Effect of Cr3C2 Content on Microstructure and Properties of Laser Cladding Layer of Ni3Al-Based Alloy

Using Ni3Al+Cr3C2 mixed powder with different Cr3C2 contents as raw materials, Ni3Al-based alloy laser cladding layer was prepared on 45 steel by laser cladding technique. The content and average size of in-situ-formed carbides with different Cr3C2 contents were calculated by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and friction and wear testing machine, and the effects of carbides on the microstructure, microhardness and wear resistance of Ni3Al-based alloy cladding layer were analyzed. The results indicate that the microstructure of the Ni3Al-based alloy laser cladding layer contains mainly Ni3Al matrix and in-situ-formed Cr7C3 carbides. With the increase in Cr3C2 content, the proportion of in-situ-formed carbides in cladding layer is increased from 6.8% to 32.3%, the average size is increased from 0.10 mu m to 0.78 mu m, and the microhardness (HV) of the cladding layer is increased from 4615.8 MPa to 5968.2 MPa. When the content of Cr3C2 is 35%, the carbides are dispersed as small particles, and uniform wear occurs in the process of friction and wear test, so the wear loss of cladding layer is as low as 0.19 mg, and the wear loss of the disk is relatively the lowest, about 1.23 mg. However, when the content of Cr3C2 is 45%, the carbide content reaches 32.3%, and the carbides are mainly large size particles. In the process of friction and wear test, the large carbides particles break off, which accelerates the wear of the grinding disk.