Evaluation of the friction properties of thermally sprayed coatings

In this paper, one of the tribological tests for the evaluation of friction properties is introduced. The test, named “Block-on-Ring”, (in accordance with the standard ASTM G77) was carried out by the SKODA VÝZKUM Ltd. company and realized on renovated apparatus. The brief description of the measurement is as follows: the flat surface of the sample is pressed against the cylindrical surface of the rotating wheel. Arbitrary oil is fed to the materials’ contact surface and the increasing temperature can be detected using the thermocouple that is placed in close proximity of the contact materials. Using the strain-gauge dynamometer, the friction force is recorded. The test is run on a number of periods and, including after the first expiration time, the wear track formed in the sample is measured and evaluated. The final results are the summary of partial results of the long-standing tests, which serve for the preliminary detection of the friction behaviour of the materials. The friction properties of the thermally sprayed coatings were investigated. The Cr3C2-NiCr, 13% Cr and Cr2O3 coatings were tested. The thin-base babbit was selected as the counter-part. The main interest was in the characterization of the friction properties in the dependence on the amount of added lubricant and on the normal load of sliding couples.