富钼相网状分布改性二硅化钼涂层的制备及性能研究

Molybdenum disilicide (MoSi2) is expected to be used as a promising wear-resistant coating for engineering application. However, the inherent brittleness and poor interface strength of plasma spraying MoSi2 coating restrict its wide-range applications. In this project, MoSi2 spherical powder coated by rich molybdenum phases will be prepared with heterogeneous precipitation, thermal reduction, spray drying technology and vacuum singtering technology. In order to improve the mechanical proterties and wear resistance performance of MoSi2 coating, the new idea of brittleness and interface strength of MoSi2 coating improved using rich molybdenum phases network structure distribution was proposed. The influence of preparation technology on the rich molybdenum layer thickness, interface structure and microstructure were studied, and the formation mechanism of coating powder was also studied, aiming to realize the optimization control of powder preparation. The effects of rich molybdenum layer size, microstructure and interface microstructure on the mechanical performance and tribological performance of MoSi2 coating are examined. The relationship between microstructure,mechanical performance and tribological performance of MoSi2 coating was determined.The toughening mechanism and wear mechanism of MoSi2 coating modified using rich molybdenum phases network structure were revealed. The research results provide some useful theoretical support and experimental basis for development of high performance friction material. It is of great importance for enriching and developing the tribology theory and design.

二硅化钼（MoSi2）是一种极具应用潜力的耐磨涂层材料。然而，等离子喷涂MoSi2涂层的低韧性和弱结合强度制约着其实际应用。改变传统的材料组分研究思想，采用非均相沉淀-热还原-喷雾干燥-真空烧结技术制备富钼相网状分布MoSi2喷涂粉末，提出利用富钼相网状分布来改性MoSi2涂层的新思想，以提高涂层的力学和耐磨性能。探讨制备工艺对粉末包覆效果、富钼层尺度及微观结构的影响，阐明网状结构粉末的形成机制，实现喷涂粉末的可控制备；研究富钼相网状结构特征及其尺度对MoSi2涂层的力学性能、结合强度和摩擦磨损性能的影响规律，弄清网状结构MoSi2涂层的微观结构、力学性能和摩擦学性能之间的关联性；揭示富钼相网状分布改性MoSi2涂层的韧化机理、结合机理和耐磨机理，阐明复合涂层的磨损失效行为及其机制。研究成果为高性能耐磨涂层材料的研制提供理论支持和实验依据，对丰富和发展摩擦学理论与设计具有重要的意义。

金属间化合物MoSi2有望成为一种新型耐磨涂层材料，可广泛应用于航空、航天、冶金、石化等领域中重要零部件表面耐磨防护，但MoSi2涂层脆性大和结合强度弱等缺陷制约着其应用，喷涂MoSi2涂层的韧性及其结合强度的提高是其耐磨应用所需要解决的重要问题。项目运用非均相沉淀+热还原以及喷雾干燥等方法制备了MoSi2，Mo-MoSi2和ZrO2-MoSi2等系列喷涂粉末；研究了MoSi2及其复合涂层的制备工艺、微观组织结构与力学性能之间的关系，揭示了MoSi2及其复合涂层的结合机理和强韧化机理；评价了复合涂层在不同温度和载荷下的摩擦磨损性能，阐明了MoSi2及其复合涂层的摩擦磨损机理。主要研究结果如下：（1）通过液相沉淀法-热还原工艺过程的优化，能够实现Mo-MoSi2包覆复合粉末的制备。（2）建立了大气等离子喷涂用MoSi2球形粉末的制备方法，优化了涂层中MoSi2为主相的MoSi2喷涂粉末的粒度范围为38-76μm；进一步通过粉末粒度优化和喷涂工艺控制，可以获得富钼相网状结构Mo-MoSi2复合涂层。（3）MoSi2涂层等离子喷涂制备最佳工艺为：电流500A；电压70V；喷涂距离100mm；送粉量26g/min；氩气流量45L/min。（4）等离子喷涂Mo涂层与基体结合强度为42.2MPa，硬度329.0 HV。与GCr15对摩时，Mo涂层在室温和300°C时摩擦因素分别为0.52和1.14，300°C时磨损率（11.2×10-5 mm3/N.m）是室温下的5倍；Mo涂层磨损机理主要为涂层剥落、氧化和粘着磨损。（5）Mo能够减少MoSi2涂层的孔隙，增加涂层的韧性和结合强度。MoSi2-Mo涂层的摩擦因数和磨损率均比Mo和MoSi2小。MoSi2-Mo涂层磨损机制主要为塑性变形、氧化和粘着磨损。（6）纳米ZrO2降低了MoSi2涂层的摩擦因数，减少了MoSi2涂层的脆性脱落，增加其抗粘着能力，提高了MoSi2涂层抗磨耐磨能力，ZrO2-MoSi2涂层磨损机制为氧化磨损和轻微粘着磨损。新型高性能MoSi2基耐磨涂层材料设计、制备方法和相关理论的研究，对于研发适应于恶劣环境下的耐磨防护涂层材料具有非常重要的意义。