| In this thesis,the tribological properties of Si3N4-hBN composite ceramics with titanium alloy and stainless steel in Cu2+ corrosion solution were systematically studied,and the wear mechanism and friction reduction mechanism were analyzed.The influence of pH value of Cu2+ corrosion solution and the matching materials on the friction pair were revealed.At the same time,the corrosion resistance of the composite ceramics in acidic Cu2+rich corrosion solution was preliminarily investigated,and the effect of corrosion time and hBN content on the corrosion behavior was revealed.The research results of this paper are described as follows.(1)In the neutral corrosive solution environment,with the increase of hBN content,the friction coefficient of the composite ceramics and 2507 plate decreases from 0.679 to 0.15 of Si3N4-30wt.%hBN,and the wear rate of the pin and plate is not higher than 10-4mm3/Nm,especially when the hBN content reaches 30%.The wear rate of the pin is reduced to close to 0,which is mainly due to the formation of the tribochemical reaction products containing B-O and Si-O and the replacement products Cu and its oxides on the worn surface of the Si3N4-30wt.%hBN.When composite ceramics and titanium alloy pair,the friction coefficient is not less than 0.4,the wear rate is also in the order of 10-4mm3/Nm,the wear mechanism is mainly abrasive wear and adhesion wear,which is mainly due to the addition of hBN can not form an effective protective lubrication film on the surface,only due to the increase of hBN content,the composite ceramic surface formed spalling crater.As a temporary liquid storage pool,play a certain role in weakening mechanical wear.(2)With the increase of hBN content,the friction coefficient decreases from 0.691 of pure Si3N4 to 0.139 of Si3N4-30wt.%hBN,and the wear rate of both pin and plate is not higher than 10-4mm3/Nm.It is found that the surface of the friction pair forms a more continuous reaction film containing B-O,Si-O and the precipitation layer of Cu and its oxides,which play a good synergistic effect on friction reduction,and the friction pair shows a lower friction coefficient and wear rate.The friction coefficient of SN30/TC4 is as high as 0.534,and the wear rate is not lower than 10'4mm3/Nm.The surface film is not formed on the friction surface,and the wear mechanism is mainly mechanical wear.(3)The results show that the acid environment is favorable to the formation of the tribochemical reaction film and the precipitation layer containing copper,and it is easier to form the tribochemical reaction film on the surface of the composite ceramic and duplex stainless steel pair to play the role of protection and lubrication,and obtain a lower friction coefficient and wear rate.At the same time,the static corrosion test results further indicate that Si3N4-hBN composite ceramics have good corrosion resistance.The static corrosion test results also showed that Si3N4-hBN composite ceramics possessed good corrosion resistance.In summary,the Si3N4-hBN composite ceramic material exhibited better tribological performance and corrosion resistance in acidic Cu2+corrosion solution.The formation of protective lubricating film and precipitation layer is the essential reason of excellent friction and wear performance.The research results of this thesis have practical value for expanding the application fields of Si3N4-hBN composite ceramics,and have academic significance for enriching the theory of ceramic tribology. |
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