Fundamental Research On MEVVA Ion Implantation For Anti-Fatigue Manufacture Of Titanium Alloy

In recent years, MEVVA ion implantation has been intensely developed for surface modification of materials. On the other hand, it is important to improve fretting damage resistance of titanium alloy in aeronautic industry and other fields. By using of the MEVVA ion implantation method, experimental studies of the failure mechanism and control technology of fretting damage were carried out in present dissertation. The research work can be summarized as follows:The surface roughness parameters were measured for TC4 titanium alloy with and without metallic ion implantation. The results showed that La or Mo ion implantation leads to reduction of the values of the amplitude parameters of the surface roughness remarkably. The microhardness was improved. Mo ion implantation improved corrosion resistance of TC4 alloy in acidic chloride solution, but La ion implantation gave opposite result because they have different chemical activity.The plain fatigue experiment showed that La or Mo ion implantation improved fatigue performance of TC4 alloy. The reasons were that ion implantation strengthened surface layer, which reduced probability that cracks originated from surface. The features of titanium alloy fatigue fracture were studied by means of observing fatigue fracture appearance.La or Mo ion implantation reduced the fretting wear of TC4 alloy very greatly under both line contact and point contact conditions. The friction coefficient of ion implanted specimens was less than that of unimplanted specimens at initial stages of fretting wear, but ion implantation hadn't influence during stable wear stages. The damage mechanism of titanium alloy was abrasive wear and contact fatigue during fretting wear.The fretting fatigue life could be improved by 20% and the friction coefficient be decreased by 13~20% after La or Mo ion implantation. The damage mechanism of fretting fatigue was abrasive wear and fatigue delamination. Based on the experiment results, a model for the mechanism of fretting fatigue damage and the evolving procedure of fretting debris were given, and the role of debris during fretting damage was analyzed. Fretting maps were introduced to describe influence of MEVVA ion implantation on fretting fatigue behavior of titanium alloy.