Development of Near Net Shaped Coatings for Reduced Postprocessing Costs in Valves

Abstract

Thermally sprayed WC/CoCr coatings are established in the valve industry for wear protection. However, conventional coatings have to be cost-intensive postprocessed. Therefore, the aim of this study is to develop near net shaped (nns) WC/CoCr coatings with a high wear resistance in order to avoid the expensive grinding postprocess. For the development of the nns coatings, a parameter study is used to investigate the influence of the stand-off distance and hydrogen volume flow rate in the HVAF process. The parameter study indicates the influence of the hydrogen volume flow and the stand-off distance on the porosity, microhardness and wear resistance of the coatings. The developed coatings exhibit a low porosity and high wear resistance. Through the correlation of the coating properties with the process parameters, promising parameter ranges for a further development of HVAF-sprayed nns coatings of WC/CoCr can be identified. With these results, first benchmarks for HVAF process parameters, hydrogen flow rate and stand-off distance could be delivered, advancing the overall goal of reducing manufacturing costs of valves.