Study of HVOF parameters influence on microstructure and wear resistance of Cr3C2 - 25NiCr coatings

Cavitation wear is usually a serious problem to turbines, since it can influence blades profile. The wear affects efficiency and work availability of hydroelectric turbines, mainly in environments with high density of sand. One way to improve wear resistance is by thermally sprayed deposition coatings. This paper presents the analysis of microstructure, cavitation and erosion resistance on samples deposited with different HVOF parameters. HVOF deposition parameters as oxygen flow rate, C3H8 flow rate and their ratio are the focus of this paper. The main objective is to find the best combination of HVOF flame parameters on Cr3C2 – 25NiCr coating properties. In addition to the analysis of wear resistance, the article will also analyse coatings properties, such as microhardness and porosity level. Six coating samples were prepared; the sample with the highest oxygen flow rate and the lowest fuel/oxygen ratio, presented the lowest porosity level and the highest microhardness. Those results are even better than HVOF parameters recommended from manufacturer.