采用粉末包埋法，分别以氯化铵、氯化钠、氯化镍为活化剂在镍基高温合金上于950℃进行了渗铬处理。扫描电镜和能谱分析结果表明，以氯化铵或氯化钠为活化剂得到的渗铬层以向外生长模式为主，但前者在与基体界面处夹杂氮/氧化物颗粒较多，同时含有高达约11．4％(质量分数)的Fe杂质，而后者在与基体界面处夹杂较少，渗铬层Fe含量仅为约1．4％(质量分数)，远低于前者。以氯化镍为活化剂得到的渗铬层则以向内扩散为主，与基体无明显界面，但 Ni 及杂质Fe(19．7％(质量分数))含量最高。氯化钠表现出净化渗铬层成分的作用，而氯化镍具有增强与基体互扩散的作用，因此，活化剂种类对渗铬层成分及结构具有重要影响。
Chromizing of superalloys at 950 ℃ by pack cementation with three different activators of ammonia chloride,sodium chloride and nickel dichloride was investigated.For the ammonia chloride activated system, outward growth of the chromized coating was observed.The coating contained a relative high amount of Fe im-purities of 1 1 .4wt%.Besides,a large amount of nitride/oxide impurities were embedded at the coating/sub-strate interface.For the sodium chloride activated system,similar outward growth manner of the coating was observed.But the Fe content decreased to about 1.4wt%.Meanwhile,less oxide impurities were observed at the coating/substrate interface.For the nickel dichloride activated system,the chromized coating grew inwardly.No apparent coating/substrate interface can be identified.And the coating contained much more Ni and Fe.These results indicate that sodium chloride is able to purify the chromized coating,while the nickel dichloride can en-hance interdiffusion between the coating and substrate.Hence,activators play an essential role in optimizing the microstructure and composition of chromized coatings in pack cementation method.
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