Speaker
Description
Layer-wise addition of metal to directly form components or add coatings via laser powder bed fusion (LPBF) or laser directed energy deposition (DED) can generate very high levels of residual stress which affect component durability if not adequately addressed. These techniques also result in novel, non-equilibrium microstructures, sometimes with desirable features, that interact with traditional residual stress relief and microstructure manipulation heat treatments.
In LPBF nickel superalloy 718, neutron diffraction was used to demonstrate that a complex residual stress state can persist through a non-recrystallising heat treatment at 960 ºC plus subsequent ageing. The same treatment has been previously shown to relieve residual stresses and promote grain growth in conventionally manufactured material. This discrepancy is attributed to the presence of nano-scale intercellular precipitates and a large concentration of existing dislocations, both consequences of the LPBF process, which act to impede recrystallisation and creep processes. The residual stress state is shown to influence the long-crack fatigue threshold at low stress ratios. Higher temperature annealing successfully relieved residual stresses but resulted in recrystallisation and grain growth which reduced the yield stress.
To further explore residual stress and phase evolution during additive manufacturing, an in-beamline laser DED capability is being developed at ANSTO for both neutron and synchrotron use.
| Presenter Gender | Man |
|---|---|
| Pronouns | He/Him |
| Level of Expertise | Early Career <5 Years |
| Which facility did you use for your research | Australian Centre for Neutron Scattering |
| Condition of submission | Yes |
