| As a new type of alloy material containing at least four principal elements,high entropy alloy has attracted much attention due to its excellent mechanical properties,good thermal stability and wear resistance.In order to further improve the wear resistance of high entropy alloy,adding carbon element to high entropy alloy to promote the formation of hard precipitate phase is an effective way to improve the wear resistance of materials.The preparation of high entropy alloy materials by powder metallurgy technology and the study of the relationship between microstructure and properties have high research value for the preparation technology,microstructure and properties of high entropy alloy,and have important guiding significance for promoting the application of high entropy alloy in the industrial field.In this paper,CoCrFeMnNiNiCx and AlCoCrFeNiCx high entropy alloys with different carbon contents were prepared by mechanical alloying and discharge plasma sintering using high entropy alloy powder and carbon powder as raw materials.The microstructure,hardness and friction and wear properties of the two series of high entropy alloys were studied.The results show that the properties of the alloys are better than those of the existing high entropy alloys.Specific research contents are as follows:(1)The effects of carbon content on the microstructure evolution,phase change and hardness of CoCrFeMnNix(x=0,0.3,0.6,0.9,1.2)high entropy alloy were studied.The effects of carbon content and load on the friction and wear properties of the alloy were emphatic studied.The results show that the carbon alloyed CoCrFeMnNix high entropy alloy has a two-phase structure composed of FCC phase and M7C3 phase.The effect of carbon addition on the alloy phase shows that the higher the carbon content is,the more obvious the diffraction peak of M7C3 phase is.Carbon alloying can significantly improve the hardness of the alloy and improve the scratch resistance of the alloy.Under the dry friction condition,with the addition of carbon,the wear of the alloy decreases firstly and then increases slightly.Appropriate addition of carbon can greatly improve the wear resistance of the material.The influence of load on the alloy is mainly reflected in the higher the load,the higher the wear degree of the alloy,the main wear under large load is stratified wear and abrasive wear,the main wear under small load is fatigue wear.However,the wear resistance of the alloy increases first and then decreases with the increase of carbon content under four kinds of loads.(2)The effects of carbon content on microstructure evolution,phase change and hardness of AlCoCrFeNiCx(x=0,0.25,0.50,0.75,1.0)high entropy alloy were studied.The effects of carbon content and load on the friction and wear properties of the alloy were emphatic studied.The results show that the addition of carbon causes the phase transformation of AlCoCrFeNiCx alloy powder from BCC and FCC two-phase structure to BCC single-phase structure.The addition of carbon to the AlCoCrFeNi high entropy alloy increases the microhardness of the alloy to a maximum of 578HV,which is 1.2 times that of the alloy without carbon.The addition of carbon has little effect on the friction coefficient of the alloy,which is between 0.68-0.73.When the carbon content is low(x?0.50),the larger the load is,the lower the friction coefficient is;while when x?0.50,the larger the load is,the higher the friction coefficient is.The addition of carbon has a significant effect on the wear resistance of the material.When the carbon content reaches x=0.75,the wear rate can be reduced by at least 80%.However,the continued addition of carbon does not improve the friction resistance.The increase of load will lead to the increase of wear rate. |
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