镍铝青铜空蚀过程中机械作用/化学腐蚀协同效应及其钝化膜动态回复机制研究

Nickel-aluminum bronze faced the outstanding problem of cavitation erosion failure when servicing in the marine condition. The theory of cavitation erosion has not yet been clarified. And the characteristics of cavitation erosion under different working conditions should be further explored. It was studied that the synergistic effect of mechanical action/chemical corrosion as well as the dynamic recovery mechanism of the passive film during the cavitation erosion process of Ni-Al bronze. It was revealed that the mutual mechanism between the cavitation attack and the corrosion during the intermittent pulse cavitation. The forming characteristics of the surface passivation film and its influence on the process of cavitation erosion were also clarified. The effect on the cavitation behavior of cavitation mode and cavitation media was investigated to construct the constitutive equation of servicing condition，material component and cavitation characteristic. The systematic evaluation system was also established based on the material properties parameters. The cathodic polarization potential was applied to suppress the corrosion reaction. The acidic cavitation media was also introduced to eliminate surface passivation film. And then the mechanical mechanism was directly characterized as well as the mechanism of passivation film. It was clarified that the interaction mechanism between mechanical damage and chemical corrosion during the cavitation process of nickel-aluminum bronze to develop the existing cavitation erosion theory. It is believed to provide a theoretical basis and data support for the cavitation application of nickel-aluminum bronze in the marine equipment, which has important academic value and practical significance.

镍铝青铜作为海工装备动力部件在服役过程中面临空蚀破坏的突出问题，相关的空蚀机制理论尚未厘清，不同工况条件下的空蚀行为特性也有待进一步深入探索。本项目通过研究镍铝青铜空蚀过程中机械作用/化学腐蚀协同效应及其钝化膜动态回复机制，揭示间歇脉冲空蚀过程中空泡冲击与腐蚀作用之间的互做机制，阐明表面钝化膜的成膜特性及其对空蚀进程的影响规律。通过研究空蚀模式、空蚀介质对空蚀行为的影响进程，构建工况因素-材料组分-空蚀特性的本构关系方程，提出基于材料物性参数的系统评价体系；施加阴极极化电位抑制腐蚀反应，引入酸性空蚀介质消除表面钝化膜的影响，进而直接表征机械作用机制，直观反映钝化膜的影响机理；通过研究空蚀过程中镍铝青铜的机械损伤和化学腐蚀行为，阐明两者之间的交互作用机理，进而完善发展现有的空蚀理论，可以为镍铝青铜在海工装备中的耐空蚀应用提供理论依据和数据支撑，具有重要的学术价值和现实意义。

镍铝青铜合金因其所具有良好的机械性能和耐蚀性能而广泛应用于舰船螺旋桨等海工装备中，然而空泡腐蚀破坏经常导致镍铝青铜结构件提前腐蚀失效，是镍铝青铜在海水环境服役下突出的工程问题。因此，本课题研究了铸态镍铝青铜的微观组织和成分对其静态浸泡腐蚀和空泡腐蚀行为的影响，分析了空泡腐蚀过程中镍铝青铜表面腐蚀产物膜的演变规律，利用定量化方法说明空泡腐蚀过程中电化学腐蚀和机械冲击作用的协同效应，采用表面改性工艺和热处理方法提高铸态镍铝青铜的静态耐蚀性能和抗空蚀性能，主要研究结论如下：.1. 由于铸态镍铝青铜的微观组织不均匀性和相间电势差异大，导致选相腐蚀是其静态浸泡腐蚀过程的主要失效机制。对比不同热处理态的镍铝青铜的空蚀失重和力学性能，结果表明合金硬度低不耐机械冲击是铸态镍铝青铜空蚀失效的主要原因。.2. 微区电化学分析技术揭示了镍铝青铜表面微区腐蚀电流密度先变小后增大再减小的变化行为，裸露金属表面与腐蚀产物膜之间的电偶腐蚀和腐蚀钝化膜对露出金属表面的腐蚀保护是两个相互伴随过程，与镍铝青铜表面钝化膜的动态回复密切相关。.3.电化学腐蚀与机械冲击的协同机制如下：机械冲击通过增加溶液中的溶解氧加速阴极去极化过程促进腐蚀，同时破坏表面腐蚀产物膜的完整性促进下层金属溶解，电化学腐蚀使镍铝青铜表面不同微区之间的腐蚀产物膜机械性质存在差异，使其在机械冲击下更容易被被剥离，并氧化机械冲击破坏钝化膜露出新鲜的金属表面。.4.采用热处理、表面激光淬火、铬离子注入、热扩散和喷丸强化处理均可以均匀化铸态镍铝青铜表层微观组织，消除选相腐蚀，提高表面硬度，降低了空蚀程度。.本课题的研究成果揭示了铸态镍铝青铜静态浸泡腐蚀和空泡腐蚀的失效机制，为提高镍铝青铜的耐蚀性能提供理论依据，从工程应用角度出发采用表面改性工艺调控镍铝青铜微观组织和成分，提高镍铝青铜的静态耐蚀和抗空蚀性能，为新型船用镍铝青铜螺旋桨的研发提供了工程技术的参考指南。