本研究底材使用低碳鋼，分別經包覆擴散滲鐵鋁及熱浸鍍鋁，於 750 ℃ 進行高溫空氣及沉積 NaCl/Na2SO4 高溫熱腐蝕潛變試驗，探討潛變特性。研究結果顯示，滲鐵鋁之外鋁化層及內鋁化層分別為延性 FeAl 相及 Fe3Al 相，熱浸鍍鋁之外鋁化層及內鋁化層則分別為 Al + FeAl3 相及硬脆之 Fe2Al5 相。於 750 ℃ 高溫擴散後，滲鐵鋁之外鋁化層及內鋁化層仍為 FeAl 相及 Fe3Al 相；熱浸鍍鋁之外鋁化層及內鋁化層轉變為 Fe2Al5 + FeAl2 相及 FeAl 相。熱浸鍍鋁於相轉變過程，因鐵原子擴散速度較鋁原子快，於塗層中生成 Kirkendall 孔洞。高溫及熱腐蝕潛變結果顯示，由於熱浸鍍鋁塗層相較於滲鐵鋁塗層較厚，能更有效地保護底材，因此熱浸鍍鋁壽命皆高於滲鐵鋁。由於滲鐵鋁之 FeAl 相及 Fe3Al 相為延性相且與底材相容性較好，而熱浸鍍鋁之 Fe2Al5 相及 FeAl2 相為脆性相，加上塗層中有許多孔洞，以致滲鐵鋁伸長率皆大於熱浸鍍鋁。結果顯示，經兩種鋁化處理後生成之保護性之鋁化層於高溫環境能有效提升低碳鋼底材抗氧化能力，並延緩底材受腐蝕鹽之侵蝕。

The creep properties of the low-carbon steel and its aluminized counterparts with the pack cementation (PC) and hot dipped aluminum (HDA) treatments were studied in dry air and in NaCl/Na2SO4 hot-corrosion environments at 750 ℃. Duplex ductile aluminized-layers of the inner Fe3Al and the outer FeAl formed on the PC samples, while those of the inner Fe2Al5 and the outer Al and FeAl3 were observed on the HDA samples. The PC samples retained unchanged structures after high-temperature diffusion at 750 ℃, however, those changed to the inner FeAl and the outer Fe2Al5 and FeAl2. The phase transformation of HDA samples was due mainly to faster transports of iron atoms with respect to those of aluminum ones, which in turn resulted in forming Kirkendall pores in the HDA coatings. It was found that HDA samples revealed thicker coating layers, which provided a better protection for the carbon-steel substrate, leading to a higher creep lifetime, as compared with PC samples. On the other hands, by forming stable FeAl and Fe3Al layers on PC samples, which served as ductile phases to the carbon-steel, which provided a better elongation value with respect to HD samples, in which brittle Fe2Al5 and FeAl2 phases have Kirkendall pores. In summary, both PC and HDA treatments could give much better oxidation-resistance for the carbon-steel substrate, which in turn resulted in a reduction of the hot-corrosion attack.

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