Study on crack behavior of laser cladding ceramic-metal composite coating with high content of WC

The purpose of this work is to investigate the cracking behavior and crack formation mechanism of high WC wt% composite coatings. Three NiCrSiBC-WC composite coatings with respective WC wt% of 40%, 50%, 60% were prepared on carbon steel substrates by laser. The macro- and micro-morphologies together with phase compositions of three coatings were comparatively observed. Further, the hardness, residual stress and toughness values of three coatings were tested and calculated quantitatively to get a clear understanding of crack formation. As a result, cracks occurred in 50% and 60%WC coatings but not being found in 40%WC coating. With increasing WC wt%, grains were more refined while more cracks occurred. The cracking of 50%WC coating was attributed to high tensile residual stress coupled with low toughness. Whereas compared with 50%WC coating, the higher crack susceptibility of 60%WC coating was mainly because of further increased residual stress.