The cavitation erosion resistance of an X5CrNi18-10 stainless steel, solution treated at temperatures in the range of 1000–1100 °C for 5–50 mins, was investigated using a piezoceramic vibrating system. The variation of the technological parameters led to changes in the degree of the chemical homogeneity and the grain size of the austenite. Heating at 1050 °C for 25 mins, followed by water quenching, led to an increase in the cavitation erosion resistance of about 2.45 times compared to the samples heated for 50 mins. A significant improvement of the cavitation resistance was obtained for the sample maintained at 1050 °C compared to the samples annealed at 1000 and 1100 °C. It was found that the associated cavitation erosion resistance is improved for finer granulation and for higher degree of chemical homogeneity of the austenite.

The recent development in enhancing the corrosion resistance of materials by covering with powdered layers open the way to use the procedure also for cavitation erosion protection, phenomenon always present in hydraulic machinery runners as well as ship propellers. The present research analyzes the behavior of four different types copper layers, deposited with high velocity flames, HVOF upon specimens realized from cast steel for general use 270-480 W (equivalent with OT500-3 used in Romania), to cavitation erosion in a Laboratory device. Even if the powder density and the layers thickness have close values, the behavior to cavitation erosion is different and depend primarily on the powder chemical composition and the microscopic structure.

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Ultrasonic cavitation erosion experiments were performed on Ti-6Al-4V alloys samples in annealed, nitrided and nitrided and subsequently heat treated state. The protective oxide layer formed as a result of annealing and heat treatment after nitriding is eliminated after less than 30 min cavitation time, while the nitride layer lasts up to 90 min cavitation time. Once the protective layer is removed, the cavitation process develops by grain boundary erosion, leading to the expulsion of grains from the surface. The gas nitrided Ti-6Al-4V alloy, forming a TixN surface layer, proved to be a better solution to improve the cavitation erosion resistance, compared to the annealed and nitrided and heat treated state, respectively. The analysis of the mean depth of erosion rate at 165 min cavitation time showed an improvement of the cavitation erosion resistance of the nitrided samples of up to 77% higher compared to the one of the annealed samples.

The cavitation erosion of ductile cast iron with ferrite-pearlite microstructure was analyzed based on ultrasonic experiments performed according to ASTM G32-2010 and the resistance was compared to the C45 steel with similar hardness. The microstructural observation of the surface for different exposure times to the ultrasonic cavitation reveals the fact that the process initiates at the nodular graphite-ferrite interface and is controlled by micro-galvanic activities and mechanical factors. The cavitation erosion resistance was evaluated based on the evolution of the mean depth erosion and the mean depth erosion rate as a function of the cavitation time. The cavitation erosion rate of the cast iron is up to 1.32 times higher than the one of the C 45 steel with similar hardness. This is explained by the occurrence of stress concentrators due to the expulsion of the graphite from the metallic matrix.