Effect of heat input on the microstructure and mechanical properties of the deposition obtained by selective laser melting (SLM) of precipitation hardened martensitic stainless steel

The additive manufacturing (AM) shows a great market prospect in the closed-impeller for the centrifugal compressor. In the paper, the precipitation hardened martensitic stainless steel (PHMSS) deposition with different heat input parameters by the selective laser melting (SLM) and the micro-Vickers hardness, tensile strength and impact toughness were detected respectively. The evolution laws of microstructure were analyzed by the SEM, TEM, EDS and EBSD. The tensile strength of the deposition with heat input of the 4.21 J/cm were best and the strength along the build surface direction (X and Y) and the build height direction (Z) were 1193.3 MPa、1222.1 MPa、1159.8 MPa respectively. The impact toughness of the deposition were lower than that of base metas and the tonghness between the sureface direction and the bulid heght direction was anisotropy. The crystals showed a conlumanr pattern along the Z direction and with the increase the heat input, the preferred orientation along the Z changed from the preferred crystal plane and crystal orientation to the pure preferred crystal orientation. A large amount of Cr3C2 phase is precipitated and its size increased with the increase of heat input. The above research results normalize the influence of each parameter during the AM on the microstructure and mechanical properties of the deposition to the heat input, which is helpful to simplify the optimization of the procedure specification and promote its industrial application.