Investigation of the microstructural evolution and mechanical properties of bimodal TiN-reinforced 316L stainless steel composite fabricated by SLM

Selective Laser Melting (SLM) preparation of TiN-reinforced 316L stainless steel effectively addresses the weaknesses of 316L stainless steel in terms of strength and hardness. While ensuring the flowability of the composite powder, this study employs dual-sized TiN particles to enhance 316L stainless steel. Experimental results indicate that micrometre-sized TiN particles are embedded in the matrix, and other TiN particles dissolve and re-form into cubic TiN particles with a diameter of around 200 nm. Samples produced at high laser energy density exhibit high density, consistently above 99%. The average grain size of the austenite is refined to 2.38 μm, and the tensile samples with a 90° interlayer rotation angle and island size of 60 × 10mm2 exhibit a maximum yield strength of 661 MPa, ultimate tensile strength of 950 MPa and elongation of 35.5%. Samples with lower laser energy density demonstrate the highest microhardness, reaching 365 HV. The corrosion resistance of samples with different scanning strategies is similar to pure 316L stainless steel, with the 67° interlayer rotation angle strategy showing the optimal corrosion resistance.