Tension‐tension fatigue performance of a SiC/SiC composite with an ytterbium‐disilicate environmental barrier coating (EBC) was investigated at 1200°C in air and steam. The composite is reinforced with Hi‐Nicalon™ SiC fibers and has a melt‐infiltrated matrix processed by chemical vapor infiltration of SiC with subsequent infiltration with SiC particulate slurry and molten silicon. The EBC consists of a Si bond coat and an Yb₂Si₂O₇ top coat applied via air plasma spraying. Tensile properties were evaluated at 1200°C. Tension‐tension fatigue was examined for maximum stresses of 110‐140 MPa. To assess the efficacy of EBC, experimental results obtained for the coated composite are compared to those for a control uncoated composite. Surface grit‐blasting inherent in the EBC application process degrades tensile strength of the composite. However, the EBC effectively protects the composite from oxidation embrittlement during cyclic loading in air or steam. Fatigue runout set to 200 000 cycles (55.6 hours at a frequency of 1.0 Hz) was achieved at 110 MPa in air and steam. Retained properties of pre‐fatigued specimens were characterized. Composite microstructure, along with damage and failure mechanisms were investigated. Damage and failure of the composite are attributed to the growth of cracks originating from numerous processing defects in the composite interior.

中文翻译：

---

高温下具有二硅酸environmental环境屏障涂层的SiC / SiC陶瓷复合材料的疲劳*

在1200°C的空气和蒸汽中研究了带有二硅酸environmental环境屏障涂层（EBC）的SiC / SiC复合材料的拉伸疲劳性能。该复合材料采用Hi‐Nicalon™SiC纤维增强，并具有通过化学气相渗透SiC以及随后的SiC颗粒浆料和熔融硅渗透处理的熔体渗透基体。EBC由一个硅键合涂层和一个Yb ₂ Si ₂ O _7组成。通过空气等离子喷涂的面漆。在1200℃下评价拉伸性能。检查了拉应力疲劳的最大应力为110-140 MPa。为了评估EBC的功效，将涂覆复合材料获得的实验结果与对照未涂覆复合材料的结果进行了比较。EBC应用过程中固有的表面喷砂处理会降低复合材料的拉伸强度。但是，EBC有效地保护了复合材料，使其在空气或蒸汽循环加载过程中不会发生氧化脆化。在110 MPa的空气和蒸汽中，疲劳跳动设定为200 000个周期（在1.0 Hz的频率下为55.6小时）。表征了预疲劳样品的保留特性。研究了复合材料的微观结构，以及破坏和破坏机理。