Influence of shot peening on fatigue durability of decarburized spring steels

The influence of shot peening on high cycle fatigue behaviour of spring steel was investi-gated. The material studied was a quenched and tempered carbon steel 51SiCr7 (0.55 C, 1.9 Si and 0.9 Mn). Three series of fatigue specimens with zero, 0.15 and 0.45 mm depth of decarburization were produced. Half of the specimens from each series were shot peened, leading to a thickness of the compressed surface layer of about 0.25 mm. The specimens were tested in bending fatigue. A 45% improvement in fatigue limit of the decarburized series was achieved after shot peening. The detail of relaxation of the residual stresses was followed and compared for different series of specimens.