Relationship between surface characteristics and the fatigue life of deep rolled AISI 4140 steel

Abstract

Deep rolling is an effective and economically viable mechanical surface treatment that induces surface deformation by the action of a rolling tool. It is capable of reducing roughness, increasing hardness and inducing compressive residual stresses on the workpiece surface, thus increasing the fatigue strength of the component. This behavior, however, is only achieved with use of suitable parameters. This work investigates the surface topography and fatigue life of hardened AISI 4140 steel subjected to turning followed by deep rolling under distinct conditions. The ndings indicates that for the turned samples, roughness increases with turning feed rate, resulting in fatigue life reduction. Deep rolling promotes a roughness reduction and an increase in fatigue life and, surprisingly, the samples with the highest surface roughness after turning achieved the longest fatigue lives after deep rolling. The areal power spectral density (APSD) analysis of the surface topography was able to identify distinct effects of deep rolling for each level of pressure used. The morphology analysis indicates an initial loss of orientation, followed by the creation of a new orientation after deep rolling under high pressures. Furthermore, the interaction between deep rolling feed and deep rolling pressure presents a signi cant effect on the roughness parameters, indicating that different behaviors depend on each parameter level used. Deep rolling also affects the form of the fatigue fracture, reducing the number of nucleation sites, and modifying the nal overload fracture site.

Deep Rolling Techniques: A Comprehensive Review of Process Parameters and Impacts on the Material Properties of Commercial Steels

“…A. M. Martins et al [48,49] extensively investigated the effect of DR on the fatigue life of AISI 4140 steel material along with considering the influence of machining parameters. Although it was acknowledged that DR enhanced the fatigue life of turned samples in most instances, in specific cases, DR was not fully effective in eliminating the detrimental effects, particularly in the samples turned with higher feed rates.…”