Jin Yuanyuan, Xie Cheng, Sun Ke, Li Zehuan, Wang Xin, Ma Xin, Wang Hui, Shang Rongrong, Zhou Xuxian, Li Yidi, Li Yunping
State Key Lab for Powder Metallurgy, Central South University, Changsha 410083, China.
Aero Engine Corporation of China, South Industry Co., Ltd., Zhuzhou 412002, China.
Materials (Basel). 2025 Aug 25;18(17):3979. doi: 10.3390/ma18173979.
In this study, 10% nitric acid was employed to remove the aluminum coating on the cobalt-based superalloy K6509, with a focus on elucidating the corrosion mechanism and evaluating the effect of ultrasonic on the removal process. The results shows that ultrasonic treatment (40 kHz) significantly improves coating removal efficiency, increasing the maximum corrosion rate by 46.49% from 2.5413 × 10 g·s·mm to 4.7488 × 10 g·s·mm and reducing removal time from 10 min to 6 min. This enhancement is attributed to cavitation effect of ultrasonic bubbles and the shockwave-accelerated ion diffusion, which together facilitate more efficient coating degradation and results in a smoother surface. In terms of corrosion behavior, the difference in phase composition between the outer layer and the interdiffusion zone (IDZ) plays a decisive role. The outer layer is primarily composed of β-(Co,Ni)Al phase, which is thermodynamically less stable in acidic environments and thus readily dissolves in 10% HNO. In contrast, the IDZ mainly consists of CrC, which exhibit high chemical stability and a strong tendency to passivate. These characteristics render the IDZ highly resistant to nitric acid attack, thereby forming a protective barrier that limits acid penetration and helps maintain the integrity of the substrate.
在本研究中，采用10%的硝酸去除钴基高温合金K6509上的铝涂层，重点是阐明腐蚀机制并评估超声对去除过程的影响。结果表明，超声处理（40 kHz）显著提高了涂层去除效率，最大腐蚀速率从2.5413×10 g·s·mm提高了46.49%，达到4.7488×10 g·s·mm，去除时间从10分钟缩短至6分钟。这种增强归因于超声空化气泡的作用以及冲击波加速的离子扩散，它们共同促进了涂层更高效的降解，并使表面更光滑。在腐蚀行为方面，外层与互扩散区（IDZ）之间的相组成差异起决定性作用。外层主要由β-(Co,Ni)Al相组成，在酸性环境中热力学稳定性较差，因此容易溶解在10%的HNO中。相比之下，IDZ主要由CrC组成，其具有高化学稳定性和强烈的钝化倾向。这些特性使IDZ对硝酸侵蚀具有高度抗性，从而形成一个保护屏障，限制酸的渗透并有助于维持基体的完整性。
