Microstructure and interfacial metallurgical bonding of 1Cr17Ni2/carbon steel extreme high-speed laser cladding coating.

The extreme high-speed laser cladding (EHLA) was employed to fabricate a 1Cr17Ni2 coating. The solidification behavior, phase transformation, and interfacial metallurgical bonding of the coating were systematically investigated. The results showed that the major phase transformation during solidification was liquid to γ-Fe. The large temperature gradient of melting pool and slow grow rate of γ-Fe grain contributed to the fine columnar prior austenite grain (PAG) in coating. The largest thermal conductivity of [0 0 1] crystal direction determined the preferential [0 0 1] orientation of PAG perpendicular to the liquid-solid interface. A thin γ-Fe layer (approximately 5 μm) was observed between coating and substrate. The Bain relationship between interfacial γ-Fe layer and substrate and the K-S relationship between interfacial γ-Fe layer and coating contributed to the reliable metallurgical bonding between coating and substrate. The shear test revealed the high shear strength (approximately 92% of that of substrate) and weaker plastic deformation ability of the interface. The interfacial γ-Fe layer effectively combined the coating and substrate via K-S and Bain crystallographic relationship.