A systematic approach for the selection of tribological coatings

Coatings are more and more used to reduce friction or resist wear of contacting surfaces. However, the selection of the optimal coating from many possibilities is still difficult for a given tribological application. In the present work, a systematic approach is suggested to help the selection of tribological coatings. Firstly, a pre-selection tool based on database is developed to pick out several coatings as candidates for performing further tests. In the pre-selection tool, many industrial tribological coatings are included, and they can be ranked according to the extent that they meet the requirements of a given tribological application. Next, some simple evaluation techniques (nanoindentation test, scratch test, ball cratering test, etc.) are used to assess the properties of the candidate coatings to screen out some poor ones. Then, the remaining coatings are tested under the relevant conditions to investigate their tribological behaviors. According to the test results, a dissipated energy density approach can be easily used to evaluate and compare their tribological performance, because the relationship between coating lifetime and dissipated energy density can be fitted as one master curve whatever the values of test parameters. Finally, in view of non-tribological and non-functional requirements, the coatings are synthetically compared using a flexible polar diagram, and a weight point method can assist the comparison.