An X-ray diffraction study of the triaxial normal residual stresses in worn aluminum bronze surfaces

In metallic systems subjected to sliding wear material loss often results from the formation and subsequent delamination of a transfer layer. This phenomenon has previously been observed in copper-rich aluminum bronzes. The evidence obtained indicates that wear occurs by the delamination of the layer parallel to the surface in the vicinity of the layer-substrate interface.In general, copper-rich aluminum bronzes exhibit increasing wear rates with increasing aluminum content. Since wear results from the failure of the transfer layer, it is expected that factors which affect the stability of the layer should be related to the observed wear rate. One factor could be the residual stress pattern induced during the wear process. In a previous study the in-plane residual stresses were measured on worn copper-rich aluminum bronze samples. The residual stresses were found to be compressive and of increasing magnitude for increasing wear rate (increasing aluminum content). In this investigation the stresses normal to and at some distance below the surface were measured on samples of compositions similar to those used previously. The normal stresses were found to be tensile and increased in magnitude with increasing wear rate. It is suggested that the development of residual stresses normal to the surface may be an important wear-controlling parameter.