| Ceramic-based self-lubricating material is one of the most effective ways to solve the problem of high temperature lubrication,and has great application prospect in high-end equipment.At present,the research on Cr2O3 is mainly focused on surface treatment,and there are few studies on introducing Cr2O3as the second phase into ceramic composite.Based on the integrated design principle of advanced ceramic structure/lubrication function,Al2O3/Cr2O3 three-dimensional structural ceramic composite with high strength,wear resistance,oxidation resistance and excellent ultra-high temperature self-lubricating properties were successfully prepared in this study.The failure evolution mechanisms of materials under the thermal-mechanical-friction coupling effect of ultra-high temperature,high load,strong oxidation and high speed was investigated.The effect mechanism of structure and structural parameters on high temperature friction,wear properties and high temperature oxidation resistance of materials was revealed.The main conclusions are as follows:(1)The Al2O3 coated Cr2O3 core-shell structure particles were successfully prepared by the mechanical mixing method,and the Al2O3/Cr2O3 three-dimensional structure ceramic composite was successfully prepared by the lamination/monolithic pressing-dry pressing-plasma sintering process.By comparing its microscopic morphology,it was found that the composite obtained by lamination pressing has an obvious"brick-mud"staggered stacked structure,and its apparent density,bulk density and relative density are slightly higher than the material obtained by pressing.(2)Al2O3/Cr2O3 three-dimensional structure ceramic composite can effectively combine the high bearing ability of continuous Al2O3 ceramic and the high-temperature lubrication of Cr2O3,so that the material can maintain excellent load-bearing capacity,anti-friction and anti-wear properties at 800?.The compressive strength of the material at 800?can reach about 630 MPa,which is 12%higher than that of homogeneous Al2O3/Cr2O3 composite;the bionic structure design of composite can improve enrichment degree of Cr2O3 on the friction surface of the material to a certain extent,which is more conducive to the formation of lubricating film and transfer film on the surface of the friction pair,there by significantly reducing the friction coefficient and wear rate between the materials.When the particle size of Cr2O3 is 250?m,the friction coefficient and wear rate of the material can be as low as 0.35 and 3.1×10-6 mm3·N-1m-1,respectively,which are 29%and 73%lower than those of the homogeneous Al2O3/Cr2O3 composite.(3)The wear resistance of Al2O3/Cr2O3 three-dimensional structure ceramic composite is different under different loads.On the whole,the material Al-Cr250possesses the most excellent wear resistance,while the material Al-Cr150 presents poor wear resistance.In the load range of 20N?35N,the friction coefficient of material Al-Cr250 is between 0.35 and 0.46,and the wear rate is less than 3.1×10-6mm3·N-1m-1.The friction coefficient of material Al-Cr150 is between 0.46 and 0.54,and the wear rate fluctuates between 3.1?11.0×10-6 mm3·N-1m-1;the friction coefficient of material Al-Cr350 fluctuates between 0.37?0.48,and the wear rate is between 3.2?6.8×10-6 mm3·N-1m-1.When the load is 35N,the friction coefficient of material Al-Cr250 can be as low as 0.35±0.04;the self-lubricating performance of material Al-Cr350 is second,and its friction coefficient can be as low as 0.37±0.02.However,the friction coefficient of material Al-Cr150 is relatively large about0.46±0.04.(4)Both Al2O3 ceramic phase and Cr2O3 high temperature solid lubricants have excellent high temperature oxidation resistance.After being treated in a high temperature water and oxygen environment at 1400?,Al2O3 ceramic have the largest mass loss rate with a mass loss rate of about 0.29%;The mass loss rate of Cr2O3 sintered body is about 0.16%.After Al2O3/Cr2O3 composite material is treated in high temperature water and oxygen,the Cr2O3 component has undergone thermal diffusion and agglomeration in the material.However,Al2O3 ceramic was still evenly distributed.The three-dimensional continuous structure of Al2O3 matrix remained intact,and the mass loss rate was less than 0.05%.Thus,the combination of Al2O3and Cr2O3 is more conducive to the improvement of high temperature oxidation resistance. |
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