Modelling surface texture evolution for a titanium carbide implanted tool surface undergoing wear

Abstract

Tribological behaviour (friction and wear) during the forming of sheet metals is strongly influenced by the presence of very small scale (nano-metric) surface structures, or textures, on the sheet or tool surface. Although of very small size, surface textures are able to carry pockets of lubricant into the heavily loaded tool-workpiece contact, leading to reductions in friction and tool wear. Such surface textures are also found to be critical in determining the surfacefinish after painting for products such as car body panels which are produced by forming operations. Indirect Structuring, or Self-Forming [1] produces a tool surface structure in a two stage process, and this structure is maintained during further wear of the surface. The process depends on implanting the tool surface with an array of metal carbide implants, giving repeating local gradients of material properties across the surface. This paper describes an experimental and accompanying theoretical model for prediction of the height difference between such implants and the surrounding substrate following wear. To reveal the key mechanisms which determine the surface texture the problem has been reduced to the study of a single thermal implant idealised as a cylinder of implant material surrounded by a concentric cylinder of the substrate.