两相Fe-Cu合金的硫化腐蚀特性

THE NATURE OF SULFIDE SCALES ON TWO PHASE Fe Cu ALLOYS

研究了Ｆｅ－２５Ｃｕ、Ｆｅ－５０Ｃｕ和Ｆｅ－７５Ｃｕ在硫压高于二组元硫化物分解压条件下的高温硫化，并着重于硫化反应产物结构特征．各合金的腐蚀速率均低于纯铁和铜，其中Ｆｅ－２５Ｃｕ最慢而Ｆｅ－５０Ｃｕ最快．合金形成复杂的硫化膜结构：其外层为两种二元复合硫化物（Ｃｕ５ＦｅＳ４和ＣｕＦｅＳ２）的细微混合层；其内层含未被硫化的金属态α（Ｆｅ）相粒子和源于β（Ｃｕ）的内硫化物Ｃｕ５ＦｅＳ４．由于金属向外迁移的结果，该区域常有大量孔洞形成．硫向合金内的渗透速率随铜含量和温度的升高而增加．此外，在外／内硫化膜界面上形成一些纯金属铜颗粒，它们或呈粒状并被硫化物所包裹、或呈胡须状突出于硫化膜之外．就双相合金腐蚀区别于固溶体合金的特性，对所得实验结果进行了讨论．

The sulfidation of two phase Fe Cu alloys containing 25, 50 and 75 wt% copper has been studied at 500 and 600℃ under sulfur pressures higher than those for the dissociation of iron and copper sulfides. A special attention has been devoted to the examination of the microstructure of the scales. Fe 25Cu sulfidized at the slowest rates, whereas Fe 50Cu corroded more rapidly than the other two alloys. The scales contained an outer layer of a mixture of two Cu Fe double sulfides (Cu 5FeS 4 and CuFeS 2), plus an inner region of sulfidation concerning mainly the Cu rich β phase and also of some Fe rich α phase forming Cu 5FeS 4 plus large voids, possibly due to outward diffusion of metal cations. The depth of this zone increased with temperature and iron content. Moreover, pure copper metal particles formed at the scale/subscale, as whiskers protruding out of the external scale surface. The results obtained are examined with special reference to the two phase nature of these alloys.