鉬鋁鍍層對純鐵及310耐熱鋼的高溫硫化腐蝕影響

Effect of Mo-Al Coating on High-Temperature Sulfidation of Pure Iron and 310 Heat-Resistant Steel

本研究主要探討純鐵及310耐熱鋼表面濺鍍鉬鋁鍍層(Mo-20at.% Al)，於硫分壓0.1大氣壓，溫度700℃ ~ 900℃下的高溫硫化行為。鉬鋁鍍層係以射頻磁控濺鍍法鍍上，鍍膜時基材溫度為200℃，鍍膜厚度約2 µm。研究結果顯示含鍍層之純鐵及310耐熱鋼的腐蝕動力學皆遵守拋物線型定律，且硫化速率常數隨著溫度上升而增快，但其硫化速率皆比原材的硫化速率降低1 ~ 2個數量級。硫化後含鍍層之純鐵及310耐熱鋼表面皆生成雙層硫化物，其中，含鍍層之純鐵外層為硫化鐵(FeS/Fe1-xS)；內層主要是硫化鐵(FeS/Fe1-xS)、硫化鉬(MoS2)及少量的硫化鋁(Al2S3)、Fe1.25Mo6S7.7 與Al0.55M2S4的混合相。含鍍層之310耐熱鋼外層為硫化鐵(FeS/Fe1-xS)、硫化鉻(Cr2S3/Cr3S4)及(Fe,Ni)9S8；而內層則為複雜的硫化鐵(FeS/Fe1-xS)、硫化鉻(Cr2S3/Cr3S4)、硫化鉬(MoS2)及少量的硫化鋁(Al2S3)、Fe1.25Mo6S7.7與Al0.55M2S4的混合相。硫化鋁(Al2S3)及Al0.55Mo2S4的生成，有效地降低了硫化腐蝕速率。

High-temperature sulfidation of pure iron and AISI 310 heat-resistant steel coated with a Mo-20at.% Al film was studied over the temperature range of 700 900℃ at 0.1 atm. sulfur vapor. The Mo-Al coating about 2 µm in thickness was prepared by the R. F. magnetron sputter deposition at 200℃. The corrosion kinetics followed the parabolic rate law，and the sulfidation rate constants increased with increasing temperature. The sulfidation rates were reduced by 1 ~ 2 orders of magnitude for both pure iron and 310 heat-resistant steel with coating. The scales formed on pure iron with the coating layer were bilayered in all cases，consisting of an outer layer of mostly iron sulfide (Fes or Fe1-xS ) and an inner complex scale of Fes，Fe1-xS，MoS2，and minor Al2S3，Fe1.23MO6S7.7，Al0.55MO2S4，while the scales formed on 310 heat-resistant steel with the coating layer consisted of an outer layer of iron sulfide (Fes or Fe1-xS)，Cr2S3 /Cr3S4 and minor (Fe,Ni)9S8 and an inner complex scale of FeS，Fe1-xS，MoS2，Cr2S3 /CrS4，and minor Al2S3，Fe1.25MO6S7.7，Al0.55MO2S4. The formation of Al2S3 and Al0.55MO2S4 is responsible for the reduction of the corrosion rates.