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4735 |
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Wednesday, May 11, 2016, Yellow River Hall 4:00 PM Aviation Industry III |
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Isothermal and cyclic oxidation of cold sprayed NiCoCrAlTaY coating on CMSX-4 superalloys |
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Deliang Guo / University of Ottawa, Canada Bertrand Jodoin / University of Ottawa, Canada Linruo Zhao/ National Research Council Canada, Canada Mohammed Yandouzi/ University of Ottawa, Canada Mohammed Yandouzi/ University of Ottawa, Canada Rubén Fernández*/ University of Ottawa, Canada |
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Cold gas dynamic spraying (CGDS or cold spray) has been proven a promising manufacturing process for deposition of MCrAlY coatings for gas turbine applications. A commercial MCrAlY powder (NiCoCrAlTaY) was deposited on a Ni-base single crystal superalloy (CMSX-4) using the cold spray technology with nitrogen as both the processing and carrying gas. A dense coating (porosity < 0.5%) was achieved after optimized spraying parameters within the studied range. Isothermal and cyclic oxidation tests were carried out at 1100°C up to 500 h and 1500 cycles, respectively. The evolution of morphology, microstructure and phase composition of the coating-substrate system was characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) techniques. Results show that a continuous thermally grown oxide (TGO) layer composing of ±-Al2O3 is formed right after oxidation (1h for isothermal testing, 1 cycle for cyclic testing) at 1100°C without the presence of any other types of Al2O3. A ²-phase depletion zone was observed near both the top regions of the MCrAlY coatings due to the formation of ±-Al2O3 TGO, and the bottom regions due to the inter-diffusion between coatings and substrates, which essentially accelerates the consumption of ² phase. Nevertheless, it seems that the presence of aluminum in the matrix (³ phase) of the coatings is sufficient to maintain the TGO in the form of ±-Al2O3 in spite of the ²-phase depletion throughout the coatings. The normally observed spinel oxides after ²-phase depletion were barely seen even after the longest oxidation duration/cycles in this study. Keyword: cold spray, MCrAlY coating, CMSX-4, isothermal oxidation, cyclic oxidation |