Laser additive manufacturing of CrFeNb particles reinforced Ni-based superalloy composites with grain refinement and superior performance

Laser power bed fusion (LPBF) as a widely used laser additive manufacturing, which has demonstrated a promising capability in the simultaneous formation of high-performance composites with unique microstructure. In order to further meet the urgent needs of aerospace sophisticated equipment, this work investigated the laser additive manufacturing of CrFeNb particles reinforced Ni-based superalloy composites with grain refinement and superior performance. A few CrFeNb particles were added to IN718 superalloy powder. The CrFeNb particles as a center of heterogeneous nucleation effectively facilitated to produce fine equiaxed grains and did not introduce significant residual stress in the as-deposited IN718 with CrFeNb composites. The stress concentration of the heat-treated IN718 with 4 wt% CrFeNb composites was significantly reduced. The grain orientation was not along the <001> and tended towards random. The particle size of as-deposited IN718 with 4 wt% CrFeNb composites was refined and the average size was 13.46 μm. The unmelted CrFeNb particles were dissolved and diffused into the γ matrix during heat treatment. A hard brittle phase was rich in Nb and Mo elements along the grain boundary. Under the combined effect of three strengthening mechanisms, the mechanical properties of the IN718 with 4 wt% CrFeNb composites at room temperature were improved. The yield strength, tensile strength and microhardness of the heat-treated IN718 with 4 wt% CrFeNb composites reached to 1194 MPa, 1426 MPa and 521 HV, respectively. This study provides a new method and foundation for the preparation and application of IN718 composites with excellent performance.