NiCoCrAlYHf/EB-PVD热障涂层的热循环氧化行为

Thermal cyclic oxidation behavior of NiCoCrAlYHf/EB-PVD TBCs

采用电子束物理气相沉积方法(EB PVD)在NiCoCrAlYHf粘结层上沉积YSZ热障层,研究了该热障涂层1100℃的循环氧化行为(每个循环为:1100℃保温30min、空冷5min),分析了粘结层和热生长氧化物的演化过程。结果表明:NiCoCrAlYHf粘结层氧化初期由β NiAl和γ固溶体组成,186次循环氧化后β相完全转变为γ固溶体。NiCoCrAlYHf/EB PVD热障涂层中的热生长氧化物包含Al2O3层和靠近热障层的尖晶石薄层。该热生长氧化物生长速度较快,在粘结层的一些富Hf区域优先生长而呈现出明显的不均匀性;但其具有较大的失效临界热生长氧化物厚度,失效时热生长氧化物均匀处的厚度约为10μm。

The cyclic oxidation(30 min hold at 1 100 ℃, 5 min cooled in air) of electron beam physical vapor deposition(EB-PVD) yttria stabilized zirconia thermal barrier coatings(TBCs) on NiCoCrAlYHf bond coat at 1 100 ℃ was investigated. Attention was focused on the development of bond coat and thermally grown oxide(TGO). The result shows that the bond coat is composed of β -NiAl and γ solid solution at the initial stage of cyclic oxidation. The β phase is completely transferred to γ solid solution after 186 cycles. The TGO consists of an Al_2O_3 layer and a thin spinel layer in NiCoCrAlYHf/EB-PVD TBCs. This TGO has a big growth rate and grows irregularly because of selective growth at Hf-riched areas in the bond coat. But the TBCs has a larger critical thickness of TGO for failure. The thickness of TGO at uniform place is about 10 μm when the TBCs fails.