Assessment of the possibility of the application of a CrN+OX multi-layer coating to mitigate the development of fretting wear in a press-fit joint

As part of laboratory tests, the macroscopic and microscopic observations of the shaft top layer wear and the microscopic observations of the sleeve/shaft joint surface were conducted. Macroscopic observations demonstrated the occurrence of fretting wear at shaft surfaces in both sample groups under testing, however, the range of wear occurring in samples with the CrN+OX coating was much smaller. The microscopic observations of shaft surfaces revealed a similar image of fretting in both sample groups under testing, such an image consisting of wear in the form of material build-up, microgaps, micropits and microcracks. The chemical analysis of wear products demonstrated their plastic deformation and oxidation. Scientific research indicates that adhesion is the process initiating the development of fretting wear; in these tests an attempt was made to eliminate adhesion. The application of the coatings under testing produced the expected result. The appropriate hardness of the shaft top layer with coatings caused the mitigation of adhesion thus significantly reducing the development of fretting wear.