Abstract: 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 Al2O3 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.
Thermal cyclic oxidation behavior of NiCoCrAlYHf/EB-PVD TBCs
Abstract:
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 Al2O3 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.
定向凝固的Ni3Al基高温合金的名义成分为(质量分数, %): Cr 5.0~7.0、 Ta 0~2.0、 Al 6.5~8.0、 Ti 1.0~4.0、 W 1.0~3.0、 Mo 3.0~5.0、 Ni余量。 采用阴极电弧镀法表面沉积MCrAlYHf抗氧化粘结涂层的名义成分(质量分数, %): Cr 18.0~23.0、 Co 10.0~15.0、 Al 8.0~12.0、 Y 0.1~0.5、 Hf 0.2~0.6、 Ni余量。 Ni3Al基高温合金基底试样的尺寸为10 mm×30 mm×2 mm, NiCoCrAlYHf粘结层厚度约为60 μm。 涂覆粘结层后的试样在1 000 ℃真空热处理2 h, 然后用电子束物理气相沉积厚80~90 μm的8% Y2O3部分稳定的ZrO2陶瓷热障层。
图1 NiCoCrAlYHf/EB-PVD TBCs的 循环氧化动力学曲线 Fig.1 Cyclic oxidation kinetic curve of NiCoCrAlYHf/EB-PVD TBCs heated at 1 100 ℃ for 30 min, cooled at 25 ℃ for 5 min
图2 失效TBCs 样品的宏观像 Fig.2 Macroscopic photograph of failed TBC specimen