Research On High Temperature Oxidation Properties Of Modified Layer On γ-TiAl Alloy

Compared with the traditional super alloys, γ-TiAl alloy has been commonly recognized as themost promising high-temperature structural materials, owing to its low density, high specific strengthand high elastic modulus. With the effectively improvement of room temperature ductility,insufficient oxidation resistance above800℃was urgently needed to overcome. In this paper, thesurface modified aluminide layer on γ-TiAl alloy had been prepared by using powder packingcementation method and multi-arc ion plating technique. The microstructure, composition andcomposing phases of the alloyed layer were tested and analyzed. The mechanical properties, thermalshock resistance and high-temperature oxidation behaviors were tested and evaluated, respectively.The experimental results show that: the surface modified aluminide layers which are preparedin the two different processes had uniform thickness, low surface roughness and good thermal shockresistance. After oxidation at850℃in static air for100h，two modified layers both generated acontinuous and dense oxide film composed of Al₂O₃and effectively improved the γ-TiAl alloys850℃oxidation resistance. The sample treated by packing cementation aluminized had a thin oxide filmcomposed of Al₂O₃and a small amount of TiO₂after high temperature oxidation at950℃in air for100h. The oxide film was only4μm and improved the γ-TiAl alloys850℃oxidation resistance. Thesample treated by multi-arc ion plating multi-arc ion plating aluminium had a thicker oxide filmwhich was15μm and composed of Al₂O₃and TiO₂after oxidation at950℃in static air for100h.There were a large number of pores in the oxide film. Cyclic oxidation tests at900℃showed that themodified aluminide layer by pack cementation technique could effectively improved the γ-TiAl alloys900℃cyclic oxidation resistance. But, there was a significant peeling the films from the substrate ofthe sample treated by multi-arc ion plating aluminium after the cyclic oxidation experiments carried87times at900℃. It shows that the improvement of γ-TiAl alloys900℃cyclic oxidation resistanceof the modified alminide layer by multi-arc ion plating was not so significant as that through usingpowder packing cementation method.