Effect Of Solid Carburization On The Frictional Behavior Of Ti6Al4V Alloy

With the development of the defense industry and the modernization of medical materials,the application of light metal materials is becoming more and more widespread.Ti6Al4V alloy has special excellent characteristics,such as high specific strength,low density,non-magnetic,high temperature resistance and high corrosion resistance,which makes Ti6Al4V alloy occupy an important position in the military industry and people’s livelihood.However,as an important structural material,the poor wear resistance of Ti6Al4V alloy has become an important hidden problem during its service.Therefore,this paper investigates the wear behavior of Ti6Al4V alloy at different temperatures and uses solid carburizing to improve the hardness of the alloy and reduce the wear rate to achieve the effect of improving the wear resistance of Ti6Al4V alloy.The wear surface and carburized surface,element content and distribution,subsurface organization,phase composition,surface and cross-sectional hardness of the experimental samples were analyzed and measured using scanning electron microscopy,laser confocal microscopy,X-ray diffractometer,Zeiss optical microscope,and Vickers hardness tester.The dry sliding wear behavior of Ti6Al4V alloy was studied at a sliding speed of 1 m/s and at temperatures ranging from 20℃ to 400℃.It was found that the transition from mild wear to severe wear occurred in all wear processes at temperatures from 20℃to 350℃.The main wear mechanisms in the mild wear process include abrasive wear,delamination wear,adhesive wear and mild plastic deformation,and the severe wear process mainly includes severe plastic deformation and adhesive wear.The reason that the mild-severe wear transition did not occur at 400℃is that a mechanically mixed layer containing multiple oxide phases（Fe Al Ti O₅ and Fe Ti O₃）formed on the worn surface,preventing the occurrence of the mild-severe wear transition.Severe wear occurs because severe plastic deformation occurs on the wear surface,while dynamic recrystallization leads to softening of the wear surface inducing the occurrence of severe plastic deformation.In order to improve the wear properties of Ti6Al4V alloy at 20℃～350℃,the Ti6Al4V alloy was subjected to solid carburizing treatment.After the solid carburizing treatment,a TiC layer and a transition layer composed of Ti-Al compounds were formed at the carburizing interface,and both of them formed the total carburizing layer.The transition layer is formed at a low temperature and is formed preferentially during the solid carburizing process,and TiC is formed afterwards,where TiC will in turn inhibits the formation of the transition layer,and the relationship between the thickness of the two and the carburizing time is in accordance with the parabolic law.Less TiC is formed at 950℃and 1000℃with large transition layer thickness,and only a large amount of TiC is formed at 1050℃and 1100℃,but the transition layer thickness decreases slightly.The surface hardness and cross-sectional hardness are greatly increased after solid carburizing,both with the increase of carburizing time and/or the increase of carburizing temperature.Dry sliding wear tests were conducted on the carburized Ti6Al4V alloy,and even with a significantly increased experimental load,the overall wear rate was still much lower than that of the Ti6Al4V alloy before carburization,with no mild-severe wear transition and the wear surface in a slightly damaged state.The carburized Ti6Al4V alloy caused obvious damage to the abrasive disc material,resulting in a large amount of abrasive disc material being cut.Due to the material transfer,a large amount of Fe₂O₃and Ti O₂ oxides are formed on the wear surface,and the increase in hardness and the presence of the oxide layer play a significant role in protecting against Ti6Al4V wear.Abrasive wear and the rupture and peeling of oxide layer are the main wear mechanisms of Ti6Al4V alloy after carburization.Through the analysis,Ti6Al4V alloy will only have mild-severe wear transition at20℃～350℃,and the transition load is 20N～105N.The mild wear stage will cause slight damage to Ti6Al4V alloy,and the severe wear stage will cause great damage to the material.Improving the surface hardness of the alloy by solid carburizing can effectively enhance the wear resistance of Ti6Al4V alloy at 20℃～350℃and avoid the occurrence of severe wear,which makes Ti6Al4V alloy have excellent wear performance.