Qualification and Certification of AM Components

## The Qualification Challenge Conventional metal components have decades of service history, well-established material specifications, and suppliers with proven quality systems. AM introduces new variables — powder batch variations, machine-to-machine differences, build orientation effects, and novel defect types — that existing material specifications were not designed to address. Qualification answers the question: how do we demonstrate that an AM process produces parts that are safe and reliable for their intended service? ## Aerospace Standards Aerospace has led AM qualification because the industry has both the economic incentive (high-value, low-volume parts) and the regulatory framework to drive adoption. ### SAE AMS Standards | Standard | Scope | |----------|-------| | AMS 7000 | General requirements for L-PBF metal parts | | AMS 7002 | Qualification of L-PBF machines | | AMS 7003 | L-PBF of Ti-6Al-4V (powder, process, properties) | | AMS 7004 | L-PBF of UNS N07718 (Inconel 718) | | AMS 7010 | Wire DED of Ti-6Al-4V | | AMS 7011 | EB-PBF of Ti-6Al-4V | AMS 7003 specifies powder requirements (chemistry, PSD, morphology), process controls (machine calibration, atmosphere purity, powder recycling limits), mandatory post-processing (stress relief, HIP per AMS 2774), and minimum mechanical properties (UTS 895 MPa, YS 825 MPa, elongation 10% for annealed Ti-6Al-4V). ### FAA Certification The FAA has approved AM parts for flight-critical applications through the existing 14 CFR Part 25 airworthiness framework. The approach requires the applicant to demonstrate an "equivalent level of safety" through extensive testing: - Material allowables development (A-basis and B-basis per MMPDS/CMH-17 methodology) from statistically significant test datasets (typically 30+ specimens per orientation per condition) - Process specifications locked and controlled under the applicant's quality system - Witness testing and recurring production testing to verify consistency GE Aviation's LEAP fuel nozzle (certified 2015) and GE9X combustor mixer (certified 2020) are production-volume examples of FAA-certified AM parts. ## Medical Device Standards ### ASTM F3001 (Ti-6Al-4V for Surgical Implants) F3001 specifies composition, microstructure, and mechanical properties for AM Ti-6Al-4V ELI (Extra Low Interstitials). Key requirements: - Oxygen: max 0.13 wt% (stricter than standard Grade 5) - UTS: min 860 MPa - Elongation: min 8% - Full density after HIP ### FDA Pathway The FDA's 2017 guidance document "Technical Considerations for Additive Manufactured Medical Devices" outlines expectations for device manufacturers: 1. **Device description**: AM process, material, post-processing, and design intent 2. **Process validation**: Demonstrate that the AM process consistently produces parts meeting specifications across the build volume 3. **Material characterization**: Composition, porosity, microstructure 4. **Mechanical testing**: Static, fatigue, and wear testing per appropriate ASTM standards 5. **Biocompatibility**: Per ISO 10993, tested on finished (post-processed) parts, not raw material 6. **Cleaning validation**: Residual powder removal from porous structures and internal channels Over 100 AM medical devices have received FDA clearance, predominantly orthopedic implants (acetabular cups, spinal cages, cranial plates) printed in Ti-6Al-4V and CoCrMo. ## Quality Management Systems ### AS9100 / ISO 9001 Aerospace AM suppliers must maintain AS9100 certification. Key AM-specific quality elements include: - **Machine qualification**: Installation qualification (IQ), operational qualification (OQ), and performance qualification (PQ) for each AM system - **Parameter lock**: Once a process is qualified, laser power, scan speed, layer thickness, and all other essential parameters are locked under change control. Any parameter change requires requalification. - **Powder management**: Incoming inspection, lot traceability, recycling records, and retirement criteria - **In-process monitoring**: Melt pool monitoring (cameras, photodiodes), layer imaging, and oxygen monitoring provide real-time quality data ### ISO/ASTM 52920 ISO/ASTM 52920 (2023) provides a framework for AM facility qualification, defining three levels of facility maturity corresponding to part criticality. It covers personnel qualification, equipment qualification, material control, and process control requirements. ## Testing Approaches ### Witness Specimens Small test specimens (tensile bars, fatigue specimens) are built alongside production parts on each build plate. These witness specimens verify that the build achieved acceptable material properties. Failure of witness specimens triggers investigation and potential rejection of the entire build. Placement matters: specimens at the edges and center of the build plate capture spatial variation in gas flow, temperature, and recoater effects. ### CT Scanning for Internal Quality Industrial computed tomography (CT) is increasingly used for 100% inspection of AM parts. CT detects internal porosity, lack-of-fusion defects, trapped powder in internal channels, and dimensional deviations from the CAD model. Resolution depends on part size; for typical AM components, voxel sizes of 10-50 micrometers detect defects relevant to fatigue life. CT does not replace mechanical testing but provides non-destructive verification that the internal structure is free of critical defects. ## The Path Forward The AM qualification landscape is maturing rapidly. Point-of-use qualification (qualifying a specific part made on a specific machine with specific parameters) is giving way to broader process qualification approaches where a validated process envelope allows part-to-part variation within proven bounds. Digital twins — physics-based simulations of the build process calibrated against real monitoring data — are emerging as tools to reduce the test burden by predicting quality from process data rather than destructive testing alone.