Microstructure and Properties of Metal-Ceramic Composite Coating by Laser Surface Alloying on 9CrSi Steel

Using sub-micron WC/Co metal ceramic composite as coating materials for laser alloying experiments to prepare high hardness and wear resistance alloyed layer on the surface of 9CrSi. The microstructures of laser-alloyed coating were detected by SEM and XRD. The microhardness and wear-resistance of the coatings were also investigated. The results indicate that, the laser alloyed layer and substrate form a good metallurgical bonding. The analysis of SEM reveal that the alloyed layer can be divided into alloyed zone, heat affected zone and substrate zone. The alloyed zone is composed by martensite, netted dendrite carbides and small carbide particles, the netted dendrite carbides distribute in the martensitic and the small carbide particles dispersed in the gap of the netted dendrite. The heat affected zone is consisted of retained austenite and martensite. There is no significant change in the matrix zone. The coating has a high hardness of 900H V(0.2), and the abrasion loss of the alloyed coating is just one ninth of that of 9CrSi. The wear resisitance of the alloyed coating relative to the substrate 9CrSi has significantly improved.