Effect Of Shot Peening And Hot Isostatic Pressing On Wide Temperature Range Tribological Properties Of Ti6Al4V Rolled Plate

Compared with other alloys,titanium and its alloys have unique physical and chemical properties,so they are widely used in aerospace,chemical,automotive and biomedical fields.However,in addition to the high economic cost in the preparation and machining process,the unsatisfactory tribological properties of titanium alloy are also the main reason limiting its further application.It is of great significance to explore a lower cost method for improving the tribological properties of titanium alloys.First of all,this paper uses shot peening technology to prepare the enhanced layer on the surface of Ti6Al4 V.First,through SEM observation of the changes in the microstructure of Ti6Al4 V surface before and after shot peening,it is found that the shot peening will make Ti6Al4 V surface grain fragmentation,thus forming fine crystals.The dimensional hardness test shows that the surface hardness of shot peening specimen increases with the hardening of fine grain.It is found that a mechanical mixing layer(MML)is formed on the surface of shot peening samples at high temperature to protect the worn surface.Wherein,MML is formed by the wear scraps and O of the substrate through mechanical mixing and sintering at high temperature.MML protects the substrate during the friction process,avoiding direct contact between the dual parts and the substrate and reducing the wear rate.Then,the effect of microcosmic internal strain on fatigue wear life of materials is studied for the first time.The internal strain of the material is eliminated by hot isostatic pressing.Based on microstructure analysis,it is found that the deformation structure of Ti6Al4 V matrix is almost transformed into substructure and recrystallized crystal by hot isostatic pressing treatment.The increase of grain size and the decrease of work hardening effect reduced the hardness of Ti6Al4V-HIP by about 10%.However,the reduction of internal strain inhibits the formation and propagation of cracks in the friction process,and thus inhibits the large area shedding in the friction shear process,resulting in a significant reduction in the size of worn fragments.Small size wear fragments will have a higher specific surface energy,which will accelerate the formation of high temperature oxidation friction layer,so that high temperature wear resistance is greatly reduced.Finally,the Ti6Al4 V surface hardening layer was prepared by combining hot isostatic pressing and shot peening.The microstructure of the hot isostatic press-shot peening samples was compared with that of other processing samples,and it was found that the grain breakage of hot isostatic press-shot peening samples was more obvious.It is found that the tribological properties of hot isostatic pressure-shot peening samples at high temperature are better than those of fine chips.The small wear fragments show high surface activity.In the friction process,it is easy to react with O to form Ti oxide,and also easier to sintering MML on the wear surface in the friction reciprocating shear process,so as to improve the high-temperature wear resistance.