Microstructure, Properties and Crack Suppression Mechanism of High-speed Steel Fabricated by Selective Laser Melting at Different Process Parameters

Abstract To enrich material types applied to additive manufacturing and enlarge application scope of additive manufacturing in conformal cooling tools, M2 high-speed steel specimens were fabricated by selective laser melting (SLM). Effects of SLM parameters on the microstructure and mechanical properties of M2 high-speed steel were investigated. The results showed that substrate temperature and energy density had significant influence on the densification process of materials and defects control. Models to evaluate the effect of substrate temperature and energy density on hardness were studied. The optimized process parameters, laser power, scan speed, scan distance, and substrate temperature, for fabricated M2 are 220 W, 960 mm/s, 0.06 mm, and 200 ℃, respectively. Based on this, the hardness and tensile strength reached 60 HRC and 1000 MPa, respectively. Interlaminar crack formation and suppression mechanism and the relationship between temperature gradient and thermal stress were illustrated. The inhibition effect of substrate temperature on the cracks generated by residual stresses was also explained. AM showed great application potential in the field of special conformal cooling cutting tool preparation.