TiAl合金具有质量轻、强度高、耐腐蚀的出色性能，是航空发动机的关键结构材料，其硬度和抗高温氧化性能需要进一步提高。本论文主要通过阴极和阳极液相放电技术，分别在TiAl合金表面制备出致密的氧化膜，对膜层制备过程进行分析，探究膜层的生长机理，并对生长出的氧化膜层的组织性能进行评估。

首先利用阴极等离子体电解氧化（CPEO）技术在甘油水溶液中放电2 - 8 min,获得厚度为10 - 35μm的氧化膜。膜厚随着电压的增加和放电时间的延长而增加，但膜层表面残留孔洞增多，火花冲击痕迹明显。同时氧化膜的表面粗糙度也增加到6.932μm，显微硬度提高到750 HV以上。CPEO表面处理改变了TiAl合金的浸润性，由亲水性变为疏水性，同水的接触角增加到115 °。氧化膜由Al₂TiO₅复合氧化物、锐钛矿相、金红石相以及α- Al₂O₃相组成。

根据CPEO放电过程中探测的发射光谱，计算出等离子体放电区的电子浓度为4.8*10²² -5.6*10²² m^-3，达到局部热平衡状态。利用特征峰强度计算出电子温度平均为5500 K左右。研究发现，噪声与振动信号诊断是探索CPEO放电机理及氧化膜生长机制的有效方法。

此外，在硅酸钠电解液中，通过阳极等离子体电解氧化即微弧氧化技术(MAO)在TiAl合金表面制备出厚度 30 μm的陶瓷氧化膜，并率先测试了TiAl合金基体和微弧氧化膜在900 - 1200 ℃的蒸汽氧化行为。发现不同温度条件下，微弧氧化膜均表现出优于TiAl合金基体的抗高温蒸汽氧化性能，氧化增重只有合金基体的55 - 80%，微弧氧化表面处理是提高TiAl合金抗蒸汽氧化能力的有效方法。蒸汽氧化后TiAl合金基体从外向内依次是TiO₂晶粒层-TiO₂和Al₂O₃的混合氧化物层-贫铝层氧化形成的钛铝氧化物与Ti₃Al的交互层-Ti₃Al贫铝层-TiAl合金基体。MAO处理的TiAl合金从外向内依次是初始微弧氧化层TiO₂和Al₂O₃的混合氧化物层-钛铝氧化物与Ti₃Al的交互层-TiAl合金基体。在高温环境中，Ti、Al、Si的亚稳态氧化物均会转化为更加稳定的相，锐钛矿相转化成稳定的金红石相，γ-Al₂O₃相转化成稳定的α-Al₂O₃相，而非晶态的SiO₂晶化为方英石相。

TiAl alloy has excellent properties of light weight, high strength and corrosion resistance. It is one of key structural materials of aero-engine, its hardness and high temperature oxidation performance need to be further improved. In this paper, the cathode and anode liquid discharge techniques were used to prepare a dense oxide film on TiAl alloy. The fabrication process of the films was analyzed, the growth mechanism of the films was explored, and the microstructure and properties of the oxide films were evaluated.

Firstly, cathode plasma electrolytic oxidation (CPEO) technique was used to to obtain oxide films with thickness of 10-35 μm after 2-8 min discharge in glycerol aqueous solution. The film thickness increases with the increase of applied voltage and discharge time, but the remained pores on the film surface increase, and the spark impact trace is obvious. The surface roughness of the oxide film increases to 6.932 μm, and the microhardness is up to 750 HV. In addition, it is found that CPEO surface treatment changes the wettability of TiAl alloy from hydrophilic to hydrophobic, and the contact angle with water increases to 115 °. The oxide film is composed of Al₂TiO₅ composite oxide, anatase phase, rutile phase and α-Al₂O₃ phase.

According to the emission spectrum detected in the discharge process of CPEO, the electron concentration in the plasma discharge area is calculated to be 4.8* 10²²-5.6 *10²² m^-3, so the local thermal equilibrium in discharge channel is reached. The average electron temperature is calculated to be about 5500 K on basis of the characteristic peak strength.It is found that the diagnosis of noise and vibration signals is an effective method to explore the discharge mechanism of CPEO and the growth mechanism of oxide film.

In addition, a ceramic oxide film of 30 μm thick is prepared on TiAl alloy by micro-arc oxidation (MAO) technique in sodium silicate electrolyte. The vapor oxidation behavior of bare and MAO coated TiAl alloy at 900 ~ 1200 ℃ was firstly tested. It is found that at different temperatures, the high temperature steam oxidation resistance of micro-arc oxidation film is better than that of bare TiAl alloy, and the oxidation weight gain of oxidation film is only 55-80% of that of the alloy matrix. Micro-arc oxidation surface treatment is an effective method to improve the vapor oxidation resistance of TiAl alloy. The MAO surface treatment is an effective technique to improve the steam oxidation resistance of Zr alloys. After steam oxidation, from the outer surface to the alloy substrate, the bare TiAl alloy includes a TiO₂ grain layer, a mixed oxide layer of TiO₂ and Al₂O₃ , an interaction layer of Ti-Al oxide in Ti₃Al matrix, a Al-depleted Ti₃Al alloy and TiAl alloy substrate. However, after steam oxidation, the MAO coated TiAl alloy includes an initial micro-arc oxide layer, a TiO₂ and Al₂O₃ mixed oxide layer , Ti-Al oxide and Ti₃Al interaction layer and TiAl alloy substrate. In the high temperature environment, the metastable oxide phase of Ti, Al and Si will be transformed into a stable phase. Aanatase phase will be transformed into stable rutile phase, γ-Al₂O₃ phase will be transformed into stable α-Al₂O₃ phase, and amorphous SiO₂ will be crystallized into cristobalite phase.