空蚀-冲蚀-腐蚀耦合作用下WC基金属陶瓷涂层的损伤行为研究

Ocean power generation is an effective way in tackling energy shortage. However, many flow-handling components of hydraulic machinery in power generation systems were subjected to coupled damage in the process of cavitation erosion, erosive wear and corrosion, which would hinder the development of ocean energy. In this project, preparation of WC-based cermet coatings to cavitation erosion and erosive wear resistance in corrosion environment is achieved through studying the effect of high-velocity oxygen-fuel (HVOF) spraying parameters on microstructures and performance of the coatings and revealing the mechanism of their formation. Coupling law, damage behavior and the effect of microstructural change on the coupled effects resistance are revealed by coupling test of cavitation erosion and erosion-corrosion. Gradual change law of composition and microstructure of the coatings in the process of coupled damage are explored. Coupled damage mechanism of the coatings is clarified, and physical damage model is attempted to be established. The results of this proposed project are potential to provide theoretical foundation and technical support for the application of WC-based cermet coatings in coastal hydraulic machinery.

海洋能发电是缓解能源短缺的有效途径。然而，发电系统的水工金属过流构件在空蚀、冲蚀磨损与海水腐蚀过程中面临严重的耦合失效，制约了海洋能的开发利用。为此，本项目拟通过研究超音速火焰（HVOF）喷涂工艺参数对涂层组织性能的影响及揭示涂层的形成机理，实现腐蚀环境下抗空蚀耐冲蚀WC基金属陶瓷涂层的制备；对涂层进行空蚀-冲蚀-腐蚀耦合实验研究，阐明涂层微观组织演变对其抵抗耦合作用能力的影响机制，并在探讨不同结构涂层空蚀、冲蚀、腐蚀三种损伤行为的基础上深入分析三者耦合作用下的相互影响规律；探明耦合损伤过程中涂层成分和微结构的变化规律，揭示涂层的空蚀-冲蚀-腐蚀耦合损伤机理，建立相应的损伤物理模型；为WC基金属陶瓷涂层在沿海水工金属过流构件上的应用提供理论基础与技术支持。

海洋能发电是缓解能源短缺的有效途径。然而，发电系统的水工金属过流构件在空蚀、冲蚀磨损与海水腐蚀过程中面临严重的耦合失效，制约了海洋能的开发利用。本项目基于Taguchi设计理念，优化了WC基金属陶瓷涂层的喷涂工艺参数，探明了喷涂工艺参数对涂层组织性能的影响规律；阐明了涂层的微观组织结构与显微硬度、弹性模量的关系，揭示了涂层中非晶纳米晶相的形成机理；研究了涂层的组织结构和力学性能对其抵抗空蚀-冲蚀-腐蚀耦合作用能力的影响机制，探明了涂层在冲蚀腐蚀与空蚀过程中的耦合损伤行为、机理及耦合作用规律。重要结果包括：WC-CoCr涂层的综合性能随着喷涂距离的增大而减小，随着氧气流量和煤油流量的增加呈现出先增大后减小的趋势；WC-CoCr涂层主要由非晶相和WC、W2C的晶体相组成，涂层致密度、硬度和弹性模量高，与基体结合良好；非晶相形成的原因是熔融液态粒子具有高的瞬时凝固速率和喷涂粉末拥有多组分的合金元素体系，纳米晶主要是由非晶晶化均匀形核产生；金属陶瓷涂层的空蚀率随流速增大而增大，抗空蚀性能从高到低依次为WC-CoCr涂层＞WC-Cr3C2-Ni涂层＞Cr3C2-NiCr涂层＞WC-Ni涂层；含沙量一定时，金属陶瓷涂层的冲蚀率和磨蚀率随流速增大而增大；流速一定时，涂层的冲蚀率和磨蚀率随含沙量增大亦增大；涂层破坏从表面的孔隙、裂纹等缺陷处萌生，沿相界面扩展；增大硬质相体积分数，提高涂层硬度和相界面结合强度，有助于提高涂层抗磨蚀性能。本项研究丰富了多相流条件下抗空蚀材料的理论基础，在沿海水工金属过流构件的防护方面有良好的应用前景。