Laser powder bed fusion of CoCrNi composite with high fraction of TiC: The microstructure and mechanical properties at different temperatures

At present, high fraction nano-TiC containing CoCrNi-4wt%TiC composite has been obtained through laser powder bed fusion (LPBF) of the blends of elemental powders and nano-TiC particles. Due to the addition of high fraction nano-TiC particles, there is a significant improvement in the strength of the composite to 1886 MPa at 77K, 1456 MPa at 298K, 528 MPa at 1073K, 300 MPa at 1173K, respectively. Characterized by high scanning speed and high laser power, the laser scan strategy combining is effective in preventing the nano-TiC particles from agglomeration, and the nano-carbides show a heterogeneous distribution with a higher number density and a finer particle size at the bottom of melting pool, the mechanism of which is discussed. The second-phase strengthening of the high-density nano-carbides combining dislocation strengthening or grain boundary strengthening raises the yielding strength of the composite compared to CoCrNi alloy at cryogenic or elevating temperature, respectively. Combining with the deformation-induced nano stack faults/twins plasticity and heterogeneous distribution induced (HDI) strengthening, the addition of high-density nano-carbides contributes to the high tensile strength and good plasticity of the composite at the temperature in a wide range.