TiAl合金高温循环氧化行为及其表面改性研究

研究了TiAl金属间化合物及表面涂层在空气中的高温循环氧化行为。结果表明:在800℃时TiAl合金具有较好的抗高温氧化行为,但当温度高于800℃时,TiAl合金表面未能形成单一的Al2O3保护层,而是形成外3层为疏松的TiO2层,内层为TiO2+Al2O3的混合氧化物层,因而使得TiAl合金的抗高温循环氧化性能严重蜕化。TiAl合金经过Cr改性铝化处理后,表面形成了具有立方Ll2结构的Al67Ti26Cr7层,立方Ll2结构的Al67Ti26Cr7不仅具有较高的铝含量,而且具有优良的韧性,因而使得处理后的TiAl合金具有良好的抗高温循环氧化性能。铝化物涂层尽管有很高的铝含量,但由于铝化得到的TiAl3相具有四方形结构,涂层非常脆,故该涂层抗高温循环氧化性能有待进一步提高。

CYCLIC OXIDATION BEHAVIOR OF TiAl AND SURFACE MODIFICATION

The cyclic oxidation behavior of TiAl alloy in air was studied. The cyclic oxidation resistance of TiAl alloy is excellent up to 1073K, but beyond that three outer nodular TiO 2 layers and an inner layer with mixed TiO 2 and Al 2O 3 are formed. The cyclic oxidation resistance of TiAl alloy is improved by depositing Cr\|modified aluminide or alluminide coatings. The Cr\|modified aluminide coating exhibits excellent cyclic oxidation resistance due to formation of Al 67 Ti 26 Cr 7 layer with a ductile cubic Ll 2 structure. Aluminide coating has the tetragonal DO 22 structure which has low symmetry and offers poor ductility and toughness, resulting in an intermediate oxidation rate.