A mechanical model for surface layer formation on self-lubricating ceramic composites

To predict the thickness of a self-lubricating layer on the contact surface of ceramic composite material containing a soft phase during dry sliding test, a mechanical model was built to calculate the material transfer of the soft second phase in the composite to the surface. The tribological test, as a case, the contact situation of a composite disk sliding against a loaded pin was studied in the model. The macroscopic deformation of the composite was supposed to be elastic. Subsurface stresses were calculated by the Hamilton's formulae. Further, the squeezed second phase material of inclusions was analyzed microscopically based on the Hashin's equations of inelastic inclusions. Based on the mechanical model, the thickness of the transferred layer during the multi sliding passes was predicted. The influence of material parameters and loading conditions such as inclusion (second phase) concentration in the composite, yield strength of the inclusion material, normal load on the pin and friction force were studied. The model can be used to design and optimize self-lubricating ceramic composites for applications and resulting contact conditions.