Complex Wear Measurement on Thin Coatings By The Cratering Method

Ball cratering and rotating wheel tests are useful techniques for abrasive wear resistence evaluation of thin coatings. Nevertheless, such techniques involve significant experimental errors, coming from equipment deficiences and changes in wear response depending on test parameters. In case of rotating wheel test, common instrumental errors are: geometry-induced errors (curved or non-horizontal sample surface), alignment errors (misalignment between ball/wheel axis and sample stage) and optical measurement errors. In the present paper, errors due to crater dimension detection system (penetration depth or crater diameter) and equipment deficiences (rotating axes misalignment and sample slope) were numerically analysed. A general expression form volume calculation was obtained, considering axes misalignment and sample slope, and experimentally validated by wear tests on Ti/TIN CAE-PVD coatings and profilometer abraded volumes measurement. Results showed that axes misaligment and sample slope involve considerable errors in wear coefficient evaluation. However, errors can be corrected by the use of obtained expressions.