Effect of hot isostatic pressing on the microstructures and mechanical properties of TiC/GTD222 composite fabricated by selective laser melting

In this work, hot isostatic pressing (HIP) treatment was performed on the TiC/GTD222 nickel-based composite prepared by selective laser melting (SLM). The effect of HIP on the microstructures and mechanical properties of the SLMed composite was investigated using XRD, SEM, EBSD and TEM. The results show that the microstructures of both SLMed and HIP-SLMed composites are composed of γ matrix, γ′ phase and carbides. The HIP treatment can significantly promote the formation of nanoscale carbides and γ′ phase, and simultaneously decrease the dislocation density of the composite. The yield strength and tensile strength of the HIP-SLMed composite increase by approximately 75 MPa and 189 MPa, respectively, while the elongation remains similar to that of the SLMed composite. The enhanced mechanical properties of the HIP-SLMed composite can be primarily attributed to the precipitation strengthening of the γ′ phase and the Orowan strengthening effect of the carbides. The microscopic deformation and strengthening mechanisms of the composites were also studied in detail.