| Aluminum alloy has been widely used and studied in the mechanical industry.However,the low surface hardness,high friction coefficient,poor wear resistance and corrosion resistance severely limit the effective application of aluminum alloy and its performance.Therefore,the surface modification of aluminum alloy to reduce the friction and improve wear resistance properties has important academic and engineering values.In this paper,combined with simulation and experiment,the methods of modifying the surface of aluminum alloy by laser micro-texture and graphite coating were proposed.Moreover,the synergistic effect of the two modifying methods on the tribological properties was studied.The research work was carried out as follows:Based on the Reynolds equation,the lubrication models of the micro-texture on the surfaces of the friction pairs were established.The lubrication model was numerically analyzed by FLUENT software.The effects of micro-texture morphology and geometric parameters on the pressure and distribution of the lubricant film between the friction surfaces were studied.The results show that under the condition that the depth of the micro-pits is constant,the dynamic pressure lubrication effect is enhanced with the increase of the diameter of the micro-pits,but when the diameter exceeds 100μm,the growth rate becomes slower.Considering the range of contact area between the surfaces of steel ball and the substrate,the circular/square micro-pits with diameters/side lengths of 50 μm,60 μm,80 μm and 100 μm are selected as the research objects of the subsequent experiments.The regularly arranged pit-type micro-textures were prepared on the surface of aluminum alloy specimens by pulsed Nd: YAG laser processing system.The micro-hardnesses of the micro-textures margins were examined by TMHV-1000 microhardness tester.The surface friction and anti-wear properties of aluminum alloy substrates were studied by a HSR-2M-type high-speed reciprocating friction and wear tester,and the effects of surface micro-texture morphology,geometric parameters and the sliding speed on tribological properties were studied.The results show that the average friction coefficient of the microtextured surface is less than that of the non-textured surface,and the degree of wear of the microtextured surface is lower.On the microtextured surface,the higher sliding speed is beneficial to reduce the friction coefficient.Within the range of micro-texture parameters studied,the circular micro-texture has the best anti-friction and anti-wear effect when the diameter is 60μm and the areal density is 4.72%;while when the side length is 80 μm and the areal density is 7.94%,the antifriction and antiwear effects of the square micro-texture are the best.The solid graphite coating was sprayed on the surface of the smooth aluminum alloy substrate and the surface of the micro-textured substrate by thermal spraying.The compositions of the aluminum alloy substrate and graphite coating were analyzed by JSM-6490 LV spectrometer.The surface roughness of the samples was tested using a JB-1C roughness meter.The effects of single-factor micro-texture and graphite coating on the friction and wear properties of the specimen surface were investigated by friction and wear experiments.Moreover,the synergistic effects of the two modifying methods on the antifriction and anti-wear mechanism properties were studied.The results show that the synergistic effect of micro-texture and graphite coating has significant anti-friction and anti-wear effect on the surface of aluminum alloy.The surface has the lowest friction coefficient and has good protection of the surface of aluminum alloy substrate.Through the above researches,the tribological properties of the aluminum alloy surface have been improved,and the theoretical basis and experimental guidance for the performance of the aluminum alloy have been provided. |
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