widely specified nickel alloys in the world, and the confusion around it is rarely about the material. The alloy is defined by UNS N07718 and by a chemistry that every supplier recognises. The confusion is about the paperwork: which specification, in which revision, for which product form, in which condition, with which tests, and with which certificate. Those five questions determine whether the delivered material is accepted or rejected, and they are the questions this article addresses.

The two systems that matter in practice are the SAE Aerospace Material Specifications, AMS, and the ASTM product specifications that are also adopted by ASME for pressure equipment. The AMS system originated in aerospace and carries the expectations of that industry: controlled melting practice, defined sampling, certified mechanical testing in the delivered condition, hardness limits, cleanliness requirements and a certificate of conformance that names the specification and its revision. The ASTM system is broader in application and is written for general industry and for pressure equipment; its product specifications define chemistry, mechanical properties, permissible variations, workmanship and testing, and they are adopted by ASME into the boiler and pressure vessel code and by other codes for process equipment.

A practical way to think about the difference is that AMS answers the question "is this material suitable for a flight-critical component made by a controlled process?", while ASTM B637 answers the question "is this material compliant with the product specification for high-temperature service, in a form that a pressure equipment code will accept?" A buyer who needs both — for example, an aerospace component that is also part of a pressurised system — should specify both, because the requirements are additive rather than alternative, and a supplier who is asked for one will not automatically provide the other.

The important consequence of this distinction is that a quotation given against "Alloy 718" without a specification is not a quotation for anything in particular. Two suppliers can quote the same price per kilogram for the same nominal alloy and deliver material with different melting routes, different testing, different documentation and different permissible chemistry ranges. The specification, the revision and the condition are what convert an alloy name into a purchase.

What AMS 5662 Actually Controls

AMS 5662 is the aerospace specification for Alloy 718 bar, forgings and rings supplied in the solution-treated and precipitation-hardened condition — in other words, material that is delivered ready to machine, having already been aged. It sets the chemistry, the melting method, the heat treatment cycle, the room-temperature tensile requirements, hardness limits and the certificate requirements for that material, and it is the specification most often cited on aerospace drawings that call for 718 in the aged condition.

The properties required by AMS 5662 are demanding relative to the annealed condition of other alloys: a minimum tensile strength in the region of 180 ksi (about 1240 MPa), a minimum 0.2 % yield strength in the region of 150 ksi (about 1030 MPa) and a minimum elongation of 12 %, all measured on the material in the precipitation-hardened condition and all achieved through the controlled ageing cycle rather than through alloy chemistry alone. Those figures are the reason Alloy 718 occupies its particular niche: it delivers the strength of a hardened alloy while remaining weldable, because the strengthening phase forms slowly and does not embrittle the heat-affected zone in the way that the gamma-prime strengthened alloys do.

The AMS family separates product form and condition rather than chemistry. AMS 5662 covers bar, forgings and rings in the aged condition. AMS 5663 covers bar, forgings and rings supplied in the solution-treated, precipitation-hardenable condition, which is the form used when the buyer intends to form, machine or weld the material and then perform the ageing treatment on the finished part. AMS 5664 covers bar, forgings and rings to premium quality requirements for the most demanding applications. Sheet, strip and plate are covered separately by AMS 5596 and AMS 5597. Because these designations divide the same alloy into different forms and conditions, a drawing that names an AMS number for the wrong product form is a substantive error rather than a clerical one.

Two features of the AMS system deserve attention when an order is placed. First, AMS documents are revised, and the revision is published as a letter; a requirement written as "AMS 5662" without a revision leaves the supplier free to work to any revision, and revisions have altered requirements historically. Second, the AMS system expects testing in the delivered condition with properly documented sampling, and it expects the certificate to identify the specification and revision; a certificate that reports only "718" or only the chemistry does not demonstrate compliance with an AMS requirement.

What ASTM B637 and ASTM B670 Control

ASTM B637 is the product specification for precipitation-hardening nickel alloy bars, forgings and forging stock for high-temperature service, and Alloy 718 is one of the alloys it covers. Its counterpart for flat product is ASTM B670, which covers plate, sheet and strip of the same alloy. Both are written as general product specifications: they define the composition ranges, the required mechanical properties in specified conditions, the permissible variations in dimensions and mass, the workmanship requirements, and the testing that must be performed, without the aerospace-specific overlay of melting practice and cleanliness controls that the AMS documents carry.

The role of these specifications in pressure equipment is what makes them commercially important. ASME adopts ASTM product specifications into the boiler and pressure vessel code, where they appear with the prefix SB — ASME SB637 for the bar and forging product, SB670 for flat product. A pressure vessel designed and stamped to ASME will normally require material to an ASME specification rather than to an ASTM one, even though the underlying requirements are closely related, because the code acceptance route depends on the specification being one that the code has adopted. Where a project is certified to the pressure equipment directive or to a national equivalent, the same logic applies through the material specification recognised by the notified body.

The practical differences between the ASTM route and the AMS route appear in four places. Melting practice is specified more tightly in the AMS documents, where consumable electrode or vacuum induction melting is required for many product forms. Testing frequency is defined differently, with the ASTM specification using lot definitions based on heat treatment charge and product size that do not always align with AMS sampling. Hardness is treated differently, with AMS imposing hardness limits as acceptance criteria in some forms and conditions. And marking and certification requirements differ, with ASME having its own rules on marking, and the code requiring the material test report to accompany the material and to be traceable to the marking on the product.

None of these differences changes the alloy. All of them change what a buyer must check on delivery, and each of them is a reason to state the specification, the revision where one applies, the product form, the condition and the acceptance code on the order rather than relying on the alloy name.

Chemistry: One Composition, Several Sets of Limits

The composition of Alloy 718 is essentially the same across the specifications that cover it, and the small differences that exist are in the trace elements and in how tightly they are controlled rather than in the major alloying elements. The table below sets out the composition with the elements that matter for specification compliance, and it identifies the standards in which the limits appear.

Element	Alloy 718, UNS N07718 (wt %)	Role in the alloy	Principal controlling standard
Ni	50.0–55.0	balance of the matrix; stabilises austenite	ASTM B637 / AMS 5662
Cr	17.0–21.0	oxidation and corrosion resistance; gamma-prime former	ASTM B637 / AMS 5662
Fe	balance	matrix constituent; reduces cost	ASTM B637 / AMS 5662
Nb + Ta	4.75–5.50	forms the strengthening phase with nickel and niobium	ASTM B637 / AMS 5662
Mo	2.80–3.30	solid-solution strengthener; corrosion resistance	ASTM B637 / AMS 5662
Ti	0.65–1.15	contributes to the strengthening phase	ASTM B637 / AMS 5662
Al	0.20–0.80	contributes to the strengthening phase	ASTM B637 / AMS 5662
Co	1.00 max	residual element, controlled	ASTM B637
C	0.08 max	controls carbide precipitation	ASTM B637 / AMS 5662
Mn	0.35 max	residual element	ASTM B637
Si	0.35 max	residual element	ASTM B637
P	0.015 max	trace element, tightly controlled for toughness	ASTM B637
S	0.015 max	trace element, tightly controlled for toughness	ASTM B637
B	0.006 max	grain boundary element, controlled in aerospace grades	AMS 5662
Cu	0.30 max	residual element	ASTM B637

Table note: Ranges summarised from the standards named in the final column (latest editions) and shown to identify the elements that govern specification compliance; the controlling limits are those of the specification, revision and product form named on the purchase order. The niobium plus tantalum content, the aluminium and titanium contents and the carbon content are the elements most often found outside specification on non-conforming material, and the trace elements phosphorus, sulphur and boron are the ones that distinguish aerospace grades from general product. Chemistry is normally verified in the mill by optical emission or X-ray spectrometry, and on delivery by PMI to ASTM E1476. Our purchase specification guide contains the clause-by-clause checklist we recommend for Alloy 718 orders.

The commercial significance of this table is that Alloy 718 is an alloy in which the composition is deliberately balanced rather than maximised. The niobium, titanium and aluminium contents determine the volume fraction of the strengthening phase and hence the aged properties; too little and the material will not reach its specified strength, too much and it becomes sensitive to the precipitation of undesirable phases during processing. The carbon content and the trace elements determine the toughness and the notch sensitivity of the finished part. This is the reason a specification that names only mechanical properties is unsafe for this alloy: a heat that meets the tensile requirement in a test coupon may still fail to meet the impact or fatigue requirement in the finished component, and the chemistry controls that are the difference are stated in the specification rather than being available to the buyer from a price list.

A related point concerns the melting route. Alloy 718 for critical applications is normally melted by vacuum induction melting followed by consumable electrode remelting, which controls segregation and reduces inclusions; material melted by a less controlled route may meet the chemistry limits and still not meet the cleanliness expectations that the aerospace specification embodies. Where a drawing names an AMS specification, the melting route is part of the requirement and it should not be substituted without written agreement, because it is one of the properties that the buying organisation is paying for.

Mechanical Properties and Acceptance Testing

The properties required of Alloy 718 depend on the condition in which it is supplied, and this is the point at which specifications that look similar produce very different purchase orders. Material supplied aged has specified properties that are verified before shipment; material supplied in the solution-treated, precipitation-hardenable condition has no aged properties to verify, because the ageing treatment has not yet been performed.

Specification and condition	Test temperature	Tensile strength	0.2 % yield strength	Elongation	Basis of the figure
AMS 5662, solution treated and aged	20 °C	1240 MPa (180 ksi) min	1035 MPa (150 ksi) min	12 % min	standard minimum
AMS 5663, solution treated, precipitation hardenable	as supplied	not specified in the supplied condition	not specified	not specified	properties established after ageing on the finished part
AMS 5664, solution treated and aged	20 °C	as AMS 5662 with premium quality controls	as AMS 5662	as AMS 5662	standard minimum
ASTM B637, precipitation hardened	20 °C	1240 MPa (180 ksi) min	1035 MPa (150 ksi) min	12 % min	standard minimum
ASME SB637, precipitation hardened	20 °C	as ASTM B637, as adopted by the code	as ASTM B637	as ASTM B637	standard minimum
ASTM B637, solution treated, typical	20 °C	~965 MPa (140 ksi)	~550 MPa (80 ksi)	~30 %	typical, not a standard minimum
ASTM B670 plate, precipitation hardened	20 °C	per the specification for the product form	per the specification	per the specification	standard minimum
Aged material, typical	650 °C	~1000 MPa (145 ksi)	~830 MPa (120 ksi)	~15–20 %	typical published data, not a standard minimum
Aged material, typical hardness	20 °C	—	—	—	~36–44 HRC typical

Table note: Values marked as standard minima are the published requirements of the specifications named in the row and are quoted to show their order of magnitude; the governing figure is the one stated in the specification, revision and product form named on the purchase order, because requirements vary between product forms and between revisions and because some specifications impose additional requirements such as hardness limits or grain size. Elevated-temperature figures are typical published values and are explicitly not standard minima; product specifications for bar and forging do not normally extend their room-temperature requirements to elevated temperature, and where design data at temperature are required they should be taken from the applicable code case or from a qualified test programme. Tensile testing is performed to ASTM E8/E8M, hardness testing to ASTM E10 or E18, and grain size determination to ASTM E112.

The sampling rules are where the two systems diverge most in practice. Both define a lot for testing purposes by heat and by heat treatment charge, but the definitions are not identical, and the number of tests required from a given quantity of material can differ between an AMS order and an ASTM order. This matters commercially because each test consumes material and requires laboratory time; a buyer who requires AMS-level testing frequency on a general industrial order pays for testing that the application does not need, while a buyer who accepts a reduced testing frequency on a critical application has accepted a gap in verification that will not be visible until a failure occurs.

There is also a distinction that catches buyers on receipt: the specification named on the mill certificate rather than the one on the purchase order. Where a supplier holds stock that was produced to a broader specification and certified accordingly, the material may be perfectly acceptable but the certificate will not match the requirement, and a purchaser operating under a quality system cannot accept it without a documented deviation. The remedy is procedural rather than metallurgical: state the specification and revision in the enquiry, require the certificate to quote the specification and revision, and check the certificate against the order before the material is released to production.

Heat Treatment: Cycles Written Into the Specification

Alloy 718 achieves its properties through a two-stage treatment: a high-temperature solution treatment that dissolves the strengthening elements and produces the correct grain structure, followed by a controlled ageing cycle that precipitates the strengthening phase. Both stages are defined by the controlling specification, and the ageing cycle in particular is not a shop-floor variable that a supplier may choose.

Stage	Customary cycle for Alloy 718	Purpose	Where it is defined	Practical note
Solution treatment	~968–1010 °C (1775–1850 °F), hold, rapid quench	dissolve secondary phases, set grain size	AMS 5662 / ASTM B637	quench rate affects subsequent ageing response
Primary ageing	~720 °C (1325 °F), hold about 8 h	nucleate the strengthening phase	AMS 5662 / ASTM B637	temperature uniformity governs property spread
Controlled cooling	furnace cool at about 55 °C/h to ~620 °C (1150 °F)	control precipitate morphology	AMS 5662 / ASTM B637	cooling rate is part of the specification
Secondary ageing	hold at ~620 °C to complete the cycle, then air cool	complete precipitation	AMS 5662 / ASTM B637	total hold time and rate are specified together
Stress relief after welding	lower-temperature treatment, cycle to be agreed	relieve residual stress without over-ageing	project specification	not identical to the ageing cycle
Re-ageing after repair welding	full ageing cycle repeated where permitted	restore properties in the repair zone	repair specification	requires a qualified repair procedure
Pyrometry and instrumentation	furnace survey, thermocouple placement, records	demonstrate cycle compliance	AMS 2750	the record is part of the certificate package
Vacuum or atmosphere control	controlled atmosphere where specified	prevent oxidation and contamination	AMS 5662 / customer specification	surface condition on delivery reflects this

Table note: The cycles shown are the customary treatments for Alloy 718 and indicate the shape of the specification requirement; the mandatory temperatures, tolerances, hold times and cooling rates are those stated in the controlling specification, revision and product form named on the purchase order, and they must be applied by a heat treater whose furnace instrumentation complies with the pyrometry requirements of the applicable aerospace specification where one is invoked. Alloy 718 is not a simple solution-and-age alloy in the sense that many heat treaters expect, because the cooling rate between the two ageing stages affects the properties achieved, so the cycle should be treated as a single controlled sequence rather than as two independent holds.

Three ordering points follow from this table. First, state who performs the ageing treatment. Material ordered aged is aged at the mill or at a qualified heat treatment facility and certified in the aged condition; material ordered in the precipitation-hardenable condition is aged after fabrication, which means the buyer owns the heat treatment risk and must specify the cycle and the pyrometry requirements. Second, where the component is welded, decide before the order whether the assembly will be aged after welding, because that decision changes the condition to be purchased and the welding procedure to be qualified. Third, require the heat treatment records with the certificate, because a certificate that reports properties without the cycle cannot be checked against the specification and is of little value if the material is later questioned.

For welding, the practical guidance is that Alloy 718 is one of the more weldable high-strength nickel alloys, but that welding in the aged condition is normally avoided and that the material should be joined in the solution-treated or annealed condition and aged afterwards where the design permits it. Where ageing of a large fabrication is impractical, the welding procedure and any local heat treatment should be qualified to demonstrate the properties achieved. Our Alloy 718 versus A286 comparison covers the alternative alloys that are used when post-weld ageing of the assembly is not possible.

Specification Comparison: AMS, ASTM and ASME Side by Side

The four specifications that cover most Alloy 718 orders differ in scope and in the administrative requirements they impose. The table below compares them on the points that a buyer must check, and it is intended to be read before a specification is written onto a drawing rather than after a quotation has been received.

Aspect	AMS 5662 / 5663 / 5664	ASTM B637 / ASME SB637	AMS 5596 / 5597	ASTM B670 / ASME SB670
Product form	bar, forgings, rings	bar, forgings, forging stock	sheet, strip, plate	plate, sheet, strip
Condition covered	aged, or precipitation hardenable	both conditions, as ordered	per the designation	both conditions, as ordered
Origin of the system	aerospace	general industry and pressure equipment	aerospace	general industry and pressure equipment
Melting and quality controls	specified, including remelting practice	not specified to aerospace depth	specified	not specified to aerospace depth
Acceptance in ASME code work	not an ASME specification	adopted by the code as SB	not an ASME specification	adopted by the code as SB
Revision control	letter revisions, frequently issued	edition years	letter revisions	edition years
Typical certificate expectation	certificate of conformance naming the specification and revision	mill test report to EN 10204 3.1	certificate of conformance	mill test report to EN 10204 3.1
Typical application	aerospace components, critical rotating parts	pressure equipment, process plant, general engineering	aerospace sheet and plate fabrications	process plant plate, vessels, general fabrication
Effect of using the wrong one	potential rejection of material that is chemically correct	additional cost and lead time for tests the application does not require	as above	as above

Table note: The comparison is drawn from the scope of the standards named in the columns and is intended to show the administrative differences that determine acceptance; it is not a substitute for reading the specification invoked by the drawing. AMS designations divide the same alloy by product form and condition, and they carry revision letters, so the designation and revision must both be confirmed against the current SAE AMS index before the requirement is issued. ASTM product specifications are adopted by ASME with the SB prefix, and where a project is designed and stamped to the ASME code the ASME designation should appear on the order in addition to the ASTM designation. Our EN 10204 certificate guide explains the inspection documents that accompany material under each route.

The most common specification error in practice is the use of an AMS bar specification for a flat product requirement, or the reverse. A drawing that calls for AMS 5662 plate cannot be satisfied by any supplier, because AMS 5662 does not cover plate; the flat product designations are different, and if the drawing is a legacy document the specification may need to be corrected rather than satisfied. Identifying this at the enquiry stage costs nothing; identifying it at the goods-in stage costs a rejection, a schedule delay and a rework of the drawing that should have happened first.

The second most common error is the omission of the condition. Alloy 718 is ordered in the aged condition when the part will be machined from solid without subsequent forming or welding, and in the solution-treated, precipitation-hardenable condition when the part will be formed or welded and aged afterwards. A quotation that does not state which of these was quoted, and a purchase order that does not state which was intended, leaves the specification open, and the material that arrives may be in the condition the supplier finds most convenient rather than the one the process requires.

Choosing and Ordering: A Decision Table and Cost Reference

The decision of which specification to name follows from the application and from the code that governs it. The table below sets out the cases that account for most orders, and the price table that follows gives an indication of the commercial consequence of choosing a stricter route.

Situation	Specification to name	Reason
Aerospace drawing citing an AMS document	the AMS designation plus its revision	the drawing defines the requirement
Component in an ASME-stamped pressure vessel	ASME SB637 or SB670, with the ASTM designation	code acceptance route
General industrial bar or forging, no code	ASTM B637	proportionate testing and documentation
Plate or sheet for a process vessel	ASTM B670, or the AMS flat-product designation where aerospace applies	product form coverage
Both aerospace and pressure equipment requirements apply	both specifications	the requirements are additive
Material for forming and welding, aged afterwards	the precipitation-hardenable condition of the relevant specification	the ageing cycle belongs to the fabricator
Replacement component in an existing plant	the specification of the original equipment documentation	consistency with the installed design code
Stock material from a distributor	require the certificate to quote the specification, revision and condition	certificates frequently cite only the alloy

Table note: The recommendations are conventions drawn from the way these specifications are applied in the aerospace, pressure equipment and general engineering sectors; the governing requirement is always the specification invoked by the drawing, the design code or the client, and where more than one applies the stricter requirement governs. Where a specification is written into an existing drawing and cannot be satisfied by any product form, the drawing should be corrected through the engineering change process rather than worked around, because a nonconformance created at the drawing stage will be discovered at goods-in.

Product form	Condition	Reference range, 2026, EXW Shanghai	Note
Round bar, 20–150 mm	aged, ASTM B637	USD 45–72/kg	general industrial certification
Round bar, 20–150 mm	aged, AMS 5662	USD 58–92/kg	AMS testing, revision control and conformance certificate
Round bar, 20–150 mm	solution treated, precipitation hardenable	USD 42–68/kg	ageing performed after fabrication
Forging stock	aged or as-forged	quotation by size and quantity	forging route and test plan drive the price
Plate, 5–50 mm	aged or precipitation hardenable	USD 48–80/kg	cut size and thickness tolerance affect the band
Sheet, 0.5–3 mm	per AMS flat-product designation	USD 65–110/kg	thin gauge and flatness requirements
Wire and bar for fastener stock	aged	USD 60–95/kg	diameter tolerance and straightness
Welding filler, ERNiFeCr-2	bare wire and covered electrode	quotation by diameter and pack	certified to AWS A5.14 / A5.11

Table note: Reference range only, 2026, EXW Shanghai, USD/kg, subject to the LME nickel price and to the niobium, molybdenum and cobalt markets; these figures are indicative and are not a quotation. The premium for an AMS route over a general specification route reflects the additional testing, the melting practice requirements, the revision control and the certification rather than a different alloy, and it typically falls in the region of 15–30 % for the same product form. Buyers should also account for the cost of the ageing treatment when material is purchased in the precipitation-hardenable condition, which is performed on the finished part and therefore does not appear in the material price. Our machining guide covers the fabrication economics of the aged and unaged conditions, and other materials and specification articles cover the wider family of nickel alloy grades.

Standard Index

Standard	Title / scope	Covers	Form
AMS 5662	Nickel alloy, corrosion and heat resistant, bars, forgings and rings, 718, solution treated and precipitation hardened	composition + mechanical + heat treatment	bar, forging, ring
AMS 5663	Nickel alloy, corrosion and heat resistant, bars, forgings and rings, 718, solution treated, precipitation hardenable	condition + heat treatment	bar, forging, ring
AMS 5664	Nickel alloy, corrosion and heat resistant, bars, forgings and rings, 718, premium quality	composition + mechanical + quality controls	bar, forging, ring
AMS 5596 / AMS 5597	Nickel alloy, corrosion and heat resistant, sheet, strip and plate, 718	composition + mechanical	sheet, strip, plate
AMS 2750	Pyrometry	furnace and instrumentation control	test method
ASTM B637	Precipitation hardening nickel alloy bars, forgings and forging stock for high temperature service	composition + mechanical	bar, forging, forging stock
ASTM B670	Precipitation hardening nickel alloy plate, sheet and strip for high temperature service	composition + mechanical	plate, sheet, strip
ASME SB637 / SB670	ASME adoption of ASTM B637 and B670 for pressure equipment	composition + mechanical + marking	bar, forging, plate, sheet
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 E139	Conducting creep, creep-rupture and stress-rupture tests	test method	—
ASTM A370	Mechanical testing of steel products (referenced for test methods)	test method	—
EN 10204	Metallic products — types of inspection documents (2.2, 3.1, 3.2)	inspection documents	all forms
ISO 9001	Quality management systems	system requirement	all forms

Table note: Standards are listed by number and scope; AMS documents carry revision letters and ASTM documents carry edition years, and where a revision or edition is not quoted in this table the current issue applies, with the controlling issue being the one named on the purchase order. The distinction between a specification that defines the product and a specification that defines a method or a system should be kept clear when a requirement is written: a certificate citing ISO 9001 demonstrates that the supplier operates a quality system, and it says nothing about whether the material meets the product specification.

FAQ

Q1: What is the difference between AMS 5662 and ASTM B637?

Both specifications cover Alloy 718 to UNS N07718 and both define its chemistry and its mechanical properties, but they belong to different systems and carry different administrative requirements. AMS 5662 comes from the aerospace materials system and covers bar, forgings and rings in the solution-treated and precipitation-hardened condition, with controlled melting practice, defined sampling and a certificate of conformance that names the specification and its revision. ASTM B637 is a product specification for precipitation-hardening nickel alloy bar, forgings and forging stock for high-temperature service, written for general industry and adopted by ASME for pressure equipment. Where a drawing or a design code names one of them, that is the requirement; where a buyer is free to choose, the choice should be made on the acceptance route the end user needs rather than on price alone.

Q2: Can I substitute ASTM B637 material for an AMS 5662 requirement?

Not without written agreement, even though the alloy and much of the chemistry are identical. The substitution changes the melting practice controls, the sampling and testing frequency, the marking requirements and the documentation that accompanies the material, and each of those is part of what the aerospace requirement is buying. In a quality-system environment the substitution also requires a documented deviation approved by the design authority, because the drawing cites a specification that the delivered material does not meet. Where the material is technically equivalent and the application genuinely does not require the aerospace route, the correct process is to change the requirement through the engineering change system rather than to accept material that does not conform to the drawing. Our position on substitutions is that the buyer should be told what the difference is and should make the decision in writing.

Q3: Why does AMS 5662 have a revision letter but ASTM B637 has an edition year?

Because the two systems revise on different principles. The aerospace system issues letters to individual specifications as requirements change, so that a drawing can cite the exact revision that was current when the design was released and can be updated deliberately. The ASTM system works by edition years, with each edition absorbing all changes since the previous one. For the buyer the practical consequence is the same in both cases: the requirement should be stated precisely enough that the supplier cannot deliver to a different set of rules than the one intended. Where a drawing cites AMS 5662 without a revision letter, the requirement is ambiguous, and the material received may conform to a revision other than the one the design assumed.

Q4: Should I order Alloy 718 aged or in the precipitation-hardenable condition?

Order it aged when the part will be machined from solid without forming or welding, because the properties are then verified at the mill and the buyer carries no heat treatment risk. Order it in the solution-treated, precipitation-hardenable condition when the part will be formed, bent or welded before the final heat treatment, because the ageing treatment has to be performed after those operations and must be done on the finished component. The decision therefore belongs to the manufacturing plan rather than to the purchasing department, and it should be made before the material is ordered. Where the decision is made late, the common outcome is aged bar that then has to be welded, which requires either a local heat treatment or a qualified procedure that accepts lower properties in the weld zone.

Q5: What does the ageing cycle for Alloy 718 involve?

The customary treatment is a two-step cycle: a primary hold at about 720 °C for approximately eight hours, a controlled furnace cooling at roughly 55 °C per hour to about 620 °C, and a secondary hold at that temperature to complete the precipitation, followed by air cooling. The cooling rate between the two stages is part of the cycle rather than an incidental detail, because it governs the morphology of the strengthening phase and therefore the properties achieved. The exact temperatures, tolerances, hold times and cooling rates are defined by the controlling specification and by the pyrometry requirements of the applicable aerospace standard, which govern furnace surveys and thermocouple placement. This is why the heat treatment records are as important as the property results on the certificate.

Q6: How do I know the mill certificate is genuine?

Check four things. First, that the certificate names the specification and the revision or edition on the order, not merely the alloy. Second, that the heat number on the certificate matches the marking on the material, and that the marking method and content comply with the specification. Third, that the test results are accompanied by the conditions under which they were obtained, because a tensile result without its heat treatment condition cannot be compared with the requirement. Fourth, that the certificate is issued with the correct document type to EN 10204 where the order requires it, 3.1 from the manufacturer or 3.2 countersigned by an independent inspector. Where doubt remains, PMI to ASTM E1476 confirms the grade identity on the delivered product, and independent mechanical testing can be arranged on a sacrificial sample.

Q7: Does ASME accept ASTM B637 material?

Yes, through the ASME adoption of the ASTM specification, in which the product specification appears with the SB prefix and is subject to the code's own requirements on marking, documentation and, where applicable, additional testing. For practical purposes the buyer of a code-stamped pressure component should state the ASME designation on the order, because the acceptance route at the fabricator and at the authorised inspector runs through the code. Where material is purchased against ASTM B637 and used in code work, the fabricator must be satisfied that the material meets the code requirement, and that check is simpler if the material was ordered against the code specification in the first place. Our Inconel range is supplied with the ASTM and ASME designations both stated on the certificate where the order requires it, so incoming inspection can verify the code route directly against the document rather than inferring it from the chemistry.

Q8: Why is Alloy 718 so widely used instead of a gamma-prime strengthened alloy?

Because it achieves high strength while remaining weldable and reasonably formable, which most high-strength nickel alloys do not. The strengthening phase in Alloy 718 forms relatively slowly, so the heat-affected zone of a weld does not suffer the rapid precipitation and cracking that the gamma-prime strengthened alloys experience, and ageing after welding restores properties across the joint. That combination of strength, weldability and moderate cost explains its use in aerospace structures, fasteners, gas turbine components and process plant. The trade-off is that its useful temperature range is lower than that of the gamma-prime alloys, with strength falling away above about 650 °C, so above that temperature the selection moves to Alloy 617, Waspaloy or a Nimonic grade, and our high-temperature nickel alloy range covers the grades we supply for those duties.

Q9: What happens if the drawing cites a specification for the wrong product form?

Nothing can be delivered against it, because the specification does not cover that form, and the error has to be corrected through the engineering change process. The common cases are AMS bar specifications cited for plate and sheet, and flat-product designations cited for bar, forgings or rings. Where the error is discovered at the enquiry stage it costs a drawing revision; where it is discovered at goods-in it costs a rejection, a delay and a nonconformance raised against a supplier who delivered exactly what was technically possible. We check every enquiry against the product form covered by the specification named, and we say so before quoting where the requirement as written cannot be met. Correcting the drawing at that stage costs one revision; discovering the problem at goods-in costs a rejection, a schedule delay and a supplier nonconformance for material that was produced exactly as the order described it.

Q10: Does the melting method matter for Alloy 718?

It matters for cleanliness, segregation and the consistency of properties in critical applications, which is why the aerospace specifications control it and why vacuum induction melting followed by consumable electrode remelting is the conventional route for rotating and structural components. Material melted by a less controlled route can meet the chemistry and the tensile requirements while containing inclusions or segregation patterns that reduce fatigue life and toughness in service. Where a drawing names an AMS specification, the melting practice is part of the requirement and should not be substituted without engineering agreement. For general industrial applications where the material is not fatigue-critical, the wider range of acceptable melting routes is one reason a general specification route costs less than an aerospace one.

Q11: How long does it take to obtain Alloy 718 to an AMS specification?

Lead time depends on whether the material is held in stock in the required form and condition, and on the testing that the specification requires. Bar in common diameters is frequently available from stock with a general industrial certificate, and obtaining it with AMS certification may require either a specific heat produced to the aerospace melting practice or additional testing on stock material, both of which extend the lead time. Forging stock and non-standard sizes are made to order and the lead time is governed by the mill programme. Our practice is to state the expected lead time with the specification route assumed in the quotation, because quoting a single lead time for both routes conceals the difference that matters to the project.

Q12: What is the cost difference between the two specification routes?

For the same product form, an AMS route typically costs 15–30 % more than a general ASTM route, and the difference is accounted for by the melting practice controls, the additional testing and sampling, the revision control and the certificate of conformance rather than by a difference in the alloy. On a large order the absolute difference is significant, and it is worth confirming with the design authority whether the aerospace route is genuinely required before the order is placed. Where it is required, it should not be economised on, because material that does not conform to the requirement is of no value to the application regardless of its price. Where it is not required, specifying it adds cost to every unit produced without adding assurance that the application needs.

Conclusion and Selection Rules

Choosing between AMS 5662 and ASTM B637 is a decision about the acceptance route rather than about the alloy. The same Alloy 718, to the same UNS number, is covered by both systems, and the difference lies in the melting practice controls, the sampling and testing requirements, the marking and the documentation that a delivered lot must carry. Name the AMS route when the drawing or the end user requires aerospace certification, when the part is fatigue-critical or rotating, or when a certificate of conformance naming the specification and its revision is required. Name the ASTM and ASME route when the component is governed by a pressure equipment code or by a general engineering specification, where the code's acceptance route is what the fabricator and the inspector will follow.

Three rules are worth stating. State the specification, its revision or edition, the product form and the condition on every order, because each of the four changes what is delivered. Do not accept a substitution between the two systems without a written deviation, because the difference is a requirement difference rather than a price difference. And confirm the product form covered by the specification before issuing the requirement, because a specification that does not cover the form ordered cannot be satisfied by any supplier and the error belongs to the drawing rather than to the mill.

Shanghai Hangbo Alloy Group Co., Ltd. supplies Alloy 718 in bar, plate, sheet, seamless tube, wire and forgings, with certification to AMS 5662, AMS 5663, ASTM B637, ASTM B670 and the corresponding ASME designations, mechanical testing to ASTM E8/E8M, hardness testing to ASTM E10 or E18, grain size determination to ASTM E112, PMI to ASTM E1476, and inspection documents to EN 10204 3.1 or 3.2 with third-party witness by SGS, BV or TUV. Send your drawing requirement and product form through our contact page and we will confirm the specification route, the condition and the documentation, and quote accordingly.

Contact & Complete Product Range

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

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

All Grades

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

Product Forms: Bars(6-500mm) | Tubes(OD 6-610mm) | Plates(0.1-100mm) | Forgings | Welded Pipes | Fittings | Wire(0.05-10mm) | Strip(0.02-4.0mm)

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