When to pick DED over L-PBF for IN718
DED-LP blows powder through a coaxial laser nozzle onto a substrate. Build rates reach 100–500 cm³/hr (vs L-PBF's 10–35), envelopes can exceed 1 m, and the same head can repair worn surfaces by depositing onto existing parts.
Pick DED when the part is large, when you're cladding or repairing a high-value substrate, or when the part is geometrically simple enough that L-PBF resolution is wasted.
- Repair of turbine blade tips and shrouds
- Large monolithic parts (> 500 mm)
- Cladding of low-cost substrate with IN718
- Functionally graded parts (alloy transitions on the fly)
Defects and post-processing
DED IN718 has higher porosity (0.5–1.5 %) and coarser microstructure than L-PBF. Mandatory HIP + solution + age recovers most of the gap, with finished allowables ~5–10 % below the L-PBF baseline.
Surface finish is rough (Ra 25–60 µm); machine all critical surfaces.
Suggested parameters
Starting recipe on a 1 kW fiber laser DED head.
- Laser power: 800–1200 W
- Powder feed rate: 8–15 g/min
- Travel speed: 800–1500 mm/min
- Track overlap: 30–40 %
- Shield gas: argon
Frequently asked questions
Can DED achieve L-PBF properties?
Close to. After HIP + age, DED IN718 lands ~5–10% below L-PBF on UTS and ~15% on fatigue. For static-load parts the gap is irrelevant; for fatigue-critical parts use L-PBF.
Is DED actually used for repair in production?
Yes — turbine OEMs (GE, Pratt) qualify DED for blade-tip and shroud repair. The repair has a documented life equivalent to ~80% of a new part.
Sources
- ASTM F3413 — AM Directed Energy Deposition
- ASTM F3055 — AM Nickel Alloy (UNS N07718)
- AMS 5663