Cavitation erosion frequently occurs in hydraulic equipments like: hydraulic turbines, valves, pumps and ship propellers. Arc Thermal Spray Process has a possibility to recover hydraulic blade runners in short maintenance period. Fe-Cr-Mn-Si is a cavitation resistance class of steel with high oxidation elements concentration, which can be important for arc thermally sprayed coatings. Fe-Mn-Cr-Si is a class of steel with strain induced phase transformation. Chemical composition influence on oxide formation, microstructure and cavitation resistance of Fe- Mn-Cr-Si thermally sprayed coatings were studied as well as field performance evaluation in Francis type runner. Microstructures and properties were investigated by XPS, XRD, optical microscopy and ultrasonic cavitation test. The best cavitation resistance was obtained in Fe-Mn-Cr-Si alloy with Ni addition because their lower oxide and splash droplets content and better splats wetting than Fe-Mn-Cr-Si without Ni. Strain induced phase transformation occurred in arc thermally sprayed coatings during cavitation tests. Better performances for Fe-Mn-Cr-Si alloys, without Ni, were obtained in alloys with higher strain induced martensite contents after cavitation tests. In field tests, after 2.000 operation hours, it was verified that the recovered areas presented only a small amount of eroded areas, with cavitation erosion reduction compared with uncoated areas.
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