An investigation of fretting behavior of ion-plated TiN, magnetron-sputtered MoS2 and their composite coatings

All surface techniques can be roughly divided into two categories: anti-wea r coatings characterized by high hardness and anti-frictions coatings with low friction coefficient. However, it is still unclear which kind of coatin gs is more effective for preventing the fretting damage so far. So it is of important meaning to conduct a comparative study on fretting-resistant beh avior of these coatings. This paper analyzes the fretting properties and da mage mechanism of ion-plated TiN, magnetron sputtered MoS2 and their compos ite coatings on a SRV testing machine through a systematic examinations of wear scar and wear debris under SEM. The main results obtained in the slip regime showed that the fretting resistance of TiN coating was superior to t hat of MoS2 coating, especially at high load and large number of cycles. De tachment of particles was the main reasons of degradation for both TiN and MoS2 coatings, while the shape of the detached particles were quite differe nt. The composite coating of TiN + MoS2 showed excellent fretting-resistant performance under the same testing conditions, as the solid lubrication pr operty of MoS2 coating could be fully developed by a strong support from th e underneath TiN coating, i.e., the advantages and disadvantages of two kin ds of surface techniques could be mutually supplemented. In addition, the f ormation and effect of the third-body is discussed in detail as well. (C) 1 999 Published by Elsevier Science S.A. All rights reserved.