Microstructure and Mechanical Properties of 17-4 PH Stainless Steel Gas- and Water-Atomized Powders Processed by Laser Powder Bed Fusion (L-PBF)

摘要

In this paper, parts fabricated by the laser powder bed fusion (L-PBF) of 17-4 PH stainless steel gas and water atomized powders were examined for density, phase evolution, microstructure and mechanical properties as a function of laser power and scan speed, expressed by the energy density parameter. For all energy densities, the gas-atomized L-PBF parts appeared to consist solely of martensite phases, whereas the water-atomized L-PBF parts appeared to consist of a mixture of austenite and martensite phases, based on X-ray diffraction (XRD) analysis. At a low energy density of 64 J/mm~3, low-porosity and high-density (～97% density) L-PBF parts were produced from gas-atomized (D_(50)=13μm) and water-atomized (D_(50)=17μm) powders but lower densities (～87-92%) were observed for the remaining two water-atomized powders (D_(50)=24μm and 43μm). However, at low energy densities, the ultimate tensile strengths (UTS) for all the water-atomized L-PBF parts ranged between 470-690 MPa while the gas-atomized L-PBF parts with UTS of 1000-1120 MPa. The comparable mechanical properties observed for water-atomized L-PBF parts at a high energy density of 104J/mm~3, can be attributed to the decrease in grain size and to the presences of both austenite and martensite phases in the microstructure.