Effect of Post-Heat Treatment on Clad Layer of High-Speed Tool Steel Fabricated by Laser Direct Metal Deposition
摘要
Laser direct metal deposition (L-DMD) was employed to fabricate high-speed AISI M2 tool steel deposits as a promising material for tribological enhancement and to refurbish critical and high-performance components. This study provides critical insights into the microstructure–property relationships of L-DMD-fabricated M2 tool steel and demonstrates M2 clad layer response for tempering cycles to achieve the segregations and dendritic network free microstructure with fine secondary carbide distribution in tempered martensitic laths. The microstructural characteristics are correlated with achieved hardness and wear behavior. The as-deposited M2 tool steel microstructure featured austenite dendrites with martensite laths and an interdendritic segregation network. After two tempering cycles, the interdendritic network dissolved, and carbides (MC and M2C) precipitated. X-ray diffraction (XRD) analysis revealed a decrease in dislocation density from 3.8 × 1014 m−2 (as-deposited) to 2.4 × 1014 m−2 after tempering. Hardness increased from 685 to 740 HV after one tempering cycle but decreased to 690 HV after the second cycle due to martensite softening. Fretting wear rates increased from 1.2 × 10−6 mm3/Nm (as-deposited) to 3.5 × 10−6 mm3/Nm after two tempering cycles. These results demonstrate how post-clad tempering influences the microstructure–property relationship, providing performance insights of L-DMD M2 tool steel deposits.