Microstructure Characteristic of Laser Cladding Ceramic Layer on High Cr Cast Steel Surface

Abstract

The Al2O3 gradient ceramics coating was cladded on the high Cr cast steel by 5KW crosscurrent CO2 laser with Ni-based alloy which was used as transition metal in this experiment. The microstructure is analyzed with optics microstructure analyzer and the crystal grain characteristic is studied. The results show that the microstructure of laser cladding layer contains the plane crystal zone which grows along the substrate, the cellular crystal zone, the dendritic crystal zone and the surface equiaxed cryatal zone. The microstructure of the coating compared with the substrate is extremely fine, and the microstructure of multi-layer cladding presents stratification. The phase composition of the cladding layer is composed primarily of NiAl intermetallic compound, also includes γ-FeNi and a little Ni3Al compound. The Al2O3 particles that some present the single crystal form and some accumulate in together, play the dispersion strengthening role in the coating material. The massive twin crystals and the dislocation pile-ups are found to exist in the cladding layer.