Experimental investigation of plastic contact between a rough steel surface and a flat sintered carbide surface

Experiments were performed in this study using a modified hardness tester. A hard flat specimen made of sintered carbide contacted a flat surface made of 42CrMo4 with a hardness of 2.15 GPa and different topographies after vapour blasting and/or lapping. Nine types of one-process surfaces were created on the steel samples with standard deviations of heights (i.e., Sq parameters) between 0.3 and 6 µm. Six types of two-process textures were characterized by Sq parameters between 1.5 and 3.1 µm, and the standard deviations of the plateau heights, represented by the Spq parameter, were between 0.5 and 1.8 µm. The normal loads in the compression tests were 150, 550 and 950 N. Before and after loading, the steel samples were measured using a white light Talysurf CCI Lite interferometer. A special relocation procedure was used to analyse the topographies in the same location on a given sample before and after loading. Based on surfaces changes, plastic deformations were identified and compared with those obtained using the elastic-plastic contact model at various sampling intervals. It was found that both plastic and calculated elastic-plastic deformations were highly correlated with the plasticity index. Plastic deformations were found to be marginally smaller than the elastic-plastic deformations that were computed at a sampling interval of 12 µm.