WCp/钢基表层复合材料的组织控制及热疲劳特性研究

This project focused on the key issue that the thermal fatigue performance of WC particle reinforced steel substrate surface composite was not satisfactory under complex service of high temperature wear and sharp heat-cool cycle in industries, such as metallurgy, cement, electricity and so on. As investigated object, WCp reinforced steel substrate surface composite would be formed by SPS and interface remelting in vacuum, so that it is easier to investigate the relationship between the microstructure and the thermal fatigue performance.The dissolution-precipitation mechanism of the WCp in the matrix, the formation mechanism of the other phases, the formation mechanism of interface between the matrix and the particles and the formation mechanism of interface between the composite and the substrate are investigated.The influence of morphology and antioxidation of the phases on thermal crack initiation and propagation would be infered. In order to obtain the microstructure control mechanism and the connection between the morphology of microstructure and thermal fatigue. The results of this project could greatly extend the application area of WCp reinforced metal matrix surface composite and other materials containing similar microstructure, and offer new technological approaches and theoretical guidance to the technologies which can improve the thermal fatigue resistance in high-temperature wear and sharp quenching complex service.

项目以冶金、水泥、发电等行业广泛存在的高温磨损、激冷激热复合工况为应用背景，以碳化钨颗粒增强钢基表层复合材料为研究体系，采用等离子快速烧结 (SPS) + 真空界面重熔研究方法模拟材料的制备，选取极限工艺参数（如较大限度地降低或提高WCp体积分数），以便于由易到难地开展表层复合材料的热疲劳特性及其与组织的关联性研究。结合现代分析测试手段，探索碳化钨颗粒在基体中的"溶解-析出"机制、其它物相的生成机制及增强体与基体间和复合层与基材间的界面形成机制，研究各种物相的形态和分布规律及其抗高温氧化特性对热疲劳裂纹萌生、扩展的影响，以获得WCp/钢基表层复合材料的组织控制机制及组织与热疲劳特性间的关联机制。项目的实施将大大拓展陶瓷颗粒增强钢基表层复合材料及其他具有类似组织结构的材料的应用领域，为其在高温磨损、激冷激热等复合工况下热疲劳寿命的提高提供新的技术途径和可靠的理论指导。

近年来，WCp/钢基表层复合材料得到了较好的发展，有望在激冷激热工况下的冶金、机械等领域获得应用。但鉴于该类复合材料组织结构上的复杂性，欲解决以上应用问题，复合材料的热疲劳特性研究将成为重中之重。采用等离子快速烧结(SPS)+真空界面重熔法模拟制备了碳化钨颗粒增强复合材料。实现了复合材料基体组织的可控性，有效的排除了制备工艺缺陷对研究结果的影响。采用极限工艺法，制备了制备了不同极限工艺参数以及不同基体的复合材料，为从简到难研究复合材料的热疲劳性能提供了有利条件。在重熔处理过程中，随着重熔温度的升高，界面反应区的宽度呈增加趋势；界面反应产物为Fe3W3C，其形成过程为：1314 ℃下碳化钨颗粒内部发生反应：2WC→W2C+C，持续升温至1341 ℃，颗粒中的W2C与基体发生反应3Fe+W2C→Fe3W3C+1/2C。利用热震实验，对比不同基体组织和极限工艺法制备的复合材料的热疲劳性能。发现基体和增强颗粒之间的热膨胀系数差异及增强颗粒的自身脆性，导致裂纹在复合层中的萌生、扩展不可避免；珠光体为基体的复合材料热疲劳性能优于铁素体为基体的复合材料的热疲劳性能；裂纹更易在宏观界面的颗粒处扩展，且裂纹的萌生位置为颗粒与基体间的界面反应区处。