钛合金微弧氧化陶瓷膜层高温氧化机制研究

Micro-arc oxidation is a technique used for the in situ formation of a ceramic coating on the surface of valve metal via plasma discharging. Studies on pretreatment of titanic alloys and post-processing treatment after micro-arc oxidation have been rarely reported. No study on the mechanism of high-temperature oxidation of ceramic coatings obtained through a micro-arc process has been found. This project focuses on the pretreatment of the nanonization process of the titanic alloy surface, the sealing treatment after micro-arc oxidation of ceramic coatings, and the improvement of the compactness of the coatings via calcination under argon atmosphere. Restrained micro-arc oxidation of the coatings will be realized by controlling the spark discharging process. A complete evaluating system for the high-temperature oxidation resistance of coating materials will be established. The high-temperature oxidation resistance of the coating materials around their application temperature will be emphasized. Problems such as surface corrosion during the high-temperature application process, weight increases as a result of high-temperature oxidation, and mechanical performance degradation of the coating materials will be focused. The ultimate goal of this project is to prepare ceramic coatings with high-temperature oxidation resisting properties. In the mean time, the mechanism of high-temperature oxidation of the coating materials will be studied as well. Through this study, there is a potential to speed up the practical application of titanic alloys.

微弧氧化通常指在阀金属（铝、钛、镁等）表面进行等离子体放电原位生长陶瓷膜的一种表面处理技术。目前该项技术在膜层制备方面的工艺研究已较为成熟，但在对基体合金的预处理及所生成陶瓷膜层的后处理技术方面研究的报导甚少，尤其是在微弧氧化陶瓷膜层高温氧化机制方面的深入研究更是未见报导。本项目主要通过对基体钛合金进行表面纳米化预处理后进行微弧氧化，从而达到提高膜层与基体合金间结合力的目的。通过有效地控制火花放电实现抑弧氧化来进一步提高膜层致密性。本项目的研究重点在于，通过将制得的膜层分别放在空气和氩气中焙烧后，根据膜层组分及元素价态的变化规律，对钛合金微弧氧化陶瓷膜层高温氧化的机制进行深入而系统的研究，进而提高钛合金在实际中的应用。

利用双极微弧氧化电源来制备钛合金表面陶瓷膜层，研究其抗高温性能和高温反应机制。与通常的微弧氧化反应相比，双极微弧氧化反应中二个电极上的反应均可进行微弧氧化反应。其中一个反应试样接电源的阳极，另一个反应试样接阴极。由于双脉冲反应阴阳极是交替进行的，因此当一个试样进行反应时另一个试样暂做阴极，这样两个试样便都可生成陶瓷膜。在硅酸盐体系下，其他条件一定时，只改变占空比的情况下，生成了主要晶相为TiO2的陶瓷膜层。其他条件恒定，只改变占空比，通过微弧氧化所制的的陶瓷膜层，其表面的孔隙数量与占空比相关。占空比越低，膜层表面孔隙数量越少。经高温氧化测试，所制的膜层高温氧化增重量低，与基体和其他膜层相比，抗高温氧化性能明显提高。我校与哈工大已联合研制出双电极微弧氧化电源，除能在双相电压提供双级，还可以具有六种反应波形，其中两种为新波形。与常规的微弧氧化不同，两个电极均是反应电极，利用该特殊微弧氧化方法制得的膜层进行高温氧化研究，是本研究的特色所在。