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

在燃油锅炉和燃气轮机系统中，高温热腐蚀因其侵袭性而日益受到关注。利用电化学法和熔盐化学法研究了热腐蚀的机理，但有关热腐蚀初期的信息很少，本研究项目开发了扫描电子显微镜来观察不同腐蚀环境下的熔化过程，主要研究结果如下：(1)在扫描电子显微镜上安装了差动抽气系统，以保证样品在不同腐蚀环境下工作。(2)设置热台，加热至500ﾟC。(3)在低气压下，观察到熔化温度为90ﾟC的合金、熔化温度为200ﾟC的氯化锌-氯化钾混合盐以及熔化温度为2 31ﾟC的纯锡金属的熔化和凝固过程。然而，由于状态的快速变化，没有观察到熔化过程的细节。为了克服这一困难。应该需要视频监控系统。(4)研究了Fe-Cr合金在低硫压力下的硫化过程，以阐明晶界侵蚀的机理。(5)对与硫化有关的气体腐蚀进行了总结和评述。

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.