Study on the performance of laser cladding Ni-based WC60 composite coatings

Nickel-based Tungsten Carbide (WC) materials have excellent wear resistance and high temperature stability. They are prone to cracking during laser cladding due to the rapid cooling and heating characteristics. The sensitivity of cracking differs when cladding different substrates, which is a bottleneck for the industry. Quantitatively revealing the laser cladding mechanism of nickel-based WC is significant for optimizing the process. In this paper, a coupling model of the thermal field, flow field, and stress field was established for the laser cladding of nickel-based WC60 on a 42CrMo substrate. The model considered the influence of the powder absorption, surface tension and buoyancy on the flow for liquid metal and focused on analyzing the transient evolution during laser cladding. Cladding samples were prepared and subjected to the X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS), and microhardness characterization experiments. The morphology and mechanical properties of WC60 based on nickel were observed, and its solidification characteristics were analyzed. The calculations show that the maximum temperature during laser cladding reaches 2529 K, forming an upward Marangoni flow with a maximum velocity of 0.25 m/s. The thermal stress of the cladding layer reaches 616 MPa, and the residual stress reaches 647 MPa. The experiments show that WC particles are spherical and exist in the cladding layer as hard phases, deposited in the middle and lower parts of the cladding layer, which effectively enhances the hardness of cladding layer. WC particles impede columnar crystal growth, and some WC particle boundaries undergo melting, leading to the diffusion of tungsten elements into the cladding layer. This study provides a theoretical basis for optimizing the laser cladding process of nickel-based WC and improving the coating performance.