Microstructure characteristics of NiCrBSi/WC coatings on medium-Ni-Cr infinite chilled cast iron by laser cladding

Thick composite coatings of tungsten carbides (WC) in a metal matrix are ideal for components subjected to heavy abrasive wear. Laser cladding NiCrBSi/WC composite layers were produced on medium-Ni-Cr infinite chilled cast iron substrates with a continuous wave (CW) CO3 laser using the powder delivering technique. Different substrate temperature was selected during the cladding process. And the optimised preheat temperature was 300°C. Microhardness of the cladding layers was measured and the microstructure was characterised by optical microscope (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The chemical composition of the coating was analysed by the energy dispersive X-ray analysis (EDAX) equipped in the SEM machine. The results show that over 0.5 mm thickness, fully dense and crack-free cladding layers of NiCrBSi/WC can be formed on medium-Ni-Cr infinite chilled cast iron substrate. Average microhardness values of the metal matrix composite coating is as high as 900 HV, while the substrate is only 500 HV. The pin-on-plate wear tests showed the wear resistance of the cladding layer is substantially higher than that of the untreated substrate.