等离子体喷涂钨涂层表面自纳米化关键技术及其强化机理研究

Plasma spraying technology is a viable fabrication method of the tungsten (W) plasma facing material (PFM) because of its simplicity, possibility to cover complex and extended surfaces, in situ repair of damaged parts and relatively low cost. The current related research almost focus on W coating fabrication on Copper (Cu) substrate and the heat flux performance testing of W/Cu plasma facing component ( PFC). But few studies have been reported on the surface modification of W coating in order to enhance heat flux performance and prolong service time, especially on key technology research of W PFM surface self nano-crystallization. The project will carry out the surface nano-crystallization of W coating, which is based on the research results of the interface characteristic of W/Cu PFC and the damage evolution of W coating. The surface self nano-crystallization of the plasma sprayed tungsten coating will be fabricated by means of the ultrasonic shot peening technology, and heat load tests of W/Cu PFC with the surface nano-crystallization are carried out by the electron beam facility. The heat flux performances of the surface nano-crystallization W coating will be evaluated by their heat transfer capability in time, the thermal fatigue lifetime, the heat load limit. Meanwhile, the finite element method also was applied to comparison with the results of electron beam heat loading tests. The effect and improvement mechanism of the surface self nano-crystallization on the heat flux performances and the physical properties will be discussed.In addition, it will by analyzed that the damage evolution and the failure behaviors with the increase of the load power density. The project will provide not only the scientific basis and data accumulation for W PFM properties strengthening, but also can accelerate the development of W/Cu PFC.

等离子体喷涂技术成熟、成本较低、可以实现复杂形状样品大面积喷涂、具有损坏位置定点修复的优点而被认为是制备钨面对等离子体材料比较适合的一种方法。国内外在钨涂层面对等离子体材料方面的相关研究主要集中在钨材料制备工艺以及热负荷性能实验研究，针对其提高热负荷性能、延长服役寿命的钨涂层表面自纳米化表面改性关键技术的研究未见报道。本项目是在对等离子体喷涂钨/铜第一壁界面特征、损伤行为系统研究的基础上利用超声喷丸技术开展钨涂层面对等离子体材料表面自纳米化研究，通过电子束热负荷实验平台并结合ANSYS有限元分析综合评价纳米化钨涂层面对等离子体材料实时传热能力、热疲劳寿命、热负荷承受极限等性能，分析纳米化钨涂层损伤演化过程及失效行为，阐明表面纳米化对钨涂层面对等离子体材料服役性能影响及增强机理。本项目研究不仅可为钨面对等离子体材料强化改性提供数据参考，也有助于促进钨/铜面对等离子体部件的发展。

核聚变实验装置托卡马克在运行过程中会不断有热负荷能量流以及粒子流沉积到内壁上，面对等离子体材料的性能优劣成为关系到核聚变装置能否正常运行的关键问题之一。高Z材料钨由于具有较高的熔点、较低的溅射率、较高的热导率等优点而被认为是最有前景的面对等离子体材料。但是热负荷疲劳作用下，钨PFM表面裂纹、裂纹扩展、气孔聚合等影响材料热移除性能和使用寿命。喷丸技术适用范围广、实用性强、操作方便、成本低等优点而被广泛应用到机械材料的前面强化中，能够显著改善材料表面性能，减少制造时的残余应力，增强材料力学性能。本项目利用喷丸技术对钨表面进行强化，开展相关研究。通过喷丸前后微观形貌、晶粒细化、表面粗糙度、表面硬化和表面残余压应力等性能表征量变化与陶瓷丸直径、喷丸压力、喷丸距离等喷丸参数之间的关系对喷丸参数影响因素进行系统分析，开展钨材料表面强化性能的实验研究。陶瓷丸料大小和喷丸压力决定喷丸强化效果，喷丸距离影响较小。在0.3MPa-0.6MPa压力范围内，陶瓷丸料大小是影响强化表面硬度的主要因素，对0.3mm-0.5mm陶瓷丸，喷丸压力是影响表面粗糙度的主要因素。在100%覆盖率情况下，0.3MPa喷丸压力、0.4mm陶瓷丸、100mm垂直喷丸距离是比较合适的喷丸参数，其材料表面性能提高显著。表面硬度提高高达53.3%，残余压应力提高8.3倍，表面细化晶粒现象明显，而且对表面粗糙度影响不大，最高1.5μm左右。因此，在聚变物理实验绝大多数还处在放电脉冲短、频次高的阶段，钨表面对W-PFM疲劳性能的改善具有重要意义。