表面取向对IC-6合金高温氧化的影响

EFFECT OF SURFACE ORIENTATION ON OXIDATION BEHAVIOR OF DIRECTIONALLY SOLIDIFIED IC-6 ALLOY

采用TGA、EDAX及XRD等研究了定向凝固IC-6合金表面取向对其等温、循环氧化行为的影响.发现平行于凝固方向的纵切样品在950℃及1050℃下经100小时的等温氧化速率均明显大于横切样品的.这与横切样品表面存在品界,有利于铝的短路扩散有关。相反,由于Al_2O_3膜比较容易剥落,使横切样品表面在950℃抗循环氧化能力比纵切样品的差。在1100℃,晶界短路扩散作用减弱,横切与纵切样品循环氧化行为都表现出灾难性失重现象。

Effects of surface orientation on the isothermal and cyclic oxidation behavior of directionally solidified IC-6 alloy were studied by means of TGA, SEM/EDAX and SEM/EPMA. The longitudinal specimens are less resistant than transverse specimens with respect to isothermal oxidation at 950℃ and 1050℃ for 100 hours. It is claimed that grain boundaries intersecting the surface of transverse specimen facilitate short cut diffusion of Al atoms in the substrate to assist Al2O3 nucleation and growth on the surface. On the contrary, transverse specimens show poor cyclic oxidation resistance in comparison with longitudinal specimens due to the easiness of Al2O3 spallation upon temperature fluctuation. The contribution of lattice diffusion grows with temperature so that both specimens have the same disastrous weight loss rate when cyclically oxidized at 1100℃.