Corrosion behavior of FBR structural materials in high temperature supercritical carbon dioxide

高温超臨界CO中における高速炉構造材の腐食挙動

古川 智弘  ; 稲垣 嘉之; 有冨 正憲*

Furukawa, Tomohiro; Inagaki, Yoshiyuki; Aritomi, Masanori*

高クロムマルテンサイト鋼(12Cr鋼)及び高速炉構造用316鋼(316FR)を対象に20MPa, 400-600Cの超臨界CO中にて腐食試験を実施した。両鋼の2000h浸漬材において、高温酸化が観察された。12Cr鋼の場合、各温度において放物線型の重量増加挙動が観察され、アレニウス型の酸化速度評価式でこれを定式化することができた。鋼表面には2層構造の酸化スケールに覆われていた。316FRの重量増加は12Cr鋼に比べて極わずかであり、12Cr鋼でみられた温度・時間依存性は観察されなかった。鋼表面には、ノジュール状の酸化物が観察された。また、ブレイクアウェイ酸化や延性の低下を招く浸炭が両鋼には観察された。

Corrosion test of high-chromium martensitic steel (12Cr-steel) and FBR grade type 316 stainless steel (316FR) were performed at 400-600 C in supercritical CO pressurized at 20MPa. High temperature oxidation was measured up to approximately 2000h in both steels. In the case of 12Cr-steel, the weight gain showed parabolic growth with exposure time at each temperature. The oxidation coefficient could be estimated by the Arrhenius function. The specimens were covered by two successive oxide layers. In the case of 316FR specimens, the weight gain was significantly lower than that of 12Cr-steel. Dependency of neither temperature nor exposed time on oxidation was not observed. Nodule shape oxides were observed on the surface of the 316FR specimen. Carburizing, known as a factor in the occurrence of breakaway corrosion and/or the degradation of ductility, was observed on the surface of both steels.