Study of the effect of abrasive flow machinig on the structure of the surface layer of the ceramic Al2O3 coating of the inner cylindrical surface

The article contains the results of a study of the influence of abrasive flow machining on the structure of the surface layer of the Al2O3 ceramic coating of the inner cylindrical surface. The experience of finishing the surface of ceramic coatings by grinding, hydro abrasive machining and abrasive flow machining is considered. Taking into account the high hardness of the aluminum oxide coating, black silicon carbide was used as a filler for the medium. The abrasive flow machining was carried out in seven stages. Each stage included 50 cycles of reciprocating flow of the medium through the machining channel. After each stage, a qualitative assessment of the coating surface structure was carried out with recording of a visual image of the surface on a microscope. A quantitative assessment of the change in structure was carried out by measuring the surface roughness. As a result of abrasive flow machining, it was possible to reduce the roughness of the surface layer from Ra = 16.9–18.5 μm to Ra = 3.6–3.68 μm. It is assumed that during machining, due to the removal of most of the microprotrusion peaks and smoothing of the surface layer, the contact area of the surface – the grain of the medium becomes significantly smaller. This leads to a significant decrease in the cutting depth and the transition of the machining mode from brittle to plastic. Based on the dynamics of change and structure of the surface layer of the ceramic coating, for complete removal of the original structure of the surface layer, 100–150 additional machining cycles will be required after 400 main cycles. The obtained results confirm the practical possibility of using this type of machining to improve the structure of the ceramic coating.