液相渗Si提高TiAl基合金的高温抗氧化性

使用液相Al—Si合金对TiAl基合金进行表面渗Si处理，可明显增强TiAl基合金的高温抗氧化性．经1273K，100h的恒温氧化后，不同的表面涂层使合金在40—100h之间的氧化速率降低了2个数量级，恒温氧化100h后的最终氧化皮脱落量也减少3个数量级．液相渗Si使TiAl基合金表面高温抗氧化性能得到大幅度改善，其根本原因是Si与TiAl中的元素Ti结合，降低了Ti的活度，相对增强了涂层中元素Al的活度，而且涂层中Al的绝对含量也得到明显提高，这些均抑制了高温氧化过程中TiO2的生成，涂层最外层形成了致密的Al2O3氧化膜．

Improvement of High Temperature Oxidation Resistance of TiAl-Based Alloy by Liquid Phase Siliconization

The high temperature oxidation resistance of the TiAl-based alloy can be obviously improved by liquid phase siliconization through the Al-Si alloy. Compared with the bare TiAl-based alloy, the oxidation rate for the duration from 40 h to 100 h of the coated TiAl alloys is decreased for 2 order of magnitude, and the amount of the dropped oxides is also reduced for 3 order of magnitude. The main reason of the improvement of the oxidation resistance is the combination of Si in the Al-Si alloy with Ti in the TiAl alloy, resulting in the decrease of the activity of Ti, and therefore relatively, the increase of the activity of Al in the surface layer of the TiAl alloy. Furthermore, the concentration of element Al in the coating is remarkably increased. Therefore, during the isothermal oxidation of the coated TiAl alloy, the formation of TiO2 is inhibited, and the compacted oxide film of Al2O3 is preferentially formed on the coating surface of the TiAl alloy.