李处森
,
杨院生
中国腐蚀与防护学报
叙述了碳气氛温度、金属材料种类及表面状态、构成碳源的气体种类、比例及流速等因素对金属材料结焦行为的影响，介绍了催化结焦的引发机理及其应用。然后以FeCrNi合金为例，分别介绍了内部渗碳和金属粉化这两种渗碳行为，并叙述了温度、碳气氛、合金材料晶体结构及成分构成的影响。最后分析了结焦和渗碳的关系，并介绍了添加结焦抑制剂、调整金属材料结构及成分构成、表面涂层化3种防护对策。
关键词:
金属材料
,
coking
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carburizing
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metal dusting
J.Q.ZHANGD.J.YOUNG
中国腐蚀与防护学报
Metaldusting attacks iron, low and high alloy steels and nickel-or cobalt-base alloys by disintegrating bulk metals and alloys into metal particles in a coke deposit. It occurs in strongly carburising gas atmospheres (carbon activity aC>1) at elevated temperatures (400 ℃~1000 ℃). This phenomenon has been studied for decades, but the detailed mechanism is still not well understood. Current methods of protection against metal dusting are either directed to the process conditions-temperature and gas composition-or to the development of a dense adherent oxide layer on the surface of the alloy by selective oxidation. However, metal dusting still occurs by carbon dissolving in the base metal via defects in the oxide scale. The research work at UNSW is aimed at determining the detailed mechanism of metal dusting of both ferritic and austenitic alloys, in particular the microprocesses of graphite deposition, nanoparticle formation and underlying metal destruction. This work was carried out using surface observation, cross-section analysis by focused ion beam and electron microscopic examination of coke deposits at different stages of the reaction. It was found that surface orientation affected carbon deposition and metal dusting at the initial stage of the reaction. Metal dusting occurred only when graphite grew into the metal interior where the volume expansion is responsible for metal disintegration and dusting. It was also found that the metal dusting process could be significantly changed by alterations in alloy chemistry. Germanium was found to affect the iron dusting process by destabilising Fe3C but increasing the rate of carbon deposition and dusting, which questions the role of cementite in ferritic alloy dusting. Whilst adding copper to iron did not change the carburisation kinetics, cementite formation and coke morphology, copper alloying reduced nickel and nickel-base alloy dusting rates significantly. Application of these fundamental results to the dusting behaviour of engineering alloys is discussed.
关键词:
metal dusting
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null
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null
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null
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null
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雷娜
,
周昌玉
,
胡桂明
,
陈成
钢铁研究学报
金属材料在CO-H_2-H_2O合成气氛使用过程中会发生金属尘化腐蚀.运用化学热力学理论与计算方法对在CO-H_2-H_2O气氛下发生金属尘化腐蚀时的标准反应吉布斯函数进行计算,得到了气氛碳活度与温度的关系式.通过气氛碳活度与材料碳活度的比较,获得两种金属尘化类型.CO-H_2-H_2O气氛碳的化学势受温度、气氛组成、总压的影响,减少H_2O的含量,升高总压,会使发生金属尘化的温度范围扩大.
关键词:
金属尘化
,
热力学
,
碳活度
,
化学势
,
碳
刘刚
,
蒋晓东
,
董雷云
腐蚀与防护
针对一段发生腐蚀穿孔失效的乙烯裂解炉炉管,采用宏观腐蚀形貌观察、材料化学成分分析、显微组织检查、腐蚀产物能谱分析等理化检验,结合炉管的工作条件进行失效分析,并提出建议改进措施.结果表明,向火面炉管腐蚀穿孔失效是由于高温下Cr2O3保护膜破坏而发生的金属粉化失效.对此次失效机理的探讨表明金属粉化在高于800℃温度下仍有可能发生,表面Cr2O3保护膜的破坏是关键因素.
关键词:
乙烯裂解炉管
,
腐蚀穿孔
,
金属粉化
,
失效分析
陈成
,
周昌玉
,
胡桂明
,
雷娜
材料保护
金属渗碳腐蚀(即尘化)是高温碳氢环境下常发生的灾难性腐蚀.Cr5Mo 钢的工程应用量大面广,过去对其渗碳腐蚀研究不够.为此,研究了炉管材料Cr5Mo钢在600 ℃,50%CO-H_2-3%H_2O气氛下的尘化腐蚀行为,采用X射线衍射分析了腐蚀试样的物相组成,采用扫描电镜对试样进行了微观形貌分析.结果表明:Cr5Mo 钢在试验条件下呈现均匀腐蚀,材料自表面向内依次析出Fe_5C_2和Fe_3C脆性腐蚀产物,经560 h尘化腐蚀后的试样平均腐蚀深度约为200 μm,而基体材料性质无明显改变.因此Cr5Mo 钢在尘化过程中出现的腐蚀减薄是由脆性碳化物层的析出引起的.
关键词:
金属渗碳腐蚀
,
Cr5Mo钢
,
减薄
,
表面状态
