Study on performance of laser cladding of 60 wt.%WC-Ni coating with ultrasonic/temperature composite energy field

Abstract

In order to suppress the crack and porosity sensitivity of the traditional laser cladding Ni-based WC coating, 60 wt.% WC-Ni coating was prepared on the 45 steel substrate by traditional, single temperature field assisted, and "ultrasonic vibration + temperature field" (UVAT) composite energy field assisted laser cladding. Scanning electron microscopy (SEM) and Electron Backscattered Diffraction (EBSD) were used to analyze the microstructure of the coating, and X-ray diffractometer (XRD) was used to analyze the phase of the coating. The mechanical properties, tribological properties, and electrochemical corrosion properties of the coating under different working conditions were compared and studied. The results show that there are a few cracks and pores in the coatings prepared by traditional and single-temperature field-assisted laser cladding, and WC particles are locally enriched. The vibration, agitation, and cavitation of UVAT can change the distribution state of WC particles and the binding state with the matrix phase so that the grain of the coating is fine, with no cracks, uniform and dense. The average microhardness of UVAT compound field-assisted laser cladding coating is 894.9 HV0.3, which is 1.23 and 1.14 times that of the first two processes, respectively. The wear rate is 51.62% and 12.68% of the first two, respectively, showing the best wear resistance. The wear mechanism of the three coatings is mainly abrasive wear, and the adhesive wear and oxidation wear are auxiliary. In 3.5 wt.% NaCl solution, the corrosion mechanism of the three coatings is intergranular corrosion, but the grain refining of the UVAT composite energy field coating leads to the increase of grain boundary density on the surface of the coating, the increase of corrosion channels, the reduction of corrosion tendency, and the enhancement of corrosion resistance. A new technical scheme is provided for the Ni-based WC coatings with no crack and high density.