Enhancement of thermal stability and high-temperature oxidation resistance of chromium oxide-based films by addition of rare earth element Y

Chromium oxide ceramic materials are widely used in high-temperature applications requiring high wear resistance and lubricity. To further improve the friction and wear performance and high-temperature stability of chromium oxide thin films, this study attempted to dope rare earth (RE) element Y (yttrium) and deposited CrYO high-temperature self-lubricating ceramic thin films with different doping levels on the surface of IN718 alloys by using multi-arc ion plating technology. The deposited films were annealed at 1000 °C for 2 h under atmospheric conditions to analyze the changes in phase composition and thickness, and the friction and wear characteristics of the CrYO films were tested using a high-temperature friction and wear tester in the temperature range of 25 to 600 °C. The results show that the CrYO-2 film has a dense multilayer structure, and the multilayer oxide film produces interlayer sliding under frictional shear, thus providing lubrication. In particular, the friction coefficients are as low as about 0.25 in the middle and high-temperature sections (400, 600 °C), which provides good high-temperature tribological properties. In addition, the doping of Y elements dramatically affects the formation of the oxide layer and the distribution of voids in the film, changing the diffusion process of the elements of the base material inside the film and at the film-air interface at high temperatures. After two annealing treatments, the film thickness increased from 1.81 to 2.25 μm, and the volume expansion of the films was effectively controlled compared with that of the Cr2O3 films.