Effects of oxidation on the deuterium permeation behavior of the SIMP steel

Reduced activation ferritic/martensitic (RAFM) steels are the primary candidate structure materials for the blanket in future fusion power plants. In the recent years, a novel 9-12 % Cr modified F/M steel named SIMP steel has been developed. The deuterium permeation behavior of the SIMP steel with and without oxide layer has been evaluated using a gas driven permeation (GDP) device. The permeability of original and oxidized SIMP steel has been derived and compared. In order to characterize the oxide layer, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS) experiments have been carried out. GDP results show that the SIMP steel has similar deuterium permeability with the CLF-1 steel. The deuterium permeability of the oxidized SIMP steel is lower than that of the original SIMP steel. Heat treatment during the oxidization process has no influence on the deuterium permeability of the bare SIMP steel. The cross-section SEM pictures present that with the increase of the oxidation time, the thickness of the oxide layer is increased. The oxide layers are observed to be porous. The results of XRD and EDS show that the oxide layer mainly consists of chromium oxide and accumulation of chromium can be detected in the surface region. The formation of the chromium oxide in the surface of the SIMP steel could be the reason of the decrease of the deuterium permeability of the oxidized SIMP steel.

低活化铁素体/马氏体钢（Reduced activation ferritic/martensitic, RAFM）是未来聚变堆包层的首选结构材料。近年来，一种新型9-12%铬改性铁素体/马氏体（ferritic/martensitic, F/M）钢SIMP钢已被研发成功。采用气体驱动渗透（gas driven permeation, GDP）装置对有无氧化层的SIMP钢的氘渗透行为进行了测试评估，推导并对比了原始态与氧化态SIMP钢的氘渗透系数。为表征该氧化层，开展了X射线衍射（X-Ray Diffraction, XRD）、扫描电子显微镜（Scanning Electron Microscopy, SEM）以及能量色散X射线光谱（Energy-Dispersive X-ray Spectroscopy, EDS）测试。气体驱动渗透测试结果表明，SIMP钢的氘渗透系数与CLF-1钢相近；氧化态SIMP钢的氘渗透系数低于原始态SIMP钢。氧化过程中的热处理对未包覆氧化层的裸SIMP钢的氘渗透系数无显著影响。截面SEM图像显示，随着氧化时间延长，氧化层厚度逐渐增加，且观测到该氧化层呈多孔结构。XRD与EDS测试结果表明，氧化层主要由氧化铬组成，且在表层区域可检测到铬元素富集。SIMP钢表面氧化铬的生成，可能是导致氧化态SIMP钢氘渗透系数降低的主要原因。