Study Of Preparation And Performance Of High-frequency Induction Intriding Layer On Titanium Alloy

Titanium alloy as a new structural and functional material is progressively used in so many new and high technology fields of aerospace, petroleum, atomic energy, shipping, surgery implant and so on, because it has a series of excellent properties, such as high specific strength, low density, thermal stability, corrosion resistance, fatigue resistance, biologic compatible etc . But titanium alloy appears poor wearing resistance, easily conglutinating by heated, reduction of plasticity and strength as a result of fish tail and engage in the surface of alloy. When the temperature >550℃,oxidation coating formed in the surface can be absorbed by the Ti and will being strongly chemical reaction with the air ,resulted in hydrogen brittle crack. The application of titanium alloy can be restricted because of these shortcomings. Therefore, it is very important that titanium alloy should be surface-treated in order to improve the performances in use.In the thesis, High-frequency induction nitriding was applied on preparing the nitride layers on the surface of TC4 titanium alloy. The high-frequency induction nitrding is a new technique on the surface of titanium alloy in comparing to other surface treatment techniques due to its low energy cost, high efficiency, and good work environment. The relevant processing parameters including treading temperature and time were mainly studied. The factors on performances of nitridng layers were analyzed. Then, microstructure and phase composition were researched by SEM and XRD. At last, forming mechanism of nitriding layers was also elementarily discussed.The processing parameters related with the high-frequency induction nitrding have been obtained by study. And some laws as follows: (1)relation between different treading temperatures and the nitriding layer's performances; (2)relation between different treading times and the nitriding layer's performances; It is shown that the oxidation layers are mainly composed of TiN and Ti2N from XRD and XPS. The thickness of layer is 22.8—32.8μm, and the hardness is HV 500～1319.In comparing to micro-plasma nitriding, the high-frequency induction nitriding technique has the shortest treating time and the highest efficiency, and the performances of nitriding layer obtained by high-frequency induction nitriding is much better, and it can not lead to environment polluted. Therefore, the high-frequency induction oxidation is promising technique in surface treating of titanium alloy.