A study on friction coefficient and wear coefficient of coated systems submitted to micro-scale abrasion tests

Several works on friction coefficient during abrasive wear tests are available in the literature, but only a few were dedicated to the friction coefficient in micro-abrasive wear tests conducted with rotating ball. This work aims to study the influence of titanium nitride (TiN) and titanium carbide (TiC) coating hardness on the friction coefficient and wear coefficient in ball-cratering micro-abrasive wear tests. A ball of AISI 52100 steel and two specimens of AISI D2 tool steel, one coated with TiN and another coated with TiC, were used in the experiments. The abrasive slurry was prepared with black silicon carbide (SiC) particles and distilled water. Two normal forces and six sliding distances were defined, and both normal and tangential forces were monitored constantly during all tests. The movement of the specimen in the direction parallel to the applied force was also constantly monitored with the help of an electronic linear ruler. This procedure allowed the calculation of crater geometry, and thus the wear coefficient for the different sliding distances without the need to stop the test. The friction coefficient was determined by the ratio between the tangential and the normal forces, and for both TiN and TiC coatings, the values remained, approximately, in the same range (from μ = 0.4 to μ = 0.9). On the other hand, the wear coefficient decreased with the increase in coating hardness.