Research on the Mechanical Properties and Residual Stress of HVOF Sprayed Nanostructured WC-17Co Coatings

Abstract

Nanostructured WC-17Co coatings, nanostructured WC-12Co coatings, conventional WC-17Co coatings were prepared by means of High Velocity Oxygen Flame (HVOF) technique. The characteristic of powders and coatings of nanostructured WC-17Co coatings, hardness of different coatings, distribution gradient of the hardness of the nanostructured WC-17Co coatings in the depth direction, fracture toughness and interface fracture toughness of different coatings, residual stress of different coatings, different phase and distribution of WC phase in the depth direction were investigated. The results indicated that the micro-crack is spread along the phase interface where the brittle phase are more in the Co rich area , where there are more different properties in the Co rich area and W rich area, where there are more defects close to the intend end in the W rich area, even spread through the WC particles in microcosmic and the different residual stress of different phase are because of different melting point and different expansion coefficient , so the WC, W2C produced compressed stress, the Co6W6C produced tensile stress. The residual stress manifested from higher to lower in the depth direction of the coatings.