反应溅射氧化铝薄膜对CoCrAlY涂层抗高温氧化性能的影响

EFFECT OF REACTIVELY SPUTTERED ALUMINA FILM ON OXIDATION RESISTANCE OF CoCrAlY COATING

研究了反应溅射氧化铝薄膜对CO-30Cr-6Al-0.5Y涂层抗高温氧化性能的影响。结果表明,3.5μm厚的Al_2O_3薄膜可大大改善CoCrAlY涂层抗1000～1100℃的氧化性能。在1000℃下,C0-30Cr-6Al-0.5Y涂层表面可以形成保护性良好的Al_2O_3膜,在此情况下,反应溅射Al_2O_3膜可大幅度降低CoCrAlY涂层的氧化速率,在1100℃,CoCrAlY涂层己不能形成单一具有保护性的Al_2O_3膜,而预先沉积氧化铝薄膜的COCrAlY涂层表面的氧化物主要由α-Al_2O_3组成,从而使CoCrAlY涂层的抗氧化性能大大提高。

Thin alumina films have found applications in electronic circuits and cutting tools. Recently, these films have been explored as protective coatings against high temperature oxidation, but only a few papers were devoted to the subject.In this study, the amorphous alumina films of 3.5μm on the Co-30Cr-6Al-0.5Y coatings were produced by reactive sputtering, using a pure aluminum target in Ar+O_2atomsphere. The isothermal oxidation tests were carried out at 1000-1100℃ in static air. The results showed that the alumina films improved oxidation resistance at all testing temperatures. At 1000℃, the Co-30Cr-6Al-0.5Y coating could form pure alumina scale on its surface. In this case, the reactively sputtered alumina films reduced the oxidation rate. At 1100℃, the Co-30Cr-6Al-0.5Y coating could not form pure alumina scale, as the result of severe internal oxidation of aluminum along columnar defects. The scales were composed of Al_2O_3, Cr_2O_3and TiO_2, which were not so protective as pure alumina scale. On the contrary, the Co-30Cr-6Al-0.5Y coatings with 3.5μm pre-deposited alumina films exhibited excellent oxidation resistance at 1100℃. Only a minor amount of TiO_2was detected on it's top surface. Moreover, the reactively sputtered alumina films were very adherent to the CoCrAlY coatings. At 1000℃, no spallation was found, while at 1100℃, only a little spallation was observed which was proved to occur durring cooling.