Laser processing for increasing the durability of the piston rings

Abstract

Abstract. Problem. In the process of operation piston rings are subject to wear. Non-sufficient wear resistance of piston ring materials often limits the growth of productivity of machines and the timing of their operation. It is not always that the desired set of properties of piston rings made of cast iron can be achieved by traditional methods of thermal or chemical-thermal treatment. Thus, application of traditional boriding methods associated with diffusion of boron into the solid phase leads to formation of the working layer having high brittleness. Therefore, the actuality of the problem is to increase the wear resistance of piston rings without embrittlement. Use of laser heating at boriding provides the formation of a new layer with special properties. However, the optimum properties can only be achieved after establishing a relationship between the parameters of running a process and the depth of the borated layer. The goal was to determine the effect of laser heating parameters on the structure and depth of the borated layer, since the properties of piston rings depend on the depth of the latter. The studies conducted revealed that the increase in the speed of displacement of the part in the process of laser heating reduces the depth of the borated layer. Such a dependence is observed both at 0.15 mm thickness of coating and at a thickness of 0.30 mm. For all modes of workpiece displacement speed for the used boron containing envelope with the above-specified thickness a higher thickness of the borated layer and the heat affected area corresponds to a higher thickness of coating. Increase of the spot size leads to an increase in the depth of the layer. By X-ray and metallographic diffraction the phases and structural constituents of the borated layer were decoded. X-ray diffraction and microstructural analysis revealed an association between the exposure speed and share of high-boron layer structures. It is shown that the borated layer in the ductile iron includes such phases as FeB, Fe2B, α-phase, and borocementite Fe3 (B, C). The research results can be extended to other parts subject to intensive wear.