Specifying Material Certifications

In aerospace and defense manufacturing, “material certification” is not a generic paperwork request—it is a controlled set of objective evidence that ties a delivered part back to a specific material lot, process route, and verification plan. A good certification package reduces program risk by proving that the raw material, additive manufacturing (AM) build, densification (e.g., HIP or PM-HIP), heat treatment, and post-processing (e.g., 5-axis CNC machining) were performed under qualified conditions, with traceability intact.

This article provides procurement- and engineering-ready guidance for specifying material certifications aerospace requirements in RFQs, purchase orders, and manufacturing plans—especially when the workflow includes powder bed fusion (PBF) such as DMLS/SLM, hot isostatic pressing, and regulated inspection (e.g., NDE, CMM). The goal is to help you request the evidence you actually need without over- or under-specifying, and to make the supplier’s compliance verifiable.

Mill certs and heat numbers

Mill test reports (MTRs) (often called mill certs) are the foundation of material traceability. For wrought or cast stock, the mill cert typically ties chemistry and mechanical properties to a heat number (also called a melt, heat, or cast lot). For powders used in AM or PM-HIP, the equivalent is the powder lot/batch with a manufacturer’s certificate and associated test data.

When you specify mill certs, avoid ambiguous language like “provide material certs.” Instead, specify exactly what you need to see and how it must map to your part identifiers.

What to require for wrought/cast feedstock:

1) Heat/lot identification on every relevant document. The MTR must show the heat number, material specification (e.g., ASTM/AMS), product form (plate, bar, forging, casting), and condition (solution treated, aged, annealed, etc.).

2) Positive mapping to delivered parts. Require the supplier to maintain and provide a traceability map that connects the heat number to your part number, serial number (or lot number), and work order/router. This is especially important when multiple heats are present in the same job.

3) Identification marking expectations. If you require physical traceability marking (e.g., vibro-etch, laser mark), define where marking is allowed, marking depth limits, and how marking will survive downstream processes. For critical rotating parts or fatigue-limited components, you may restrict marking to non-critical surfaces.

What to require for AM powders and PM-HIP powders:

Powder lot traceability should be treated like a “heat number equivalent.” Specify that the supplier must provide the powder manufacturer’s certificate and identify:

• Powder lot number and manufacturer (not just “Ti-6Al-4V”).
• Chemistry and interstitials (e.g., oxygen, nitrogen, hydrogen), because these drive ductility and fatigue performance.
• Particle size distribution (PSD) and acceptance limits used (e.g., D10/D50/D90, sieve cut).
• Powder reuse policy (number of reuses, blend ratio of virgin-to-reused powder, and how reuse is tracked by lot).
• Storage controls (sealed containers, humidity controls, inert handling where applicable).

Practical tip for RFQs: Ask suppliers to disclose whether powder is single-use or reused, and require that any reuse is documented by build (or by powder batch) with objective evidence. Reuse can be acceptable, but it must be controlled and consistent with your qualification basis.

Required test reports

Material certifications aerospace programs typically fail not because the supplier “didn’t provide certs,” but because the test basis wasn’t defined: What tests? From what specimens? At what frequency? To what acceptance criteria? And do results apply to the part as produced (after HIP, heat treat, and machining) or only to the raw input?

Specify test reports in layers that match your process route.

1) Chemistry and material condition

For wrought/cast feedstock, the MTR usually covers chemistry and may include mechanical properties. For powders, you may need both powder chemistry and final consolidated material chemistry (especially for PM-HIP). Clearly state whether you require chemical analysis on each lot and which elements are critical (e.g., O/N/H for titanium; C/S/P for steels; trace elements for nickel superalloys).

2) Mechanical properties tied to the correct processing state

Mechanical tests should reflect the condition of the delivered part (or the condition at which the part will be accepted). For example, in a PBF + HIP + heat treat workflow, tensile and fatigue-relevant properties can change significantly after HIP and subsequent heat treatment.

Define:

• Specimen type and orientation (e.g., build-direction vs. transverse for PBF; location within build volume).
• Heat treatment/HIP status of specimens (as-built, stress relieved, HIPed, solution treated/aged).
• Lot definition (one build, one powder lot, one HIP cycle, one heat treat load). If you don’t define a lot, you can’t define meaningful test frequency.

3) Additive manufacturing build records

If the part is additively manufactured, require a build record package that includes:

• Build ID and machine ID (serial number), with calibration status as evidence.
• Parameter set identification (approved parameter name/revision, not necessarily proprietary values).
• Environmental controls (e.g., oxygen level for inert gas systems, chamber pressure logs where applicable).
• In-process monitoring outputs when used as part of acceptance (melt pool monitoring, layer-wise imaging), including the criteria used to disposition anomalies.
• Build layout and part orientation (especially if mechanical properties are orientation dependent).

4) HIP and heat treatment reports

For Hot Isostatic Pressing (HIP), require a report that includes the cycle parameters (temperature, pressure, time) and the unique run ID, plus the furnace/load mapping. For PM-HIP (powder metallurgy + HIP consolidation), require both container/can traceability and the HIP cycle report, because the HIP cycle is the consolidation step that creates the billet.

For heat treatment, request:

• Furnace identification and calibration status (as applicable to your quality system).
• Load charts showing time/temperature and ramp/soak profiles for each load.
• Quench media and agitation controls where relevant (aluminum, steels).
• Lot/serial mapping from parts to heat treat load.

5) NDE and dimensional verification

When you write certification requirements, align NDE with the defect modes most likely for the process:

• CT scanning can be effective for internal porosity and lack-of-fusion characterization in AM, especially for complex internal passages.
• Dye penetrant (PT) and magnetic particle (MT) are common for surface-breaking discontinuities (material dependent).
• Ultrasonic (UT) may apply for thicker sections but can be challenging for intricate AM geometries.

Also require CMM or equivalent dimensional inspection reports tied to drawing characteristics, with clear identification of revision level, datums, and measurement system used.

Procurement-ready framing: Define which NDE methods are required for acceptance versus process monitoring. If CT scanning is requested, specify scan resolution, region of interest, acceptance criteria (porosity size/distribution), and the required deliverables (report, slice images, 3D volume, or pass/fail statement).

Traceability language

Traceability is where certification packages either hold up under audit—or fall apart. Your RFQ and PO should include explicit language defining what must be traceable, to what level, and what objective evidence is required.

Define the traceability chain in your requirements. A practical chain for aerospace/defense parts often includes:

Raw material / powder lot → work order/router → build ID (AM) → HIP run ID → heat treat load ID → machining traveler → NDE reports → final inspection report → Certificate of Conformance (CoC).

How to write traceability requirements that suppliers can execute:

1) State the unit of traceability. Is it by serial number, lot number, or batch? Critical flight hardware often needs serial traceability; lower-risk brackets may be lot traceable. If you don’t specify this, suppliers may default to lot traceability that is insufficient for your program.

2) Require unique identifiers on paperwork. Every report in the cert pack should reference at minimum: part number, revision, purchase order, quantity, and the supplier’s internal job/work order. For serialized parts, each report should list the serial numbers covered.

3) Control mixed lots. If a machining batch contains parts from different AM builds, different powder lots, or different heats, require segregation and documentation. “Commingling” is a common audit finding because it breaks the ability to associate test results and process records to specific parts.

4) Define record retention and accessibility. If you need records retained for a program duration, specify retention time and the expectation that records are retrievable by part serial number. This matters during field issues, FRACAS activity, or contract closeout.

Example RFQ/PO traceability clause (editable):

Supplier shall maintain full traceability from raw material heat number and/or powder lot number through all processing steps (AM build, HIP, heat treat, machining, and inspection) to each delivered part (serial or lot). Certification package shall include a traceability matrix mapping each part serial/lot to the applicable material lot, build ID, HIP run ID, and heat treat load ID. No commingling of parts from different lots without written approval.

Flow-down requirements

Flow-downs are where procurement and quality teams translate contract obligations into supplier-executable requirements. In defense and aerospace, flow-downs frequently reference AS9100 quality systems, special processes, and regulatory constraints such as ITAR and DFARS. The key is to flow down requirements that are measurable and verifiable, and to avoid over-scoping (which increases cost and lead time) unless the program truly demands it.

1) Define which suppliers must be qualified and how

Many programs require that special processes are performed by approved sources. If your organization maintains an Approved Supplier List (ASL), state that requirement and identify any mandatory sub-tier approvals. If you do not have an ASL, specify the minimum quality system expectations (e.g., AS9100-certified QMS) and require the supplier to disclose sub-tier processors.

2) Special process controls: HIP, heat treat, plating/coatings, and NDE

Special processes are those where the output cannot be fully verified by later inspection alone. For example, you can’t fully “inspect in” correct heat treatment after the fact without destructive testing. Therefore, your flow-down should require documented process control and objective evidence (charts, run IDs, calibration).

If your program requires accredited special processing (often associated with high-consequence hardware), state the accreditation requirement (e.g., NADCAP) for the relevant processes. If not required, still specify that the processor must be controlled and that reports must be provided.

3) ITAR and controlled unclassified information

If technical data or parts are export-controlled, your PO should clearly state ITAR applicability and any handling restrictions. Practical considerations include: limiting access to authorized personnel, controlling electronic data transfer, and ensuring sub-tier processors are eligible and approved before data is released.

4) DFARS and domestic sourcing / specialty metals considerations

When DFARS clauses apply, certifications may need to support origin and material compliance expectations. If your program requires domestic melt or other specialty metals compliance, explicitly request the supplier’s compliance statement in the CoC and require retention of objective evidence (e.g., MTRs indicating melt source). Keep the language aligned with your contract; do not ask suppliers to certify beyond what you can verify or what the contract requires.

5) Build-to-print acceptance and change control

Flow down revision control and change notification requirements. For AM in particular, define what constitutes a “change” that requires customer notification or re-qualification: parameter set revision, machine model changes, powder supplier change, HIP cycle change, or significant orientation/support strategy changes.

Procurement-ready flow-down checklist:

• CoC required for each shipment listing PO, part number, revision, quantity, and compliance statement.
• Sub-tier disclosure for special processes and NDE; no sub-tier changes without approval.
• ITAR/controlled data handling requirements clearly stated if applicable.
• Record retention time and retrieval requirements.
• Nonconformance notification and deviation request process defined (RMA/waiver process).

Storage and handling

Storage and handling requirements affect the integrity of material certifications because poor control can invalidate the assumptions behind the certs—especially for powders, reactive alloys, and parts awaiting NDE or final inspection.

1) Powder storage and handling (AM and PM-HIP)

PBF powders and PM-HIP powders can be sensitive to contamination and moisture pickup. Your specification should address:

• Container control: sealed, labeled containers with lot number and open date.
• Environmental limits: humidity/temperature controls, inert handling where required.
• Foreign material exclusion: dedicated tools, sieving controls, and cleaning methods.
• Reuse documentation: tracking of each powder lot through reuse cycles, including blend ratios and sieve results.

If powder properties are critical to your program, specify that powder must be handled per a documented procedure and that records are available for audit.

2) Raw stock and in-process material control

For wrought/cast stock, require segregation by heat/lot and clear physical labeling. The common failure mode is a shop cutting blanks from multiple heats and losing identity. If the part requires heat number traceability, require that heat number identity be maintained through cutting, fixturing, and machining travelers (e.g., bag-and-tag practices, barcode control).

3) Post-processing and finished part handling

After HIP, heat treat, and machining, parts are vulnerable to surface damage and corrosion. If NDE such as PT is required, specify handling that prevents false indications (e.g., avoid certain oils or residues). For titanium and nickel alloys, define cleanliness requirements where they affect inspection or assembly.

4) Calibration and inspection environment

Dimensional and NDE reports are only as good as the measurement controls. If your acceptance depends on CMM results, ensure the supplier’s process includes calibration control for measurement devices and stable inspection environments. You don’t need to dictate their entire metrology program, but you can require that calibration status is controlled and that inspection reports identify the equipment used.

Common mistakes

Most certification issues in aerospace and defense procurement are preventable. The mistakes below show up repeatedly in audits, first article reviews, and source inspections—especially when AM and densification are involved.

1) Requesting “certs” without defining the acceptance basis

Asking for “material certs and test reports” without defining which tests, which lots, and which processing states leads to incomplete or non-actionable documentation. Fix this by defining the lot structure (build/HIP/heat treat) and stating the required reports for each lot.

2) Confusing CoC with objective evidence

A Certificate of Conformance (CoC) is a statement of compliance; it is not the underlying evidence. For high-consequence hardware, require both: a CoC and attached objective evidence (MTRs, HIP charts, heat treat charts, NDE reports, dimensional results). Make sure your PO states what must be included in the shipment package versus retained and available upon request.

3) Losing traceability during post-processing

Traceability often breaks when parts move from AM to HIP to machining to inspection—sometimes across multiple facilities and sub-tiers. Prevent this by requiring a traceability matrix and by mandating that sub-tier reports include your part identifiers and the relevant run/load IDs.

4) Not specifying AM-specific controls

Traditional procurement language assumes the raw material is a single heat and the process is machining. AM adds variables: powder reuse, build orientation, machine parameter sets, and in-process monitoring. If you need consistency and repeatability, your certification requirements must explicitly request build IDs, parameter set revisions, powder lot controls, and the definition of a “build lot.”

5) Over-specifying accreditation or tests without program justification

Requiring every test and accreditation “just in case” can increase lead time and cost and may eliminate capable suppliers. Instead, align requirements to part criticality and failure modes. For example, requesting CT scanning for a simple non-critical bracket may be unnecessary, while it may be essential for an internal lattice or fluid manifold where internal defects are high risk.

6) Failing to define what happens when something is out of family

Parts, lots, or process records that fall outside defined limits need a clear path: containment, nonconformance documentation, customer notification, and disposition (rework, use-as-is deviation, or scrap). Include a requirement that the supplier must not ship nonconforming product without written approval and must provide objective evidence for any rework performed.

7) Ignoring storage/handling impacts on powder and parts

Powder contamination, moisture pickup, and poor segregation can undermine the validity of certification data. Define powder and in-process material handling expectations in the RFQ so suppliers plan for them, rather than improvising after award.

Putting it all together: a practical “cert pack” request

If you want a concise but complete requirement set, request a certification package that includes:

• CoC stating compliance to drawing/spec, PO, revision, quantity, and any regulatory clauses flowed down.
• MTR / powder certificate with heat or lot identification and chemistry.
• Traceability matrix mapping parts (serial/lot) to material lot, AM build ID (if used), HIP run ID, heat treat load ID.
• HIP and heat treat records (cycle reports/load charts).
• NDE reports (PT/MT/UT/CT) as required, with acceptance criteria references.
• Dimensional inspection report (CMM/inspection results) tied to drawing rev and characteristic list.
• Sub-tier certifications for any special processes, clearly referencing your part identifiers.

With those elements defined up front, suppliers can quote accurately, quality teams can verify compliance, and program managers gain predictable delivery with fewer document-driven surprises.