Effect of Cryogenic Treatment on Microstructure and Tribological Property Evolution of Electron Beam Melted Ti6Al4V

Cryogenic treatment was used to improve the tribological properties of Ti6Al4V artificial hip joint implants.Cryogenic treatment at-196 ℃ with different holding time were carried out on Ti6Al4V specimens fabricated using electron beam melting (EBM),and their microstructure and tribological properties evolution were systematically analyzed by scanning electron microscopy (SEM),vickers hardness,and wear tests.The experimental results show that the as-fabricated specimen consists of lamellar α phase and β columnar crystal.While,the thickness of lamellar α phase decreased after cryogenic treatment.In addition,it can be found that the fine α phase was precipitated and dispersed between the lamellar α phase with the holding time increase.Vickers hardness shows a trend of first increasing and then decreasing.The wear rate of the specimen cryogenic treated for 24 h is the minimum and the average friction coefficient is 0.50,which is reduced by 14.61% compared with the as-fabricated.The wear mechanism of the as-fabricated specimen is severe exfoliation,adhesive,abrasive,and slight fatigue wear.However,the specimen cryogenic treated for 24 h shows slight adhesive and abrasive wear.It can be concluded that it is feasibility of utilizing cryogenic treatment to reduce the wear of EBMed Ti6Al4V.