Low-Cost Molybdenum Disilicide Matrix Composites

碳纤维增强碳化硅晶须增强二硅化钼(MoSi2)基复合材料已被认为是氧化环境中高温结构应用的极佳候选材料。然而，这些材料的室温断裂韧性、高温屈服和蠕变强度仍有很大提高，加工问题必须解决。在这个第一阶段的提案中，UltraMet建议证明几种MoSi2基复合材料制造方法的可行性，这些方法能够消除主要的加工缺陷来源，并在提高机械性能的同时大大提高工艺的重复性和成本效益。采用化学气相沉积法(CVD)制备了具有多种合金组织的MoSi2涂层晶须和MoSi2渗透碳布，并对其进行了性能测试。这些结果将与SiC/MoSi2、C/C和C/SiC材料的现有数据进行比较，并将对成本、可靠性、可制造性和性能进行分析。MoSi2复合材料最直接的应用是发动机热段部件和工业窑炉设备，这是另一个潜在的市场。此外，随着环保局即将提出的大幅减少排放的要求，将需要更多的新材料，如MoSi2，以承受与清洁燃烧、低NOx技术相关的更高温度。

Carbon fiber-reinforced in SiC whisker-reinforced molybdenum disilicide (MoSi2) matrix composites have been identified as excellent candidates for high temperature structural applications in oxidizing environments. However, the room temperature fracture toughness and high temperature yield and creep strength of these materials can still be drastically improved, and processing issues must be resolved. In this Phase I proposal, Ultramet proposes to demonstrate the feasibility of several fabrication methods for MoSi2 matrix composites that are capable of eliminating the major sources of processing flaws and of greatly increasing process repeatability and cost-effectiveness, while enhancing mechanical properties. MoSi2-coated whiskers and MoSi2-infiltrated carbon fabric will be fabricated by chemical vapor deposition (CVD) with several alloy microstructures, followed by properties measurements. These results will be compared to available data for SiC/MoSi2, C/C, and C/SiC materials, and an analysis of cost, reliability, fabricability, and performance will be conducted. The most immediate application for MoSi2 composites for engine hot section components, and industrial furnace equipment is another potential market. Also, with upcoming EPA requirements for drastically reduced emissions, new materials such as MoSi2 will be required in much greater quantities to withstand the higher temperatures associated with clean-burning, low-Nox technology.