强流脉冲离子束辐照核级硬质合金涂层复相协同冲击应变机制研究

以Ni替代产生放射性的Co做粘结相的无钴WC基硬质合金热喷涂涂层，在核主泵泵轴、轴承及密封等关键部件耐磨抗蚀应用，但无钴化涂层强度硬度有所降低，亟待发展有效的涂层强化技术以满足核电装备高可靠、长寿命安全运行要求。目前基于重熔改性的激光和电子束等工艺因深层熔化易形成贯穿热裂纹及大量脆性相，涂层强化效果有限。本项目拟采用自主研发的大面积强流脉冲离子束表面工程技术，辐照无钴WC基硬质合金热喷涂涂层，研究辐照非平衡热-力耦合无约束冲击作用（离子射程区快速加热、熔化与烧蚀，及由此产生向内传播的冲击应力波），通过对辐照涂层的材料学分析、磨损腐蚀及疲劳行为研究，掌握低应力重熔浅表层和深达数百微米冲击应变层的耦合形成规律，探明辐照涂层的WC硬质相/金属粘结相复相结构的协同冲击应变机制及其对性能改善作用，发展出核级硬质合金涂层耐磨抗蚀抗疲劳复合强化新技术，为有效提升涂层性能、拓展其在核电装备中应用创造条件。

Substituting Ni for radioactive Co as binder phase in WC based cemented carbide thermal sprayed coatings is promising for wear- and corrosion- resistant applications in key components of nuclear coolant pump in nuclear power plants, such as shafts, bearings and mechanical seals. However, Ni cemented carbide coatings possess lower strength and hardness in comparison with the Co counterparts. Effective strengthening of WC-Ni cemented carbide coatings are indispensable for high reliabile and safe long term run of the equipments in nuclear power plants. Laser and elecltron beams technonlogies of remelting principle, currently available for strengthening of thermal spary coatings, are still not sufficient for the cemented carbide coatings applications due to formation of penetrating cracks or brittle phases, as a result of thermal stress and chemical reaction induced by notable thermal effect across the entire coating up to a few hundreds micrometers. In this project, a high-intensity pulsed ion beam approach is proposed to improve the overall properties of nuclear grade WC-Ni coatings, based on unconfined shock strengthening principle instead of deep remelting of the coatings. The shock processing is to be investigated concerning the non-equilbrium coupled thermal-dynamical effects (involving ultra-fast heating, remelting and ablation in the ion-implanted top layer within a few micrometers) and thus produced strong shock stress waves propogating inwards. The coupled formation of a thin top remelted layer and a deep shock deformation layer down to a few hundreds micrometers will be clarified through characterizations of shock deformed microstructures and resultant wear, corrosion and fatigue properties. Synergetic shock deformation behavior of the biphase structure in the coatings, i.e. WC hard phase and Ni binder, will be particularly studied in addition to its effect for improving the coatings' wear, corrosion, and fatigue resistance, to develop a new and reliable apprach to improving the overall properties of WC based cemented carbide coatings, extending their applications in the equipments in nuclear power plants.