Subsurface behavior of ductile material by particle impacts and its influence on wear mechanism

Erosion is observed in many industrial situations such as pneumatic conveying pipelines, shot peening and sand blasting where interaction between particle and surface is expected. A number of particle impact parameters and material surface properties are involved in the erosion process. Extensive studies have been conducted to understand the effects of the process parameters on erosion; however, only limited studies can be found in the literature associated with material surface and subsurface properties. In order to get a better understanding of the material surface and subsurface behaviour due to particle impacts for different parameters, erosion tests were performed for different impact angles and different particle velocities using a micro-sandblaster. Angular silicon carbide (SiC) particles were impacted on two different ductile surfaces, mild steel and aluminium, with a constant particle flux. Wear mechanisms were studied in terms of particle kinetic energy. Subsequently, the worn surfaces and their cross-sections were observed using scanning electron microscope (SEM) to relate the subsurface damage characteristics to different impact conditions, and to wear mechanisms. Results showed that at a lower impact angle, material was removed through cutting mechanism, while at a higher angle; material removed through predominantly deformation process. Also, subsurface cracking and subsurface damage were observed up to a certain depth from the worn surface. It appears both the depth of subsurface cracking and subsurface damages increases with increasing impact velocity. The variation is consistent with increase in surface and subsurface temperature at higher velocities. With increased temperature, the depth of the heat affected zone increases, which increases the work hardening layer thickness. In addition, subsurface microstructural damage is consistent with attainment of higher temperature which can be explained through the high strain-rate deformation and thermo-physical properties of the surface.