Study On Preparation Of Chromium Oxide Film And Its Self-lubricating Performance In Wide Temperature Range

In this experiment,a series of chromium oxide films with different oxygen flow were prepared on the surface of Inconel718 superalloy by multi arc ion plating technology.The structure and tribological properties of the films were characterized accordingly.Using the diffusion effect of grain boundary elements of nickel-based superalloys at high temperatures,a chromium oxide film with a network-like convex structure was obtained,and its wide temperature range self-lubricating properties were studied accordingly,and the conclusions are as follows:（1）As the oxygen flow rate increases,the surface of the film becomes smooth and dense,and its growth mode undergoes a change from columnar crystals to dislocation-stacked nanocrystals to columnar crystals.At the same time,as the oxygen flow rate increases,the phase composition of the film changes from Cr₂O_2.4to Cr₂O₃,and the degree of crystallization becomes more complete.In terms of mechanical properties,as the oxygen flow rate increases,the bonding strength between the film and the substrate gradually decreases.In terms of tribological performance,under room temperature conditions,except for the oxygen flow rate of 110 sccm,the films at other flow rates fail quickly within a short distance.The film under 110 sccm has good resistance to wear and plastic deformation,and can maintain good tribological properties from RT to 800℃.Its friction coefficient is stable between 0.27～0.30 at high temperature except for 0.49 at room temperature.Meanwhile,it has the lowest wear rate under the test condition of 800℃,which is 4.03×10^–6mm³/（N·m）.（2）After annealing at 1000℃,the surface of the chromium oxide film on Inconel718 superalloy will form network convex structure,which greatly improves the mechanical and tribological properties of the film.The annealed film can meet the requirements of continuous lubrication from room temperature to 1000℃,and has a certain high temperature self-healing ability.The high temperature phase transformation,element diffusion,lubrication mechanism and self-healing mechanism of the films during annealing were studied.（3）Inconel 718 and GH4169 nickel-based superalloys were annealed at 1000℃,and their structures and properties before and after annealing were tested.The results show that there is little difference in the structural composition between the two superalloys,but the grain size,mechanical properties and tribological properties are greatly different.The overall performance of Inconel718 is better than that of GH4169,and it has good mechanical and tribological properties after high temperature annealing at 1000℃.