Effect of heat treatment on the microstructure and mechanical properties of CX stainless steel fabricated by selective laser melting

Abstract A novel Corrax (CX) stainless steel was fabricated using the Selective Laser Melting (SLM) process. This study examined the influence of heat treatment processes on the microstructure and mechanical properties of CX stainless steel. Results indicate that SLM-fabricated CX samples mainly consist of martensite and residual austenite, with tensile strength and hardness of 1124 MPa and 337.4 HV, respectively. After solution treatment at 850 °C for 0.5 h (ST), the sample exhibited the highest martensite content, with nearly all residual austenite eliminated. Nickel and aluminum are fully dissolved within the matrix, leading to a supersaturated solid solution. This martensitic structure with a high dislocation density lays an important foundation for the subsequent aging treatment. Subsequent aging treatments at various temperatures demonstrate that when CX samples are subjected to solution aging at 850 °C for 0.5 h followed by aging at 525 °C for 4 h (ST + AT), all residual austenite is fully converted to martensite. The elements dissolved during the solution treatment precipitate, forming NiAl intermetallic compounds. This process leads to a substantial increase in tensile strength and surface hardness, achieving values of 1743 MPa and 526.8 HV, respectively. These results indicate that the solution and aging heat treatment significantly enhances the overall performance of CX samples.