Oxidation of intermetallics - Japanese activity

Oxidation studies on intermetallic compounds carried out in Japan in the last ten years have been summarized and critically reviewed. The major effort was expended to improve the oxidation resistance of TiAl-base materials. The methods tried include alloying additions, surface treatments and combinations of the both. Alloying additions to TiAl were more closely reviewed here. An excellent oxidation resistance was obtained owing to the formation of Al2O3 scales by alloying additions of 0.2Zr, 0.2Hf or 500 ppm Cl, and by Nb-ion implantation. Preoxidation under reduced oxygen pressures also resulted in the formation of protective Al2O3 scales. Ceramic coatings and MCrAlY-type coatings showed some improvement in the oxidation resistance. Studies on other aluminides of current interest are relatively few. On the other hand, studies on silicides are becoming more active than before, though still few in comparison with TiAl-base materials. In the concluding remarks directions for future studies are shown.