In the current study, the low carbon Ni-based superalloy Inconel-738 (IN-738LC) was used as the substrate and a metallic bond coat (NiCrAlY) was deposited on the substrate by air plasma spray (APS) method. Subsequently, the layer was coated by a ceramic interlayer Yttria-stabilized zirconia (YSZ) by APS. Finally, as the last ceramic layer, a hybrid ceramic top layer containing mullite and YSZ was plasma deposited on the YSZ interlayer in various compositions such as: 25 wt% mullite/75 wt% YSZ, 50 wt% mullite/50 wt% YSZ, 75 wt% mullite/25 wt% YSZ, and 100 wt% mullite. In order to investigate the oxidation resistance of the produced TBCs, they were heated at 1000 °C for 50 and 100 h. The results showed that the presence of mullite phase is advantageous to hybrid coatings, so that in the 50 wt% mullite/50 wt% YSZ hybrid coating, the percentage of destructive spinel oxides forming the thermally grown oxide (TGO) layer reduced compared to the 25 wt% mullite/75 wt% YSZ coating. Moreover, aluminum oxide is the dominant oxide in the 50 wt% mullite/50 wt% YSZ hybrid coating. However, the further increase in the mullite percentage had no noticeable effect on the reduction of spinel oxides. In addition, the presence of mullite alongside YSZ led to an increase in the hardness of the 25 wt% mullite/75 wt% YSZ hybrid coating (845 HV) compared to the conventional coating including a YSZ layer (680 HV) or a mullite layer (655 HV). The X-ray diffraction (XRD) analysis revealed that the presence of mullite beside YSZ in the coating increases the stability of the coating after oxidation test so that, in the XRD pattern, monoclinic phase was not detected in the hybrid coatings. In general, 50 wt% mullite/50 wt% YSZ hybrid coating provided the best results compared to other coatings. Moreover, with increasing thickness of the hybrid ceramic layer containing 50 wt% mullite to 350 μm, the thickness of the TGO layer decreased to approximately 7 μm. Additionally, it was shown that due to the decrease of chromium and nickel elements in the TGO layer, the level of the spinel oxides in the thick coatings decreases. This led to an increase in the stability of the TGO layer and an extension of the thermal system's lifespan.

中文翻译：

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IN-738LC 上等离子喷涂莫来石/YSZ 混合热障涂层：微观结构、相分析和抗氧化性

本研究以低碳镍基高温合金Inconel-738（IN-738LC）为基体，采用空气等离子喷涂（APS）方法在基体上沉积金属结合层（NiCrAlY）。随后，通过 APS 在该层上涂覆氧化钇稳定氧化锆 (YSZ) 陶瓷夹层。最后，作为最后一个陶瓷层，将含有莫来石和 YSZ 的混合陶瓷顶层以各种组成等离子沉积在 YSZ 夹层上，例如：25 wt%莫来石/75 wt% YSZ、50 wt%莫来石/50 wt% YSZ、 75 wt% 莫来石/25 wt% YSZ 和 100 wt% 莫来石。为了研究所生产的TBC的抗氧化性，将它们在1000℃下加热50和100小时。结果表明，莫来石相的存在有利于混合涂层，因此在50 wt%莫来石/50 wt% YSZ混合涂层中，形成热生长氧化物（TGO）层的破坏性尖晶石氧化物的百分比比25 wt% 莫来石/75 wt% YSZ 涂层。此外，氧化铝是 50 wt% 莫来石/50 wt% YSZ 混合涂层中的主要氧化物。然而，莫来石百分比的进一步增加对尖晶石氧化物的还原没有明显影响。此外，与包含 YSZ 层 (680 HV) 或莫来石层的传统涂层相比，莫来石与 YSZ 一起存在导致 25 wt% 莫来石/75 wt% YSZ 混合涂层 (845 HV) 的硬度增加（655 高压）。 X射线衍射（XRD）分析表明，涂层中除了YSZ之外还存在莫来石，这增加了氧化测试后涂层的稳定性，因此在XRD图谱中，在杂化涂层中没有检测到单斜晶相。一般来说，与其他涂料相比，50 wt% 莫来石/50 wt% YSZ 混合涂料提供了最佳结果。此外，随着含有50wt％莫来石的混合陶瓷层的厚度增加至350μm，TGO层的厚度减小至约7μm。此外，结果表明，由于TGO层中铬和镍元素的减少，厚涂层中尖晶石氧化物的水平降低。这提高了 TGO 层的稳定性并延长了热系统的使用寿命。