Powder and additive
Metal additive manufacturing: what goes wrong and where to inspect
Laser powder bed fusion builds complex metal parts layer by layer: tooling inserts, aerospace brackets, medical implants and spare parts.
01How the process works
A laser melts thin layers of metal powder according to the CAD slice, repeating thousands of times. Parts are stress relieved, removed from the build plate, often HIP treated and machined. Directed energy deposition adds material with a powder or wire fed head.
Quality depends on powder condition, machine qualification, parameter set and build orientation. Porosity, lack of fusion and residual stress are the main risks; witness coupons in each build and CT scanning verify the result.
- Powder control. Powder lot, reuse and sieving.
- Build preparation. Orientation, supports, parameters.
- Building. Layer by layer laser melting.
- Post processing. Stress relief, removal, HIP, machining.
- Testing. Coupons, CT, dimensions.
02What typically goes wrong
| Defect | Typical cause | How it is found |
|---|---|---|
| Lack of fusion porosity | Parameters, powder | CT scan, metallography |
| Gas porosity | Powder moisture | CT |
| Distortion and cracks | Residual stress, supports | CMM, visual |
| Surface roughness | Orientation, down skins | Roughness tester |
| Low properties | Heat treatment, contamination | Coupon tests |
| Powder contamination | Reuse control | Chemical analysis |
03Where an inspector should look
Before production
- Machine and parameter qualification
- Powder specification and reuse limits
During production
- Build logs and monitoring
- Witness coupons
After production
- CT or density check
- Coupon tests
- Dimensions after machining
04Standards and references
ISO/ASTM 52900 series, ISO/ASTM 52920 (qualification), ASTM F3301 (post processing).
Standards are named for orientation. The applicable edition and acceptance criteria are those in your contract and specification.