Role of heat treatments in the improvement of the sliding wear properties of Cr3C2–NiCr coatings

Thermal sprayed Cr3C2–NiCr coatings are widely used due to their excellent properties such as hardness and wear resistance, even at high temperatures or in corrosive environments. During thermal spraying, oxidation as well as Cr3C2 dissolution takes place. The present paper analyses the possibility of improving the sliding wear resistance of these coatings using heat treatments carried out at different temperatures in an inert atmosphere and in an oxidising atmosphere. An enhancement of the sliding wear resistance attributed to the precipitation of Cr3C2 is demonstrated. Substantial differences are found in samples treated under the different atmospheres due to the role of the oxides formed on the tribological behaviour of the coatings. Sliding wear tests were carried out using Ball-on-Disk equipment and the wear tracks were studied by scanning electron microscopy and scanning white light interferometry. A relationship between wear damage and energy dissipated during the sliding wear tests is found. In addition, the abrasive wear resistance of the coatings assessed by the Rubber Wheel test is reported.