Abstract
Improving the wear resistance and corrosion resistance of high-speed steel (HSS), WC/diamond/Co-based gradient composite coatings were produced on HSS substrates by laser cladding with different compositions powder mixture (Co-Cr alloy powder, 80Co-Cr alloy powder+20WC, 53Co-Cr alloy powder+40WC+7diamond, wt.%). The macromorphology, microstructures and phase composition were characterized by optical microscope (OM), scanning electron microscopy (SEM) equipped with energy dispersion spectrometry (EDS), and X-ray diffraction (XRD) techniques. The microhardness, wear resistance and corrosion resistance of the gradient coatings were also investigated respectively. The results indicate that the prepared WC/diamond/Co-based gradient composite cladding layer has a fine morphology on the cross sections and a gradient transition of the grain size has been achieved. The microhardness result presents gradient distribution along the depth of the coating. The microhardness is strengthened due to the dispersions of M7C3 (M is Fe, Cr), Co3C, CrCo, Cr3C2, Fe3C in the composite coating, and the highest microhardness of 1342 HV0.2 can be detected in the cladding layer. The friction coefficient values of the coatings range from 0.27 to 0.40, which is much lower than that of the substrate (0.50-0.60). Furthermore, the wear loss of coatings decreases by more than 3 times comparing with that of the substrate (3.5 mg). The polarization resistance results show that the cladding layer has excellent corrosion resistance with polarization resistance can reach the value of 236488.1 Ω·cm2. The gradient transition of the mechanical properties and chemical metallurgical combination between particle (WC, diamond) and adhesive phase can be obtained in laser cladding, which improves the wear resistance and corrosion resistance of the HSS surface.
Improve wear resistance of composite coatings on cutting tool from high-speed steel
