Process and effects of heat treatment on mechanical properties of Co-Cr alloy manufactured by selective laser melting

The selective laser melting (SLM) process of cobalt-chromium alloy and the effect of heat treatment on microstructure, mechanical properties were systematically studied. The orthogonal experiment was designed to optimize the process parameters by using EOS M290 SLM equipment. The microstructure, phase and mechanical properties were observed and tested by XRD, SEM, hardness tester and universal material testing machine. The results show that the optimum hatch distance is 0.08 mm, the scanning speed is 1110 mm/s, the laser power is 335W, the energy density is 4.8 J/mm2, the density is as high as 99.18%, and the optimum hatch angle is 67. The phase of Co-Cr alloy formed by SLM is mainly composed of (fcc) and a small amount of (hcp) phases, and the microstructure of the alloy consists of fine uniform cell crystal and columnar crystal. The hardness, tensile strength and elongation of the Co-Cr alloy formed by SLM are 41.0 HRC, 1032 MPa, 10%, and the main fracture is transgranular ductile fracture. After heat treatment, the phase transition will occur, the microstructure is mainly composed of phase and a small amount of phase, and produces a small amount of an enhanced phase M23C6(M=Cr, Mo, W); the hardness, tensile strength and elongation are increased by 6.1%, 35.9% and 17.6%, respectively; the main fracture is quasi-cleavage fracture.