Effects of particle characteristics on the microstructure and mechanical properties of 17-4 PH stainless steel fabricated by laser-powder bed fusion

Abstract

The effects of powder characteristics (powder shape, size and type) and processing conditions (laser power and scanning speed) on the mechanical properties and microstructures of laser powder bed fusion (L-PBF) 17-4 PH stainless steel were studied using four types of powders. The % theoretical density, ultimate tensile strength, hardness of L-PBF parts are sensitive to energy density and starting powder shape, size and type. The density and mechanical properties of both water and gas-atomized powders increased with increased energy density. The gas-atomized (D-50 = 13 mu m) powders which are spherical in shape and water-atomized (D-50 = 17 mu m) powders of high tap density produced low-porosity and high-density (similar to 97% density) L-PBF parts at low energy densities of 64 and 80 J/mm(3). The increase in energy density to 104 J/mm(3) resulted in high dense (97 +/- 0.5%) water- and gas-atomized powders L-PBF parts. However, even at a high % theoretical density (97 +/- 1%), the properties of L-PBF parts varied over a relatively large range (UTS: 500-1100 MPa; hardness: 25-39 HRC; elongation: 10-25%). This large variation in mechanical properties could be attributed the martensite and austenite phase as well as grain size in the L-PBF parts. Furthermore, the martensite and austenite phase content and of the L-PBF parts were also sensitive to the energy density and starting powder type. (C) 2018 Elsevier B.V. All rights reserved.