双连续梯度复合高铁制动材料的制备及其服役行为研究

Brake disk is a key parts to ensure the safety of railway transportation. Along with the rapid development of rail transit toward high speed and heavy load, the heat quantity caused by braking increase gradually, and lead to an obviours rise of the working temperature for the brake disk, which is close to the upper limit of permitted temperature for the braking materail. Therefore, developing a new type of braking materail with higher performances becomes a pressing problem. To satisfy the property requirments of braking material for high speed train, a three-dimensional continuous ceramic skeleton, with gradient pore distribution from one side to another, will be used to reinforce the recent braking steel, and a new type of double continuous gradient ceramic / alloy steel composites for high speed train braking material will be developed in this project. Ceramics feature resistance to high temperature, wear, corrosion and hot impact. Advanced frictional, wear and thermal fatigue properties are expected for the three-dimensional continuous ceramic skeleton reinforced alloy steel matrix composite, because its double continuous structure is beneficial to a tight connection between the matrix and the reinforcements, and the gradient distribution of the ceramic skeleton makes the reinforced composite layer join easily to the forged steel braking disk. In addition, on the basis of preparation technology optimization, the microstructure, properties and controlling technique of the interface between the ceramics and the alloy steel will be investigated in detail. The high temperature frictional, wear and thermal fatigue properties, mechanisms and influence factors will be revealed. This project will establish an application basis of the composite as a new type of braking material used in high speed train.

列车制动盘是保障铁路运输安全性的关键部件。随着铁路运输向高速、重载的方向发展，制动系统所承受的负荷越来越大，摩擦产生的热量使制动盘工作温度不断升高，已接近现有制动材料的工作上限，发展性能更优的新型制动材料已成为亟待解决的问题。针对高铁制动材料的性能需求，本项目拟采用一种陶瓷含量呈梯度变化的三维连续骨架增强相对现有制动用钢基体进行增强，研制一种新型双连续梯度陶瓷/合金钢复合制动材料，充分发挥陶瓷材料耐高温、耐磨损的优势，提高制动材料的高温摩擦磨损性能和热疲劳性能，同时通过基体与增强相的双连续来优化复合效果，强化两者的结合；通过增强相含量的梯度变化使复合材料一侧耐磨，另一侧易于与锻钢制动盘基体连接。此外，本项目在优化复合材料制备技术基础上，深入研究基体与增强相之间界面结构、特性及其调控方法，揭示复合材料高温摩擦磨损特性与热疲劳性能、机理及其影响因素，为这一新型材料在高铁制动领域的应用奠定基础。

本项目选用与铁基体润湿性良好的TiC为增强相，采用粉末冶金法制备了均质及梯度TiC/Fe复合材料，采用模板浸渍-熔融浸渗法制备了双连续TiC/Fe以及双连续梯度TiC/Fe复合材料，研究了材料组分、复合形式、工艺参数等对TiC/Fe复合材料结构及性能的影响，取得以下主要成果：.(1) 成功制备了均质、梯度结构、双连续结构以及双连续梯度结构TiC/Fe复合材料。.(2) 无压烧结制备的均质TiC/Fe复合材料中，15vol%TiC/Fe的致密度最高，达97.8%；20vol%TiC/Fe的硬度最高，达270HV。基体中添加羰基铁粉有助于降低烧结温度并促进致密化，添加少量硬脂酸锌可提高TiC/Fe复合材料的性能。.(3) 采用无压烧结工艺成功制备出TiC体积含量分别为5、10、15、20的TiC/Fe梯度复合材料，各梯度层间界面结合良好。.(4) 以聚氨酯海绵为模板制备了TiC多孔陶瓷增强体，在TiC原料中加入Ti粉可反应生成非化学计量比的TiCX颗粒，有利于提高增强体与铁基体的润湿性，加入少量Mo和Fe粉则可明显改善增强体的力学性能。.(5) 通过无压浸渗工艺制备了双连续TiC/Fe复合材料，TiC多孔增强体的成分对双连续TiC/Fe复合材料的性能影响显著，在增强体中添加少量Fe粉制备的双连续TiC/Fe复合材料的致密度最高，达99.8%，而添加少量Mo制备的双连续TiC/Fe复合材料的拉伸强度最大，为343 MPa，比相同增强相含量的无压烧结颗粒增强型复合材料提高了66.5%。.(6) 采用不同孔径的有机模板粘接法制备出梯度TiC多孔增强体，通过重复浸渍和烧结可有效提高增强体的性能，其抗压强度最高可达4.1MPa，在此基础上采用无压浸渗工艺制备出双连续梯度TiC/Fe复合材料。.(7) 摩擦磨损试验中，TiC/Fe复合材料的摩擦系数和磨损量随基体成分、TiC含量以及试验条件而改变，其中均质TiC/Fe复合材料的摩擦系数随TiC体积分数的增加而提高，双连续TiC/Fe复合材料的摩擦系数随增强相孔径尺寸的增加而增大，随着法向压强的变化不显著。双连续TiC/Fe复合材料耐磨性能显著优于颗粒增强型复合材料，0.5MPa压强下，增强相含量为4vol%的双连续TiC/Fe 复合材料的磨损率比相同含量的热压烧结颗粒型复合材料低43.9%，而比无压烧结颗粒型复合材料低1.95倍。