Erosion-Corrosion Simulation of Thermally Sprayed WC-Based Cermet in Artificial Seawater and Dam Water Environments
Keywords:coating, HVOF, erosion-corrosion, potentiodynamic, hydro-turbine
Mechanical equipment operated in a water dam environment is at risk of erosion-corrosion. To address this issue, thermally sprayed cermet coatings are an adequate solution for increasing resistance to corrosion and wear in hydro turbines, especially with high river sedimentation loads such as those in Cirata and Jatiluhur dams in Indonesia. In this study, WC-based cermet coatings with WC-10Co-4Cr and WC-12Co respectively were coated on AISI 1030 steel substrate and evaluated in media simulating the Cirata and Jatiluhur water dam environments, as well as in simulated seawater conditions. The morphology and structure of the sprayed coating were analyzed by SEM and XRD, and microhardness, porosity, and surface roughness were also studied. The corrosion resistance of the coating was evaluated using potentiodynamic polarization. More importantly, erosion-corrosion resistance in seawater simulations studied by Closed Flow Loop System (CFLS) equipment utilizing coupon tests was also explored. The results showed that the WC-10Co-4Cr coating has good electrochemical corrosion resistance with less erosion-corrosion compared to the WC-12Co coating, at 0.06-0.15 mm/year and 0.16-0.26 mm/year, respectively. Coatings with Cr content show a lower corrosion rate due to the formation of stable WCr2O6 and W18O49 oxides, making them a good choice for coating hydro turbine components.
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