Optimization of Preparation Process Parameters of Low Carbon WC-12Co Coatings and Study on Corrosion Resistance in Molten Zinc Bath

Abstract

To optimize the corrosion resistance in molten zinc of the surface coating of the galvanized sinking roll, the low carbon WC-12Co coatings were prepared on 316L stainless steel substratre using supersonic flame spraying technology, and a kind of four factors and three levels (L9 (34)) orthogonal experiment was designed to optimize the spraying process. Subsequently, the phase structure, microstructure, porosity, bonding strength and resistance to molten zinc corrosion of low carbon WC-12Co coatings were evaluated. Results showed that the change of spraying process parameters had little effect on the phase composition of the coatings, but had a significant effect on their porosities. The influence of various factors in the spraying process parameters on the porosity of the coating was arranged in descending order: kerosene flow rate >spraying distance >powder feeding rate >oxygen flow rate. Moreover, the spraying process parameters that could obtain the lowest porosity WC-12Co coating were the kerosene flow of 26.5 L/h, the oxygen flow of 55.2 m3/h, the powder feeding rate of 60 g/min, and the spraying distance of 326 mm. The high-density low carbon WC-12Co coating with high compact microstructure prepared under these parameters could effectively isolate the molten zinc, which was suitable for the surface protection of galvanized sink rolls.

Keywords

• supersonic flame spraying|low carbon wc-12co coating|process parameters|porosity|sink roll|resistance in molten zinc corrosion