A cost-effective optimization approach for improving the fatigue strength of diamond-burnished steel components

Abstract

Diamond burnishing is a surface modification method aimed at improvements in the surface integrity (SI) and operating behavior of metal components. A cost-effective optimization approach for increasing the fatigue strength of diamond-burnished steel components has been developed. The basic idea is that the fatigue strength can be controlled by controlling some of the SI characteristics (surface micro-hardness, hardened-layer depth and roughness) whose measurements are not time-consuming and expensive. Thus, a multi-objective optimization task was set and solved using the weight vector method. The governing factors were the diamond radius and burnishing force. The resulting fatigue limit differed from the maximum fatigue limit by a mere 0.44%, which proves the effectiveness of the proposed approach. The results obtained for the fatigue limit are explained by means of an X-ray analysis of the introduced residual stresses and an analysis of the microstructures of the surface and subsurface layers. It has been established that a greater depth of the affected zone coupled with a smaller gradient in the alteration of the microstructure in depth provides larger fatigue strength.