Procuring superalloy components requires detailed specifications that communicate your engineering requirements clearly and completely to the manufacturer. Incomplete or ambiguous specifications lead to delays, cost overruns, and components that don't meet your needs. This checklist covers every element that should be addressed when specifying superalloy castings, forgings, and machined components.
1. Material Specification
Define the alloy grade using recognized standards rather than trade names alone. Specify the UNS number (e.g., N07718 for Inconel 718) and the applicable material specification (e.g., AMS 5663, ASTM B637, or customer-specific). Include any additional requirements beyond the base specification such as restricted chemistry ranges, vacuum melting requirements, or specific melting practice (VIM, VAR, ESR). If you need help selecting the right alloy, CastAlloy's Interactive Superalloy Selection Guide provides a systematic framework, or our metallurgical engineers can advise based on your specific operating conditions.
2. Heat Treatment Condition
Specify the required heat treatment condition explicitly. For precipitation-hardened alloys like Inconel 718, this means defining the solution treatment temperature, cooling method, and aging cycle (or referencing a specification like AMS 5663 that defines these). For solid-solution alloys, specify the annealing temperature and cooling rate. For titanium alloys, specify whether mill annealed, solution treated and aged, or beta annealed condition is required. The heat treatment directly determines the mechanical properties, so an incorrect or ambiguous heat treatment specification is one of the most common sources of non-conforming parts. See our guide on superalloy heat treatment for details on each alloy's requirements.
3. Mechanical Property Requirements
Define minimum mechanical properties including tensile strength, yield strength (0.2% offset), elongation, and reduction of area at specified test temperatures (room temperature and/or elevated temperature). For fatigue-critical applications, specify fatigue test requirements (test type, stress ratio, temperature, minimum cycles to failure). For creep-critical applications, specify stress-rupture requirements. For sour service applications, specify maximum hardness per NACE MR0175 (see our NACE compliance guide). Reference the applicable test standards (ASTM E8 for tensile, ASTM E139 for stress-rupture, ASTM E23 for impact).
4. Dimensional Requirements
Provide a fully dimensioned engineering drawing with geometric dimensioning and tolerancing (GD&T) per ASME Y14.5. Identify critical dimensions that must be held to tighter tolerances than the general tolerance block. For castings, specify the applicable casting tolerance standard (e.g., investment casting industry standard, MIL-STD-2175, or customer-specific). For forgings, specify machining stock allowances on forged surfaces. Identify datum features and inspection reference points. Include surface finish requirements (Ra microinches) on critical surfaces.
5. Non-Destructive Testing (NDT)
Specify required NDT methods, acceptance criteria, and applicable standards. Common requirements for superalloy components include radiographic (X-ray) inspection per ASTM E94 with acceptance per ASTM E2104 or customer-specific criteria, fluorescent penetrant inspection (FPI) per ASTM E1417 with acceptance per ASTM E433, ultrasonic inspection per ASTM A388 for forgings or ASTM E2375 for castings, and dimensional inspection reporting per first article inspection (FAI) requirements such as AS9102. Define the extent of inspection: 100% of production, statistical sampling, or first article only. See our NDT services guide for details on available methods.
6. Manufacturing Process Requirements
Specify required or preferred manufacturing processes if they are critical to your application. For castings: specify vacuum or air melt, HIP requirements, and any post-casting process restrictions. For forgings: specify open-die vs. closed-die, minimum reduction ratio, and grain flow direction requirements. For machining: specify prohibited processes (e.g., no EDM on fatigue-critical surfaces), surface integrity requirements, and any restrictions on cutting fluids. Refer to our Casting vs Forging comparison for guidance on process selection.
7. Quality Documentation
Define the documentation package required with shipment. Typical requirements include a certificate of conformance (CoC) certifying compliance with the purchase order, material test reports (MTR) with chemistry and mechanical properties per heat/lot, heat treatment records with furnace charts, NDT reports for all specified inspections, dimensional inspection reports (CMM data for critical features), and PPAP documentation if required for production part approval. Specify the quality system standard the supplier must hold (ISO 9001:2015, AS9100, IATF 16949, etc.).
8. Traceability and Marking
Specify traceability requirements: heat traceability (all components from the same material heat tracked together), lot traceability (all components processed together tracked as a lot), or individual piece traceability (each component individually serialized and tracked). Define part marking requirements including content (part number, serial number, material heat number), method (vibro-etch, laser mark, ink stamp), and location. For some applications, marking method restrictions apply (e.g., no stamping on fatigue-critical surfaces).
9. Packaging and Shipping
Specify packaging requirements to prevent damage during transit, especially for machined surfaces and precision features. Define preservation requirements for corrosion-susceptible alloys. Specify shipping method, insurance requirements, and delivery terms (FOB origin, delivered, etc.).
10. Regulatory and Industry Compliance
Identify any regulatory requirements applicable to your component including ASME Boiler and Pressure Vessel Code (nuclear or pressure equipment), API standards (oil and gas), FAA/EASA airworthiness requirements (aerospace), NACE MR0175/ISO 15156 (sour service), and ITAR/EAR export control requirements (defense). These requirements may impose additional material, process, and documentation obligations beyond the base engineering specification.
Get Specification Support from CastAlloy
CastAlloy's engineering team routinely assists customers in developing complete component specifications that ensure the finished product meets all performance, quality, and regulatory requirements. If you have a component concept but need help developing the full specification, contact us for a no-cost engineering consultation. We can advise on material selection, manufacturing process, quality requirements, and specification completeness based on 30+ years of experience producing superalloy components for the world's most demanding industries.