Additive Manufacturing Testing for Aerospace: Material Properties & Standards
Additive Manufacturing TestingWhy Testing Is Critical in Additive Manufacturing
Additive manufacturing (AM) — including selective laser melting (SLM), electron beam melting (EBM), directed energy deposition (DED), and binder jetting — builds parts layer by layer from digital models, enabling geometric complexity impossible with conventional subtractive methods. However, the layer-by-layer deposition process introduces unique microstructural features and defect types — including porosity, lack-of-fusion defects, anisotropic grain structures, residual stresses, and surface roughness — that make rigorous testing essential before parts enter service.
The aerospace, defense, medical implant, and automotive industries have led the adoption of AM for structural and functional components, and each industry imposes strict qualification requirements validated through comprehensive testing programs.
Unique Defect Types in Additive Manufacturing
Porosity
Gas porosity (spherical pores from trapped shielding gas) and lack-of-fusion porosity (irregular voids from insufficient energy input between layers or scan tracks) are the most common AM defects. Porosity reduces fatigue life more severely than equivalent defects in wrought material due to stress concentration at irregular void shapes. Computed tomography (CT scanning) per ASTM E1570 provides three-dimensional porosity mapping with sub-100 µm resolution.
Residual Stress
Steep thermal gradients during rapid melting and solidification generate large residual stresses — tensile at the surface in SLM-processed metals. Residual stresses reduce fatigue life, cause distortion during machining, and can trigger stress corrosion cracking. X-ray diffraction (XRD) and neutron diffraction measure residual stress depth profiles non-destructively per ASTM E915.
Anisotropic Microstructure
Columnar grain growth in the build direction produces anisotropic mechanical properties — often 10–20% lower tensile strength and significantly reduced fatigue life in the build direction vs. the transverse direction. Build direction-dependent tensile testing (ASTM E8, ASTM F2971) quantifies anisotropy to support design-allowable development.
AM Testing Methods and Standards
Mechanical Testing
Tensile, compressive, fatigue, fracture toughness, and hardness testing of machined coupons built from representative AM builds characterize mechanical properties as functions of build direction, heat treatment condition, and process parameters. ASTM F2971 (reporting data for AM specimens) and ASTM F3049 (powder characterization) define AM-specific requirements.
Non-Destructive Evaluation
CT scanning is the preferred NDE method for AM parts — it images internal geometry, detects porosity, verifies internal channels, and confirms dimensional accuracy simultaneously. Ultrasonic testing, radiography, and dye penetrant inspection supplement CT for production inspection of large or complex parts.
Powder Characterization
Feedstock powder quality directly determines the quality of AM parts. Powder particle size distribution (ASTM B822, laser diffraction), morphology (SEM), flowability (Hall flowmeter per ASTM B213), apparent density (ASTM B212), and chemical composition (ICP-OES, combustion analysis) are measured before each build campaign.
Conclusion
Therefore, testing is an essential aspect of additive manufacturing, especially given the defects arising from the layer-by-layer manufacturing process, which can lead to porosity, residual stress, and an anisotropic microstructure, thereby affecting the performance of manufactured products. Mechanical tests and powder characterization are crucial for ensuring products meet the necessary requirements, especially in the aerospace, medical, and automotive industries, per ASTM standards.
Why Choose Infinita Lab for Additive Manufacturing Testing?
Infinita Lab addresses the most frustrating pain points in AM testing: complexity, coordination, and confidentiality. Our platform is built for secure, simplified support — from CT scanning and powder characterization to full mechanical property development programs — fast, seamlessly, and behind the scenes.
Looking for a trusted partner to achieve your research goals? Schedule a meeting with us, send us a request, or call us at (888) 878-3090. [Request a Quote]
Frequently Asked Questions
What is the difference between gas porosity and lack-of-fusion defects in AM parts? Gas porosity forms as spherical pores when dissolved shielding gas is trapped during rapid solidification — relatively benign due to smooth geometry. Lack-of-fusion defects are irregular, crack-like voids forming when insufficient energy fails to melt and bond adjacent layers or scan tracks — far more damaging to fatigue life due to sharp stress concentrating geometry.
Which NDT method is best for detecting internal defects in metal AM parts? X-ray computed tomography (CT scanning) is the most capable method for metal AM parts — it detects internal porosity, measures pore size and distribution, verifies internal channel geometry, and provides full 3D defect mapping. It is used for both process development and qualification of flight-critical aerospace AM parts.
What standards govern mechanical testing of AM parts? ASTM F2971 (reporting data for additive manufactured specimens), ASTM F3122 (evaluating mechanical properties of metal AM materials), ASTM E8 (tensile testing), and ASTM E466 (fatigue testing) are the primary mechanical testing standards applied to metal AM parts.
How does heat treatment affect additive manufactured parts? Post-build heat treatment — including stress relief, hot isostatic pressing (HIP), solution annealing, and aging — reduces residual stress, closes pores (HIP), recrystallizes columnar grains to equiaxed microstructure, and develops precipitation-hardened microstructures. Most aerospace AM qualification programs require HIP for fatigue-critical applications.
What powder properties are most critical for metal AM quality? Particle size distribution (PSD), morphology (spherical, satellite-free), flowability, apparent density, and chemical composition (especially O, N, H content) are the critical powder parameters. Inconsistent powder leads to variable packing density and energy absorption, causing porosity and microstructural variation in AM builds.
