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

摘要

Cavitation wear is usually a serious problem to turbines, especially in water with abrasive content, 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. The main objective is to study erosion and cavitation wear resistance of Cr_3C2 - 25NiCr coating within different combination of HVOF flame parameters. HVOF deposition parameters as oxygen flow rate, C_3H_8 flow rate and their ratio are the focus of this paper. 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. In addition, samples with the highest surface hardness presented better erosion and cavitation wear resistance, and the erosion test conducted with an impingement angle of 60° presented more intense erosive wear.