EFFECT OF Mo CONTENT ON MICROSTRUCTURE AND PROPERTIES OF LASER CLADDING Fe-BASED ALLOY COATINGS

Mo alloying Fe-based coating was fabricated on the surface of Q235 steel by using 6 kW fiber laser. The effects of Mo additions on the microstructure, microhardness and wear resistance of the cladding layer were studied by means of optical microscopy (OM), scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS), Vickers hardness tester and M-200 ring block wear tester. Research results showed that the microstructure of Mo-free cladding layer mainly consisted of matrix and eutectic structure. The matrix was martensite and retained austenite. The eutectic structure mainly consisted of M-2(B,C) and M-7(C,B)(3) type of eutectic borocarbides. With the increase of Mo content, there was no significant change in the matrix. However, the eutectic structure was transformed from M-2(B,C)- and M-7(C,B)(3)-type borocarbides into M-2(B,C)-, M-7(C,B)(3)- and M-23(C,B)(6)-type borocarbides. When the content of Mo is 4.0 wt.%, the Mo2C-type carbide appear on the matrix, and parts of the borocarbide networks are broken. The change of microhardness of the cladding layer was not obvious with the increase of Mo content. But the increase of Mo content increases the wear resistance of the cladding layer. The wear resistance of cladding layer with 4.0 wt.% Mo is 2.4 times as much as the cladding layer which is Mo-free.