Study on Simulated Oxidation of WC Coating and its Effect on Aging Performance

The WC-17Co coating sprayed on the surface of key parts of a set of large domestic equipment becomes blue and purple locally when placed in the plant for a period of time. To study the reason for that and evaluate its impact on the coating service performance, a batch of WC-17Co coating samples are prepared. An environmental test box is used to adjust humidity and temperature to simulate the field environment for accelerated oxidation tests and in-situ observation. The adhesion, wear-resistance, and corrosion resistance are tested by pull-out method, reciprocating friction method, and electrochemical measurements. It is found that the WC-17Co coating prepared with the same parameters successfully reproduced the field corrosion appearance under the simulated conditions. By comparing the properties of WC-17Co coating before and after the corrosion, it is found that the adhesion strengths of the coating before and after the corrosion are higher than 60 MPa. The wear volume of the coating before and after the corrosion changes little. The corrosion only occurs on the surface of the coating, and the interior of the coating and substrate are not damaged. It can be concluded that the surface discoloration of the coating is due to the high temperature and humidity of the local summer environment, resulting in Co oxidation of the coating surface. The adhesion and wear-resistance of the oxidized coating are not significantly reduced. Therefore, the surface oxidation of the field coating will not affect its service performance.