Effect of higher layer thickness on laser powder bed fusion built single tracks of Ni-Cr-Fe-Nb-Mo alloy

Abstract

Laser Powder Bed Fusion (LPBF) is one of the revolutionary technologies that can fabricate complex-shaped components by selective melting of the pre-placed powder layer, using high-power laser as directed by the input digital files. Generally, research on the LPBF process is called out for layer thickness (LT) up to 50 µm and smaller beam diameter (≤100 µm), but it has lower productivity. In LPBF, higher productivity can be achieved with higher LT (>50 µm), but it consists of various process instabilities. In the present work, parametric studies are performed by laying Ni-Cr-Fe-Nb-Mo single tracks, using LPBF at higher LT. The process parameters such as laser power (P), scan speed (v), and LT are varied among 150–450 W, 0.04–0.1 m s⁻¹, and 80–160 µm, respectively, at three levels each. For the range of parameters under investigation, the maximum track width of 610 µm and aspect ratio of 7.63 are achieved at a P of 450 W and v of 0.04 m s⁻¹ at 80 µm LT. It is observed that an increase in the energy density and layer thickness resulted in the reduction of track width and aspect ratio due to material vaporization occurring from poor heat conductivity due to unconventionally high powder layer thickness. It is also observed that the build rate increases with an increase in P, v, and LT. As single tracks are basic building blocks, the obtained results can provide an insight into the effect of process parameters on LPBF-built single tracks at higher LT for building engineering components of required width with higher build rate. Furthermore, the track dilution is also found to increase with the increase in P and decrease in v.