鉬鋁及鋁矽鍍層對310耐熱鋼抗高溫硫化腐蝕之影響

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

本研究探討表面鍍鉬鋁（含純鉬、Mo-20及-32at.% Al）、鋁矽（Al-7wt.% Si）合金鍍層及預氧化處理鋁矽鍍層之AISI 310耐熱鋼，於硫分壓10-1大氣壓，溫度700~900℃下的高溫硫化行為。鉬鋁及鋁矽鍍層分別是以射頻磁控濺鍍法及熱浸鍍法鍍上。實驗結果顯示，鉬鋁及鋁矽合金鍍層皆可降低310耐熱鋼的硫化腐蝕速率。所有含鍍層之耐熱鋼的腐蝕動力學皆遵守拋物線型定律，且腐蝕速率常數隨著溫度上升而增快。含鉬鋁鍍層耐熱鋼的表面，腐蝕後生成二層硫化層，其中，外層主要是硫化鐵（FeS/Fe1-xS）、硫化鉻（Cr2S3/Cr3S4）、及少量的硫化鐵鎳 (Fe,Ni)9S8；內層為硫化鐵、硫化鉻、硫化鉬（MoS2），及少量的硫化鋁（Al2s3）、硫化鐵鉬（Fe1.25Mo6S7.7）和硫化鋁鉬（Al0.55Mo2S4）。含鋁矽鍍層耐熱鋼的表面，腐蝕產物主要為硫化鋁（Al2S3），及少量的硫化鐵（FeS8Fe1-xS）、硫化鉻（Cr2S3/Cr3S4）、硫化鐵鎳 (Fe,Ni)9S8。經預氧化處理含鋁矽鍍層之不鏽鋼，腐蝕後生成不同的氧化及硫化物；其中，氧化生成物為氧化鋁（Al2O3）、氧化矽（SiO2）及氧化鋁矽（Al2SiO5），硫化物則為硫化鋁及微量的硫化鐵、硫化鉻和硫化鐵鎳。

High-temperature sulfidation of AISI 310 heat-resistant steel coated with Mo-Al (containing pure Mo, Mo-20, or Mo-32at.% Al) and Al-7wt%Si (without or with preoxidation treatment) film was studied over the temperature range of 700 ~ 900℃ at 10-1atm. sulfur vapor. The Mo-Al and Al-Si coating was prepared by the R. F. magnetron sputter deposition and hot -dipping, respectively. The corrosion kinetics followed the parabolic rate law, and the sulfidation rate constants increased with increasing temperature in all cases. The scales formed on 310 heat-resistant steel coated with Mo-Al coating layer were duplex, consisting of an outer layer of mostly iron sulfide (FeS/Fe1-xS), Cr2S3/Cr3S4 and minor (Fe,Ni)9S8 and an inner complex scale of FeS/Fe1-xS, Cr2S3/Cr3S4, MoS2, and minor amounts of Al2S3, Fe1.25MO6S7.7, and Al0.55MO2S4. The scales formed on 310 heat-resistant steel coated with Al-Si coating layer were mostly consisted of aluminum sulfide (Al2S3), and minor amounts of FeS/Fe1-xS, Cr2S3/Cr3S4, and (Fe,Ni)9S8, while the scales formed on 310 heat-resistant steel coated with Al-Si coating with preoxidation treatment consisted of Al2O3, SiO2, Al2SiO5, Al2S3 and minor amounts of FeS/Fe1-xS, Cr2S3/Cr3S4, and (Fe,Ni)9S8.