0.5Al alloys at 1023K and 1223K are shown in Fig.2a and Fig.2b.From above results,it can be known that the critical oxygen partial pressure of Fel7- Cr1.5Si0.5Al alloy are systematical lower than those of Fe25Cr alloy.Thus it can be concluded that the Fe17Cr1.5Si0.5Al alloy is better than Fe25Cr alloy in suppresion of sulfidation at these conditions -5.0 -6.0 -5.0 -7,0 ●Fe-25Cr-1.5Si-0.5A里 -6.0 Fe-25Cr-1.5si-0.5A alloy OFe-25Cr alloy o Fe-25Cr alloy -8.0h -22.0-21.0 -20.0-19.0-18.0 -17.0-16,0 -15.0-14.0-13.0 .1og(Foz/101kPa) log(P /101kPa) (a) (b) Fig.2 The kinetic boundary of Fe25Cr and Fe17Cr1,5Si0.5Al alloys,a.1023K;b.1223K 2.2 X-ray Diffracticn The phases of various reaction products formed on Fe-25Cr and Fe17Cr1,5 Si0.5Al alloys were different and varied with the gas composition as can be seen in Table 1 and Table 2 which list some representative analysis.The scales formed on Fe25Cr alloy consisted mainly of CrxSy,FeCr2S,Cr2Os when the gas composition was near to transition value.When the oxygen partial pressure is greatly higher than the critical one,the main phase is Cr2O3 with a small amount of FeCr2O,and CrxSy.The scales formed on Fel7Cr1.5Si0.5Al alloy consisted mainly of CrxSy, FeCraS,CraO,and FeaSiO when the gas composition was near to the trasition value.When oxygen partial pressure is greatly higher than the critical one,the main phases are Cr2O,and Fe2SiO.with a small amount of FeCr2S,and CrxSy. Table 1 X-ray diffraction of corrosion products of Fe25Cr alloy Treatment conditions temp. po21ps2 period K kPa h Phase 1023 1.47×10-18/3.28×10-6 1.5 FeCr2S,CrxSy,Cr2O3 1223 1.51×10-12/1.92×10-3 2.0 CrxSy,Cr2O3,FeCr2S 1223 1.48×10-14/6.22×10-8 2.0 Cr203,CrxSy 607、 五。 叭 · · 一 ， 。 一 。 产 万 广 厂 一 一 卜 尹 ’ ’ “ ，， ， 一 已， ︶工、衅锣。 、了 一驴 气 述 一 目 夕 万 声 才 尸 一 尸 一 一 碑 气 ’ 。 百 ， 。 。 ‘ 、 一 一 ， ， 红 一 节 一 二 ， ‘ ， 飞 ， 。 。 。 ， 声 ‘ ， ‘ 一 ， 习 · ‘ 一 丫 竺 ， ， 一 写口二‘ 尾二二 ‘ 二二二目 目翻二口 ‘ ‘ ‘ 书目二 二 口 ‘ ‘ ‘ 老二吕翻公二二二二二二 ‘ 二二二二二二刀之汽‘ 二 留曰咭二二二二 吧翻 ， 。 ‘ ’ 。 “ 。 一 ‘ 。 一 ” 。 一 ‘ 。 一 “ 。 。 。 ， ， ， ， 声 ， ，叹