Effect Of Artificial Tribo-layers On Dry Sliding Friction And Wear Performances Of TC11 Alloy

Titanium alloys are widely used in various fields because of their excellent combination properties,but the poor friction and wear performances limit their applications.The wear resistance of titanium alloys could be markedly improved via the formation of an artificial tribo-layer.However,there lacks deep and systematical researches on their destruction and function mechanism and effect of the artificial tribo-layers with various structures on friction and wear performances of titanium alloys.In this paper,Fe₂O₃,multilayer graphene and MoS2 nanomaterials with different mixture methods composite were added to the sliding interface of TC11 alloy/GCr15 steel to prepare the artificial tribo-layers.The effect of these layers on the friction and wear behaviors of TC11 alloy under various loads and sliding speeds was studied.Phase,morphology and composition of worn surfaces and subsurfaces of TC11 alloy before and after second wear were thoroughly analyzed by the methods of XRD,Raman,SEM and EDS.Based on the characteristics variation of artificial tribo-layers,their destruction process was studied.Further,the function mechanism of various artificial tribo-layers and their effect on friction and wear performances of TC11 alloy were explored.This research will provide scientific basis for the tribological design of titanium alloys,and possess important theoretical significance and engineering application value.The results show that irrespective of the load or sliding speed,the wear loss and average friction coefficient of TC11 alloy were always high with the additive of Fe₂O₃,which were similar to that without additives.When multilayer graphene/Fe₂O₃ composite or MoS2+Fe₂O₃ mechanical mixture were added,the wear loss and average friction coefficient were low under a certain sliding conditions,but they linearly increased with the load and speed.For the additive of multilayer graphene+Fe₂O₃ mechanical mixture,the wear loss and average friction coefficient almost maintained extremely low values in the whole range of loads and speeds.It was noticed that the artificial tribo-layers with different structures were inductively formed on the surface of TC11 alloy by adding various nanomaterials onto the siding interface.Fe₂O₃ nanoparticles promoted a formation of single tribo-layer,but it was readily destructed because of a lack of lubricity.The worn surface presented adhesion,tearing trace and furrows,and plastic deformation occurred at worn subsurface.MoS2 and Fe₂O₃-contained mechanically mixed tribo-layer,as well as multilayer graphene and Fe₂O₃-contained double-layer tribo-layer,simultaneously possessed lubricant and load-bearing capacity.Thus,they were facile to be retained to the end of second wear.However,a symmetrical distribution for the components in the mechanically mixed tribo-layer and unobviously layered double-layer tribo-layer limited an effective exertion of lubrication.This leaded to a destruction of tribo-layers under relatively high loads or speeds.The worn surfaces and subsurfaces presented furrows,adhesion trace and plastic deformation.The double-layer tribo-layer formed by adding multilayer graphene+Fe₂O₃ mechanical mixture possessed extremely excellent lubrication due to more obvious layering.They would steadily exist and not be destructed under almost entire conditions.The single artificial tribo-layer could not improve the friction and wear performances of TC11 alloy.It is obviously layered double-layer artificial tribo-layer that markedly improved the wear resistance and antifriction performance of TC11 alloy,compared with the mechanically mixed artificial tribo-layer and unobviously layered double-layer artificial tribo-layer.