Laser cladding of high Co-Ni secondary hardening steel on 18Cr2Ni4WA steel

Laser cladding of the high Co–Ni secondary hardening steel on the 18Cr2Ni4WA steel using the laser direct metal deposition (LDMD) technology was investigated. The hardness was measured with a Vickers indenter, and the microstructural evolution was analyzed using a SEM equipped with an EDS and X-ray diffraction. The results indicated that the wear resistance of the 18Cr2Ni4WA steel substrate could be greatly improved by the coating of laser cladded high Co–Ni secondary hardening steel. After laser cladding, the microstructure of the heat-affected zone in the 18Cr2Ni4WA steel substrate was typical martensitic structure transformed from the initial granular bainitic structure. Besides, Fe-based ferrite, martensite, lath retained austenite, and two types of precipitations dispersed in the matrix were observed in the laser cladded high Co–Ni secondary hardening steel coating. They were determined to be the needle-shaped Fe(Cr, Co, Ni)3C cementite with size of approximately 1–3μm and rod-shaped fine-scale (less than 0.1μm in length) M2C carbides, respectively.