Influence On Shot Peening And Blast Polishing For Rotating Bending Fatigue Strength Of Vacuum Carburized Steel With Circumferential Notch

In order to improve fuel efficiency in automobiles, weight reduction is necessary as well as improving engine efficiency. For transmission gears, thickness reduction is necessary for weight reduction. When the thickness is reduced, the cross-sectional area becomes smaller, and the load stress increases. Therefore, higher fatigue strength is required. Most gears carry out carburizing. Shot peening is often used to improve the fatigue strength of carburized heat-treated parts. After shot peening, compressive residual stress is introduced, but at the same time, surface roughness is increased. Therefore, the processing conditions of shot peening are very important. Blast polishing is a processing method in which resin media containing abrasive grains is sprayed at the workpiece. Compared to other polishing methods, the processing time is short. In addition, it is easy to apply to complex shapes. In this study, shot peening and blast grinding were carry out on circumferential notch specimens to improve the fatigue strength of vacuum carburized materials commonly used in automotive transmission gears. As a result, the fatigue limit of test pieces applied with double shot peening improved by 81% compared to unprocessed specimens, blast polished specimens which are carry out double shot peening achieved a 100% improvement in fatigue limit compared to unprocessed specimens. This is due to compressive residual stress and low surface roughness.