超音速电弧喷涂Monel合金涂层的电化学腐蚀特性

利用超音速电弧喷涂技术制备了Monel合金涂层,采用扫描电镜、能谱分析、X射线衍射等分析了涂层的显微结构、成分和相组成,并对涂层的结合强度和耐腐蚀性能进行了测试.研究表明,工艺参数对涂层的显微结构影响较小,局部结合界面区域出现孔隙;涂层主要由镍铜无限固溶相组成;涂层的结合强度和耐蚀性能随着电弧电压的升高而提高,平均结合强度最高达到23.25 MPa.涂层在5%HCl酸性溶液中,H+的浓度与腐蚀速率成正比,电位基本稳定在-400 m V并逐渐下降;在5%Na OH溶液中能很好地保护基体,涂层中的镍优先腐蚀而发生脱镍现象,4 h后腐蚀电位已趋于平衡,约为-300 m V.

Electrochemical corrosion behavior of Monel alloy coating produced by supersonic arc spraying

The Monel K-500 alloy coatings are sprayed by high velocity arc spraying with different spray parameters. The microstructure is investigated by SEM, chemical composition is measured by energy diffraction, and the phase composition is tested by XRD. There are little differences in microstructure among coatings. Particles deform fully in the coating, and the coating bonds well with the substrate except some pores in partial bonding area. The coatings are mainly composed of Ni-Cu infinite dissolved phase. The average bonding strength of the coatings increases with the increase of arc voltage, which reaches 23.25 MPa. Monel coating has good corrosion-resistance capability to mild salt fog which is better than pure aluminum coating. Energy dispersive X-ray spectroscopy and X-ray diffraction spectrum show that the corrosion products contain oxygen as the main element along with oxygen indicating that oxidation may have been taken place. The density of H+ is directed proportion to corrosion rate, and the hydrogen over-potential decreased to -400 mV in 5% HCl solution. In alkaline 5% NaOH solution, the Fe substrate was protected by the Monel alloy coatings, where, the Nickel phase in the coatings was corroded optimally when cathodically polarized at -300 mV after 4 hours.