Microstructure and Cavitation Erosion Performance of Cold-Sprayed WC-12Co and WC-17Co Coatings on Hydraulic Turbine Steels

Abstract

Hydraulic turbine steels experience severe wear and tear due to cavitation erosion (CE), impacting their efficiency and lifespan. This study investigates the microstructure and cavitation erosion performance of cold-sprayed tungsten carbide (WC) coatings on hydraulic turbine steel (CA6NM). Two coatings, namely WC-12Co and WC-17Co, were cold sprayed on turbine steel (CA6NM) by using a cold spray process. Then the microstructure analysis of the deposited coatings was done using SEM and XRD. Further, the cavitation erosion performance was examined using an ultrasonic vibration tester. The results indicate that WC decarburization did not occur. The microstructured WC-Co coating exhibits the lowest porosity and dense microstructure. Additionally, it was shown that the WC-Co coating has the greatest cavitation erosion resistance and it reduces the cavitation erosion rate by about one-third when compared to bare steel. In addition, higher jet velocity, normal impingement angle, and moderate stand-off distance were determined to be the dominant cavitation erosion variables that produced the maximum cavitation erosion. Among both coatings, WC-17Co coatings possessed higher hardness and microcrack resistance compared to WC-12Co. This may be due to their higher hardness and denser microstructure of WC-17Co coating than WC-12Co coating. Thus, this study demonstrates the potential of cold-sprayed WC-based coatings for protecting hydraulic turbine steels against cavitation erosion.