Effect of W dissolution in NiCrBSi–WC and NiBSi–WC arc sprayed coatings on wear behaviors

Abstract

This work concerns the arc-sprayed NiCrBSi–WC and NiBSi–WC coatings produced from cored-wires. Porosity and WC/W2C contents were determined from the as-sprayed coatings. It was suggested that the dissolution of W into the Ni-rich matrix, which was more pronounced in NiBSi–WC coating and resulting in the thermal expansion coefficient of the matrix to reduce, caused this coating to have lower thermal stress from fabrication. This resulted in a lower amount of WC/W2C detachment in NiBSi–WC coating. The dissolution of W however has an adverse effect of reducing the WC/W2C contents in the coating, which reduces its hardness. Wear testing revealed that, even though the NiCrBSi–WC coating contained higher WC/W2C content than the NiBSi–WC coating due to lower W dissolution, its performance was inferior to the latter. In the dry sliding wear test, the problem of WC/W2C detachment on the contacting surface became exacerbated in the NiCrBSi–WC coating, leaving craters on the wear surface. In the three-body abrasive wear test, there was much less WC/W2C detachment. However the NiBSi–WC coating continued to out-perform the NiCrBSi–WC coating, suggesting that the higher W dissolution into the Ni-rich matrix has a major role in increasing the abrasive resistance of the coating.