Abstract
Recent studies have demonstrated that WC-12Co and WC- 10Co-4Cr coatings were the best performing HVOF coatings against erosion. This paper looks at the influences of the HVOF process parameters for WC-12Co and WC-10Co-4Cr materials on the erosion resistance of the coatings. The effect of powder morphology, matrix chemistry and HVOF process parameters with respect to both silica slurry erosion and alumina dry erosion has been studied. All coatings were produced using the HVOF JP-5000 system with kerosene-oxygen flame. The spraying parameters were analyzed in term of sprayed particle velocity and temperature as measured with the DFV2000 optical diagnostic system. Simultaneously with in-flight particle measurements, the substrate-coating temperature was monitored by infrared pyrometry during coating deposition. The resulting coating microstructure was evaluated in terms of microhardness, porosity type and extent of wear damage after dry and slurry erosion. The material volume loss under various erosion conditions was related to the coating properties and microstructure. According to the experimental results, the following conclusions are drawn: 1) the kerosene flow rate affects the inflight particle state (velocity and temperature) and the coating porosity. 2) Cobalt-chrome matrix cermet performs better in slurry erosion while denser and harder cobalt matrix cermet performs better in dry erosion. 3) The use of kerosene-rich flame with lower oxygen stoichiometry reduces the carbide degradation and optimizes the wear performance of WC-12Co coatings in both dry and slurry erosion.
