合金元素與製程對Alloy 800H之耐蝕性質影響研究

Effect of Alloy Element and Process on the Corrosion Behaviors of Alloy 800H

本研究利用浸泡試驗，探討不同合金元素之添加以及精煉製程之差異，對Alloy 800H合金於水溶液腐蝕性質之影響。由不同溶液之浸泡試驗之結果顯示，Cr含量的增加有助於降低Alloy 800H於低濃度HCl溶液中之腐蝕速率；Cu的增加，可大幅提升於屬於還原性酸之H2SO4溶液中之耐蝕性質；而在屬於氧化性酸之HNO3，以及鹼性之NaOH環境中，Alloy 800H均擁有極佳之耐蝕性質。而於ASTM G36沸騰42% MgCl2之應力腐蝕斷裂敏感性評估試驗中，則可發現到經VIM（Vacunn Induction Melting） + ESR（Electro-Slag Remelting）精煉製程之Alloy 800H合金，其抗應力腐蝕破裂能力遠高於傳統經EAF（Electric Arc Furnace）電爐製程之Alloy 800H，推測其原因與精煉製程後，合金內之偏析現象及析出物數量較少有關。

Effect of alloying element and process parameter on corrosion behaviors of Alloy 800H in different solutions is evaluated by using the immersion tests. The experimental results show that Alloy 800H with higher Cr addition owns lower corrosion rate in low concentration HCl solution. With higher Cu adding, the corrosion behavior is enhanced in sulfuric acid. However, in nitric acid and sodium hydroxide solution, all the Alloy 800H, whatever chemical composition difference, have the excellent corrosion behaviors. Additional, the stress corrosion cracking (SCC) susceptibility of Alloy 800H with vacuum induction melting (VIM) + electro slag remelting (ESR) process is much lower than that just with electric arc furnace (EAF) process. It might be due to a low segregation degree and the fewer precipitate within substrate after remelting process.