Investigation of effects of shot peening process on 50CrV4 steel and determination of optimum process parameters

This study was carried out to examine the effect of shot peened diaphragm springs on vehicle clutch system at different shot type and Almen densities. For this reason, 50CrV4 spring steel which is used as diaphragm spring material in clutch systems is used as test material. For the samples, shot peening was performed in different conditions. These conditions were determined as 6, 8, 10, 12, 14 Almen with S170 balls and 6, 8, 10, 12, 14 Almen with S230 balls. The desired almen intensity was achieved by were kept constant between the nozzle and workpiece distance, peening time and throw angle while the turbine pressure and ball diameter were changed. Microstructure analysis, tensile test, surface roughness test, micro hardness measurement, residual stress amount measurement and diaphragm spring force loss tests were performed to the groups which shot peened at different almen intensity. As a result of the tests , it was determined that the shot peening caused an improvement in tensile and yield strength. In the hardness measurements, it was observed that the decarburisation layer occurred after the heat treatment in the samples decreased and hardness increase from the surface to the material core. In the roughness measurements made from the surfaces of the shot peened materials, it was observed that the surface roughness increased with the increase of the shot size and the surface roughness increased with the increase of the almen intensity. The amount of residual stresses occurring on the shot peened materials results was measured by the Barhkhausen method. It was observed that the amount of residual stress increased and the barkhausen measurement values decreased with the increase of Almen intensity. Finally, the effects of the shot peening conditions on the diaphragm spring and the effects on the clutch system were examined. As a result of the experiments, the optimum process parameters are presented to the proposal as the engineering change in Dönmez Debriyaj company which manufactures clutches.