铁铬镍基高温合金耐熔融NaCl腐蚀性研究(英文)

Corrosion Behavior of Cr, Fe and Ni Based Superalloy in Molten NaCl

熔融NaCl作为相变储热介质对容器材料具有强烈腐蚀性。通过对Cr基、Ni基和Fe基合金在850℃熔融NaCl中192 h的腐蚀实验,绘制了其腐蚀动力学曲线;利用SEM、EPMA、EDS、XRD等方法分析了腐蚀后试样横截面特征、元素分布特点及试样表面的腐蚀产物,讨论了腐蚀行为。结果表明:3种合金均满足线性腐蚀规律;Cr元素与熔融NaCl等物质反应,是导致这3种合金质量损失率增大的主要原因。Cr基合金耐蚀性最差,明显表现出晶界腐蚀特征,并且晶界为熔融NaCl渗入合金基体提供通道,促进了反应进程。Ni基合金和Fe基合金试样表面均形成了较厚的腐蚀层,为Cr2O3提供附着基体,降低了Cr元素扩散驱动力,提高了合金耐蚀性。另外,Fe基合金表面形成了尖晶石结构的腐蚀产物,进一步抑制了腐蚀过程,其耐蚀性最好。

Molten NaC1 is a strong corrosive substance for its container when NaC1 acts as solar high-temperature phase change thermal storage medium. The corrosion kinetics curves were measured and drawn by means of a 192 h corrosion experiment of Fe, Cr, Ni-base alloys in 850 ~C molten NaC1. The cross section characteristics, the elements distribution features and the corrosion products of the samples were analyzed after corrosion by SEM, EPMA, EDS and XRD, and the corrosion mechanism was studied. The results show that the corrosion kinetics curves of three kinds of the alloys obey the linear law, the acceleration of mass loss rate for the three kinds of a alloys can be attributed to the reactions among chromium and NaC1, etc. Chromium based alloy shows the worst corrosion resistance among the three alloys, with the characteristic of corroding along grain boundaries （which provide channels for the infiltration of molten NaC1 to alloy matrix）, hence the corrosion process is accelerated. A thicker corrosion layers are formed on the surfaces of the nickel based and the iron based alloys, which provide a foundation for the adherence of Cr203. The adherence of Cr203 can lower the driving force of the Cr diffusion, which improves the corrosion resistance of the alloy. In addition, a spinel structure layer of corrosion product is formed on the surface of the iron based alloy, which improves the iron based alloy corrosion resistance ulteriorly, and makes it perform the best corrosion resistance among the three alloys.