Study On Modification Of Tribo-layer Of Titanium Alloy

Titanium alloys are widely used in various industrial fields because of their excellent comprehensive properties.However,the poor wear resistance of titanium alloys has always hindered their application.Therefore,the improvement of the wear resistance has become one of the research hotspots of titanium alloys.By artificially adding nanoparticles to modify the tribo-layer formed on the surface of titanium alloy,the wear resistance can be effectively improved.The research has important theoretical significance and engineering application value.In this study,a pin-on-disk type friction and wear tester was used,and TC4 alloy and GCr15 steel were used as friction pairs to carry out the wear experiment with the addition of nanoparticles.The effects of different ratios of MgO,SiO₂,Fe₂O₃ and MoS₂ on the wear behavior of titanium alloy at room temperature were investigated.The morphology,structure and composition of the worn surface,subsurface and tribo-layer were characterized by SEM,EDS and XRD.The effects of different nanoparticles and the modification for tribo-layer were studied,and the wear mechanism was also discussed.The results show that when mixed nanoparticles with different ratios were added on the sliding surface,a protective tribo-layer would form on worn surfaces and had a significant effect on the wear resistance and wear mechanism of TC4 alloy.In the case of dry sliding（no addition）,the weight loss of the wear increased linearly with the increase of the load,and the wear mechanism was severe abrasive wear and adhesive wear.As MoS₂ nanoparticles were added separately,the wear loss was slightly reduced under low load,but was slightly increased under high load.The addition of MgO nanoparticles alone increased the wear loss significantly.The addition of SiO₂nanoparticles alone reduced the wear loss slightly,but with an increase of load,increased significantly.However,50%MgO+SiO₂ or 50%SiO₂+MoS₂ mixed nanoparticles significantly reduced the wear loss.The addition of Fe₂O₃ nanoparticles significantly reduced the wear loss and tends to zero.50%Mix（MgO+SiO₂）+MoS₂and 50%Fe₂O₃+MoS₂ maintained the wear loss of the TC4 alloy at a low value,almost zero,under all load conditions.In these cases,the wear mechanism turned into a mild wear.It has been found that the addition of various nanoparticles causes the modification of tribo-layer from a non-protective tribo-layer to a protective one.The acting mechanisms of various nanoparticles are summarized as follows.MoS₂nanoparticles mainly play a lubricating role to form a protective tribo-layer under low load,but with the increase of load,it is destroyed due to poor bearing capacity.The MgO nanoparticles are not readily form a tribo-layer,and mainly serve as a third body to aggravate wear.Even if it is used together with MoS₂,a protective tribo-layer could not be formed.SiO₂ nanoparticles can form a protective tribo-layer,but its lubricity was poor.So,the tribo-layer is easily destroyed with the increase of load.In this case,the MoS₂ would enhance the protection of the tribo-layer.However,the addition of equal proportions of MgO and SiO₂ could form a continuous,dense and stable tribo-layer with a protection.The Fe₂O₃ nanoparticles readily agglomerated and sintered to form a tribo-layer with a strong bearing capacity and extremely protective function.As it was used in combination with MoS₂,the bearing capacity and the protective function would be further enhanced.