Pathways of Dissipation of Frictional Energy under Boundary Lubricated Sliding Wear of Martensitic Materials

Abstract

The challenges of technical systems subjected to friction and wear become more demanding with steadily increasing stresses. Besides safety matters, failure of tribologically loaded systems can cause tremendous maintenance costs. Because of the lack of a general wear prediction model, tribometer tests must be used in order to investigate wear behaviour of materials in certain tribological systems. Any well-aimed optimizations of tribological contacts requires a comprehensive understanding of friction and wear mechanisms. Otherwise the transferability into technical applications is questionable because of the wide range of applied loads, lubrication conditions, and materials microstructures. In this study, specimens with different topographies and subsurface microstructures were investigated prior to and after tribological testing. The analyses of surface and subsurface characteristics were performed by means of complementary high-resolution electron-microscopy techniques. The study attempted to link the findings to the wear behavior in order to gain information about the pathways of dissipation and transformation of frictional energy into wear. It was found that the dissipation pathways of base body and counter body were different, resulting in diverse tribological behaviour. Nonetheless, the presence of a near-surface grain-refined layers (tribomaterial) supported by a sub-surface strain gradient appears to provide a beneficial influence. Despite the fact that any direct or even conclusive relation to the topographies or subsurface microstructures cannot be given, the discussion provides some hints on how to analyse such systems for their characteristic mechanisms. In addition to the capability of such approach as one step of understanding, its limitations are shown and briefly discussed as well.