Fatigue Performance of the Mechanically Surface Treated Steels 42CrMo4 and 54SiCr6: Shot Peening vs. Roller-Burnishing

Author:  Wierzchowski, Ostertag and Wagner
Source:  Conf Proc: ICSP-8 Sept. 16-20, 2002 Garmisch-Partenkirchen, Germany
Doc ID:  2002061
Year of Publication:  2002
Abstract:  
Authors Dariusz Wierzchowski 1) Alfred Ostertag 2) Lothar Wagner 1) 1) Chair of Physical Metallurgy and Materials Technology, Technical University of Brandenburg at Cottbus, Cottbus, Germany 2) Ecoroll AG, Celle, Germany Introduction Mechanical surface treatments such as shot peening (SP) and roller burnishing (RB) are commonly used in industrial applications to improve fatigue life and fatigue strength of cyclically loaded engineering components. These treatments lead to surface layer properties of the work-piece different from those in the bulk. For example, the yield stress in near-surface regions increases due to cold work and resulting high dislocation densities. Owing to the local plastic deformation, residual stresses are generated. In addition, the surface topography is changed. Depending on the surface treated material, other property changes can result from stress-induced martensitic transformations and/or modifications in near-surface crystallographic textures [1]. Work has shown that the fatigue performance of mechanically surface treated high-strength steels is mainly affected by near-surface residual compressive stresses which can largely suppress crack growth from the surface into the bulk of a component [2]. Increasing the strength level of the steels may increase the cyclic stability of process-induced residual compressive stresses and thus, their contribution to the improvement of the fatigue performance [3]. However, the stronger the steels the smaller is the strength differential between shot material and workpiece. As notch sensitivity of steels typically increases with an increase in tensile strength, greater contributions of surface roughness to fatigue crack nucleation resistance may result [4]. The goal of the present investigation was to determine possible strength effects on the improvement of the high cycle fatigue (HCF) performance of high-strength steels by shot peening. For comparison, the effect of roller-burnishing which leads to low roughness was also investigated.