310不銹鋼與高鉻鑄鋼的高溫硫化行為

The Sulfidation Behavior of AISI 310 Stainless Steel and High-Chromium Cast Steel

本研究探討在10-3 ~ 1 atm的硫分壓區間，310不銹鋼與高鉻鑄鋼（Fe-27Cr）於7000900℃間的高溫硫化腐蝕行為。研究結果顯示，所有鋼材的腐蝕動力學均遵守拋物線型定律，且硫化腐蝕速率常數隨著溫度上升及硫分壓之增加而加快，但腐蝕速率常數與硫壓之指數關係（Kp ~ Ps21/n）則大不相同，對310不銹鋼而言，n值約在5.8 ~ 6.7之間，但高鉻鑄鋼之n值則在2.2~2.8之間。硫化後，所有鋼材皆生成複雜的雙層硫化物，其中，310不銹鋼的外層主要為(Fe,Ni)9S8，FeS/Fe1-xS以及少量Cr2S3／Cr3S4，內層則以Cr2S3, Cr3S4, NiCr2S4, FeS為主；高鉻鑄鋼的外層以硫化鐵（FeS/Fe1-xS）為主，另有少量的硫化鉻（Cr2S3/Cr3S4），內層則是硫化鐵及硫化鉻的混合相。白金指標位於內外硫化層之間，顯示陽離子向外擴散主導外層硫化物的生成；而內層硫化物的生成則由硫離子向內擴散所致。

High temperature sulfidation behavior of AISI 310 stainless steel and high-chromium cast steel (Fe-27 wt.% Cr) was studied over the sulfur-pressure range of 10-3 ~1 atm. at 700-900℃. The sulfidation kinetics of both alloys followed the parabolic rate law and the sulfidation rate constants increased with increasing temperature and sulfur pressure. The variation of the parabolic rate constants related to sulfur pressures is fit to the relationship of Kp~(const.) PS21/n, where n=5.8~6.7 for AISI 310 stainless steel and n=2.2~2.8 for high-chromium cast steel. The scales formed on both alloys were duplex and multilayered. The outer scale of 310 stainless steel consisted of mostly (Fe,Ni)9S8, FeS/Fe1-xS and minor Cr2S3/Cr3S4, while the inner layer consisted of Cr2S3, Cr3S4, NiCrS4 and FeS. The outer scale of high-chromium cast steel consisted of mostly iron sulfide (FeS/Fe1-xS) and minor chromium sulfide (Cr2S3/Cr3S4), while the inner layer was a heterophasic mixture of iron sulfide and chromium sulfide. Platinum-markers of both alloys were located at the interface between the inner and outer scales, suggesting that the outer scale grew by the outward transport of cations and the inner scale grew by the inward transport of sulfur.