Design And Preparation Of Chromium Oxide Based Ceramic Films And Study Of Wide Temperature Range Tribological Properties

In this thesis,chromium oxide ceramic films were prepared on two high-temperature alloys based on iron and nickel using multi-arc ion plating technique.The effect of alloy element diffusion on the structure and properties of chromium oxide films during high-temperature annealing was investigated,and the mesh-like bulge structure formed on the film surface after annealing resulted in excellent tribological properties in a wide temperature range.In addition,from the perspective of structural design multilayering,Cr YO films with high stability at high temperatures were prepared by doping chromium oxide films with rare earth element Y to control the volume expansion of the films at high temperatures while ensuring low friction..The main research contents and conclusions are as follows:（1）Two kinds of high-temperature alloys,iron and nickel-based,were annealed at1000°C for 2 h under atmospheric conditions,and the results showed that the two alloys had formed an obvious bulge structure on their surfaces,and the bulges of the nickel-based alloys were linked to each other to form a mesh-like structure.During the annealing process,the formation of a dense amorphous silicon oxide layer at the oxide/substrate interface of the iron-based alloy can block the further inward intrusion of oxygen,while the nickel-based alloy does not have a dense silicon oxide layer to block it,and the Ti and Nb elements in the alloy are severely biased and oxidized at the grain boundaries,so the formed bulge structure is also more obvious.（2）Chromium oxide films were deposited on the surfaces of two high-temperature alloys,iron and nickel-based.After high-temperature annealing treatment,it was found that the Cr₂O₃ films deposited on the nickel-based alloy formed a net-like raised structure similar to that of the alloy,while for the iron-based alloy,the Mn Cr₂O₄ with a thermally stable octahedral spinel structure formed by the diffusion of Mn elements onto the film surface could inhibit further oxidation of the elements in the substrate at high temperatures,so there was no obvious raised structure on the film surface.Compared to iron-based alloys,the mesh-like bulge structure formed on the surface of chromium oxide films on nickel-based alloys plays a good role in friction reduction during the friction process,and thus has a lower friction coefficient and wear rate over the entire temperature range.（3）Cr YO films with different Y contents were designed and prepared,and also studied in comparison with Cr₂O₃ films.The results showed that the densification of the films increased significantly with the doping of Y elements and showed a multilayer structure consisting of alternating Cr Ox and YOx.After high-temperature annealing treatment,it was found that the doping of Y elements could inhibit the phase segregation and oxidation processes by blocking the fast diffusion tracks along the grain or columnar boundaries of the Cr YO films,thus exerting a beneficial effect on the antioxidant behavior of the films.In addition,at high temperature,the multilayer structured Cr YO films generate interlayer slip under the action of frictional shear,thus providing good high temperature lubrication.