In-situ Observation of Initial Reaction Stages of Hot-Corrosion

在燃油锅炉和燃气涡轮机系统中，高温热腐蚀由于其侵蚀性而日益受到关注。热腐蚀机理的研究主要采用电化学方法和熔盐化学方法，但对热腐蚀初期的研究较少，本研究采用扫描电镜观察了不同腐蚀环境下的熔化过程，得到的结果如下：(1)在扫描电镜上安装了差动抽气系统，使样品室保持在不同的腐蚀环境中。(2)安装了热台，加热到500摄氏度。(3)几种样品，低熔点合金（90 ℃），熔点200 ℃的ZnCl_2-KCl混合盐，和熔点为231摄氏度的纯锡金属，在低气压条件下观察到了熔体的熔化和凝固过程。然而，由于状态的快速变化，没有观察到熔化过程的细节。为了克服这个困难。应该需要视频监控系统。(4)研究了Fe-Cr合金在低硫压下的硫化过程，以阐明其晶界侵蚀机理。(5)总结并评述了与硫化有关的气体腐蚀。

In oil fired boiler and gas turbine systems high-temperature hot corrosion is increasing concerns, because of its aggressiveness. Mechanisms of the hot corrosion have been studied by using electrochemistry and fused salt chemistry, whereas there is little information on the initial stage of the hot corrosion.In this research project the scanning electron microscope was developed to observe the melting process in various corrosion environments.The results obtained are summarized as follows.(1) Differential evacuation system was installed to SEM in order to keep sample chamber in various corrosion environments. (2) Hot stage was installed, heating up to 500ﾟC. (3) Several samples, alloy with low melting temperature of 90ﾟC, mixed salt of ZnCl_2-KCl with 200ﾟC m.p., and pure tin metal with 231ﾟC m.p., were observed in the low air pressure and the melting and solidifing processes were observed clearly. However, details of the melting process was not observed because of rapid change in states. In order to overcome this difficulty. the video-monitoring system should be needed. (4) Sulfidation process of Fe-Cr alloys was investigated in low sulfur pressures in order to elucidate the mechanism of grain boundary attack. (5) Gaseous corrosion associated with sulfidation was summarized and critically reviewed.