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

Abstract Shot peening is becoming a widely used surface strengthening technique for various key mechanical components as it is well known to have an enhanced influence on the fatigue performance. It allows to strengthen the mechanical properties of material, introduce a certain depth of compressive stress layer and change the surface topography. The relation between shot peening processing parameters and the surface integrity including residual stress and surface roughness remains a large unmet practical need. In this paper, the residual stress and surface topography after various shot peening treatments are experimentally and theoretically examined. A random multi-shots peening model of a carburized roller, accounting for the initial hardness gradient and residual stress, is developed. The measured residual stress and surface roughness are in good agreement with the predicted results. Both the experimental and simulated results reveal that the axial and tangential residual stress components tend to be consistent after shot peening. In addition, the influence of peening coverage on detailed evolution of surface topography and residual stress is investigated. It is found that the ratio between the layer thickness of compressive stress and the critical depth of maximum stress generally lies in the regime of 3.6-4.3 after shot peening. As the coverage increases from 100% to 400%, surface roughness parameters Sa, Sq, S5z, Sku decrease, while the maximum magnitude of compressive stress fluctuates in the range of 1105∼1230 MPa. This work acts as an advisory reference for shot peening engineering practices.