Effect of shot peening coverage on residual stress and surface roughness of 18CrNiMo7-6 steel

Shot peening is currently becoming a widely used surface strengthening technique that can refine the material grain, increase the hardness and introduce a certain depth of residual compressive stress layer. At the same times it changes the surface topography which may have a deleterious effect on the contact fatigue life. A fully understanding on the mechanism of shot peening for high-strength steels is to be explored. In this paper, the effect of shot peening coverage on residual stress, surface roughness, microhardness and microstructure of rollers are experimentally investigated. Experimental results show that the shot peening leads to a slight increase of surface and near-surface hardness from 690 HV to 740 HV, and an appreciably increasing of the subsurface maximum compressive residual stress. Moreover, some retained austenite in the the near-surface layer are transformed to martensite after shot peening, and wherein the grain refinement occurs.

Effect of shot peening coverage on hardness, residual stress and surface morphology of carburized rollers

Investigation on the effect of shot peening coverage on the surface integrity

Shot peening is widely used to strengthen the surface of metal parts, and its effect is affected by various parameters, such as shot peening coverage, peening intensity, peening velocity, shot size and shot material. In this study, a random multi-shots model which incorporated dislocation density-based constitutive equations was established. With the developed model, the effects of peening velocity, peening coverage and double peening on the surface integrity in terms of the residual stress, surface roughness and dislocation cell size were analyzed. The simulated results show that increasing the peening velocity can significantly thicken the refining layer and the compressive residual stress layer (CRSL), and deepen the location of the maximum compressive residual stress (MCRS). Meanwhile, increasing the peening coverage can heighten the magnitude of MCRS in subsurface, but hardly affects the surface compressive residual stress (SCRS) and the thickness of CRSL. Compared to simply pursuing the improved peening velocity and enhanced coverage, the use of an appropriate double peening process can induce a larger SCRS while reduce the surface roughness slightly.

Effects of different shot peening parameters on residual stress, surface roughness and cell size

Shot peening is widely used to improve the fatigue properties of components and structures. Residual stresses, surface roughness, and work hardening are the main beneficial effects induced in the surface layer from shot peening, which depend on the correct choice of the peening parameters. In this investigation, experiments were designed using the full factorial design of experiment (DOE) technique and an air blast type of shot peening machine. Effects of process parameters such as pressure, shot size, stand-off distance, and exposure time on surface microhardness for AISI 1045 and 316L materials were investigated. An ANOVA was carried out to identify the significant peening parameters. In the case of 316L material, the maximum surface hardness was found to be in the range of 450–824 Hv, whereas it was found to be in the range of 314–360 Hv for AISI 1045. A critical assessment was made so as to understand the variation of microhardness in the direction of peening. Empirical equations between the peening parameters and the surface microhardness for both materials were developed, which are useful in predicting the surface microhardness. It is believed that this technique could prove beneficial in industries for reduction of performance variation and cost and to increase productivity.

D.V. Girish

Papers

Influence of shot peening on the surface durability of thermomechanically treated En 24 steel spur gears

Surface integrity studies on shot-peened thermal-treated En 24 steel spur gears