披覆含鉻質硬層之Fe-Mn-Al合金鋼耐蝕性研究

The Corrosion Resistance of the Chromium Containing Hard Coating on Fe-Mn-Al Alloy Steel

本研究採用固體滲鉻法在Fe-30.6Mn-6.8Al-0.9C的合金鋼試片表面披覆生成碳化鉻等含鉻質之硬質層，以25℃，3.5wt%氯化鈉水溶液的電化學測試來鑑定鉻質硬層的常溫抗蝕性，以877℃的10% NaCl與90% Na2SO4混合熔融鹽之高溫熱腐蝕試驗來判斷含鉻硬質層的高溫抗氧化性質。由試驗結果發現，固體滲鉻處理的試片表面生成(Fe,Cr)2 N1-x與Cr23C6相，較內層則主要是Cr7C3相。整體而言，固體滲鉻處理使得鐵錳鋁合金鋼基材的抗蝕性顯著提高，在25 ℃，3.5wt%氯化鈉水溶液有極優良的抗蝕性，對於高溫熔融鹽熱腐蝕之抵抗性亦優於傳統430不銹鋼，不過滲鉻表面的緻密性與氧化物缺陷是影響鐵錳鋁合金鋼抗蝕性的重要因素。

Fe-30.6Mn-6.8Al-0.9C alloy steel is employed in this study to coat the chromium carbide and related hard coatings on the surface by using pack chromization process. Electrochemical test in 25 ,3.5wt% aqueous solution is used to evaluate the corrosion resistance of chromized specimen in room temperature. The immersion test in 10 wt NaCl 90 wt Na2SO4 mixed molten salt at 877℃ for 48 hours is conducted to investigate the hot corrosion resistance of chromized specimen. The (Fe,Cr)2 N1-x and Cr23C6 phases are found on the chromized surface, while the internal part of chromized layer is Cr7C3 phase. In general, the corrosion resistance of the chromized specimen is apparently improved. The resistance to high temperature mixed molten salt of the chromized specimen is also better than that of 430 stainless steel. However, the corrosion resistance of the chromized Fe-Mn-Al alloy steel will be affected by denseness and oxide defects in the chromized layer.