【作者】 张波；

【导师】 王树奇；

【作者基本信息】 江苏大学 ， 材料工程（专业学位）， 2017， 硕士

【摘要】 钛合金因其优异的综合性能而被广泛应用于诸多工业领域,但较低的塑性剪切抗力和摩擦氧化物的微弱保护作用使其耐磨性较差,阻碍了其应用。因此,改善钛合金的摩擦学性能具有重要的理论意义和工程应用价值。本文在TC11合金/GCr15钢滑动界面上添加多层石墨烯/Fe2O3复合材料,以改善钛合金的摩擦磨损性能。作为对比,同时研究了TC11合金在未添加及单独添加多层石墨烯或Fe2O3纳米颗粒下的摩擦磨损行为。采用XRD、SEM、EDS等微观分析手段对磨损表面及亚表面的形貌、结构及成分进行全面测试,重点表征了摩擦层的特征,分析了摩擦层的形成过程、作用及对摩擦磨损性能的影响,并探讨了磨损机理。结果表明,TC11合金的摩擦磨损行为与添加剂种类及载荷、添加量密切相关。单独添加多层石墨烯时,无论何种载荷或添加量,TC11合金的磨损量均比未添加时高很多,平均摩擦系数也较大。单独添加Fe2O3纳米颗粒时,低载下磨损量较低,但平均摩擦系数很高;高载下,无论何种添加量,磨损量和平均摩擦系数均较大。对于多层石墨烯/Fe2O3复合材料添加剂,在载荷20-100N或添加量0.2-0.4g下,TC11合金的磨损量和平均摩擦系数均极低;而当载荷增大至120N或添加量减小至0.1g时,磨损量和平均摩擦系数均快速升高。研究发现,当添加不同种类纳米材料时,磨损表面均形成成分各异的摩擦层,其不同的作用显著影响TC11合金的摩擦磨损性能及磨损机理。单独的多层石墨烯添加剂吸附至磨面形成摩擦层,其因含多层石墨烯而具有润滑作用,但弱的承载能力使其易于失去稳定性和保护作用,TC11合金的耐磨性未得到提高,此时的磨损机理与未添加时类似,主要为粘着磨损和磨粒磨损。单独添加Fe2O3纳米颗粒时,摩擦层的形成依靠摩擦烧结,含Fe2O3的摩擦层承载能力较强,TC11合金在低载下的耐磨性显著提高,但摩擦性能并未改善;而在高载及任一添加量下,无润滑的摩擦层在滑动中途失效,导致严重磨损的出现。当添加多层石墨烯/Fe2O3复合材料时,两组分依次经历烧结和吸附形成主要含Fe2O3和主要含多层石墨烯的摩擦层,双层摩擦层因其良好的承载、润滑能力而具有优异的协同保护作用,在较高载荷或较少添加量下可稳定存在至滑动结束,故发生轻微磨损,TC11合金的摩擦磨损性能同时得以显著改善。更多还原

【Abstract】 Titanium alloys are widely used in various industrial fields because of their excellent combination properties.However,the poor wear resistance of titanium alloys,resulting from the low plastic shear resistance and the weak protection of tribo-oxides,hinders their applications.Therefore,it possesses important theoretical significance and engineering application value to improve the tribological performance of titanium alloys.In this paper,the multilayer graphene/Fe2O3 composite was added to the sliding interface of TC11 alloy/GCr15 steel to improve the friction and wear performances of titanium alloys.As a comparison,the friction and wear behaviors of TC11 alloy with no and pure multilayer graphene or Fe2O3 additives were simultaneously studied.The morphology,structure and composition of worn surfaces and subsurfaces were thoroughly measured by the microscopic analysis methods of XRD,SEM and EDS.The characteristics of tribo-layers and their formation process and function were analyzed.The effect of tribo-layers on the friction and wear performances and wear mechanism was explored.The results show that the friction and wear behaviors were closely related to additive types as well as loads and additive amounts.When adding pure multilayer graphene,irrespective of the load or additive amount,the wear loss of TC11 alloy was much higher than that without additives,and the average friction coefficient was also high.For the pure additive of Fe2O3 nanoparticles,the wear loss was low but the average friction coefficient was extremely high under low loads.With an increase of load,the wear loss and average friction coefficient were relatively high,regardless of the additive amounts.For multilayer graphene/Fe2O3 composite additive,the wear loss and average friction coefficient of TC11 alloy were extremely low under the load of 20-100 N or additive amount of 0.2-0.4 g.With an increase of load to 120 N or a decrease of additive amount to 0.1 g,the wear loss and average friction coefficient rapidly increased.It was noticed that the tribo-layers with different compositions were always formed on the worn surfaces,when various nanomaterials were added.Their function would markedly affect the friction and wear performances and wear mechanism of TC11 alloy.The pure multilayer graphene additive could adsorb to the worn surface to form a tribo-layer,which possessed lubricant function because of the existence of multilayer graphene.But this tribo-layer readily lost stability and protection,due to the weak load-bearing capacity.Thus,the wear resistance of TC11 alloy was not able to be improved,and the main wear mechanism was similar to that with no additives,i.e.adhesive wear and abrasive wear.When pure Fe2O3 nanoparticles were added,the formation of tribo-layer depended on tribo-sintering.Under low loads,the wear resistance but not the antifriction performance of TC11 alloy was obviously improved,due to the relatively strong load-carrying capacity of Fe2O3-contained tribo-layer.With an increase of load,the severe wear appeared,irrespective of the additive amount.This was ascribed to the failure of unlubricated tribo-layer during sliding.For multilayer graphene/Fe2O3 composite additive,Fe2O3-predominated and multilayer graphene-predominated tribo-layers were orderly formed by sintering and adsorption.The double-layer tribo-layer possessed excellent synergistic protection effect because of good load-bearing and lubricant capacity.It would steadily exist to the end of sliding under relatively high load or low additive amount,and the mild wear occurred.As a result,an obvious and simultaneous improvement for the friction and wear performances of TC11 alloy was achieved.更多还原