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对扩散热处理后的热浸镀铝1Cr18Ni9Ti奥氏体不锈钢进行1000℃高温氧化试验,发现直接扩散处理试样在氧化120 h后表面出现明显开裂,而少无氧扩散处理试样经500 h氧化后表面完好。通过金相显微镜、扫描电镜和能谱仪的观察及分析表明,由于扩散前期在外扩散层形成的Fe-Al合金(脆性相Fe2Al5和条状FeAl2)为氧提供了扩散通道,导致直接扩散试样的合金层内产生了内氧化空洞,在高温氧化阶段,内氧化占据主导地位,使镀层表面开裂。少无氧扩散能够防止氧进入合金层内部,而且随着扩散的进行,合金层的相组成及形态变化也对氧向内扩散起阻碍作用。少无氧扩散试样的高温氧化由外向内进行,延缓了合金层的开裂和脱落。
The hot-dip aluminized 1Cr18Ni9Ti austenitic stainless steel after the diffusion heat treatment was subjected to 1000 ℃ high temperature oxidation test. It was found that the surface of the sample after direct oxidation was obviously cracked after oxidation for 120 h, while the samples with less oxygen diffusion after 500 h oxidation The surface is intact. The observation and analysis by metallographic microscope, SEM and EDS showed that the diffusion channels were provided for the oxygen due to the formation of Fe-Al alloys (brittle phase Fe2Al5 and stripped FeAl2) in the outer diffusion layer at the early stage of diffusion, resulting in direct diffusion of the sample Of the alloy layer generated within the oxidation hole, in the high temperature oxidation stage, the dominant internal oxidation, the coating surface cracking. The less anaerobic diffusion prevents oxygen from entering the alloy layer, and as the diffusion progresses, the phase composition and morphology of the alloy layer also hinder the inward diffusion of oxygen. Less oxygen-free diffusion of high-temperature oxidation of samples from the outside to inside, delaying the alloy layer cracking and falling off.