Wear mechanisms of epoxy-based composite coatings submitted to cavitation

Many hydraulic components are exposed to severe conditions such as high speed slurry and cavitation erosion, where the mechanical properties of the material in which they are manufactured, as well as the hydrodynamic profile of the components are crucial factors. These conditions are responsible for high maintenance and stoppage costs and seriously affect the reliability of power generation. In this work, coatings based on epoxy resins were applied onto stainless and plain carbon steel plates and their suitability to protect against cavitation erosion was evaluated. The cavitation erosion resistance was measured according to ASTM G32 standard in an ultrasonic cavitometer with an indirect-type sample positioning setup. The analysis of the microstructure and the worn surfaces of the samples showed that pores, matrix–reinforcement interfaces and cracks acted as nucleation sites for cavitation. The coatings presented good cavitation resistance based on incubation time measurements, but those that lasted longer showed 2 acceleration periods instead of the ordinary S-shaped time-variation curve typical of many metallic materials, which was mainly attributed to adhesion problems.