Growth of α-Al2O3 layer involving abnormal oxides in FeCrAl alloy tube fabricated by WEDM process and electrical insulating performance in fusion reactor blanket

The tubular specimens of FeCrAl alloy APMT (Fe-22Cr-5Al-3Mo) were fabricated by a wire electrical discharge machining (WEDM) process. The oxidation characteristics of the machined surface were investigated by means of the oxidation tests performed in air atmosphere at the temperatures of 1273 K and 1373 K up to 100 h. The abnormal oxides such as CuAl 2 O 4 and ZnAl 2 O 4 were grew on the recast layer which was locally remained on the machined surface even after the mechanical polishing procedure. The α-Al 2 O 3 layer involving the abnormal oxides was formed on the machined surface in the oxidation treatment at 1273 K for 10 h. The apparent electrical conductivity of the layer involving the abnormal oxides was larger than that without the abnormal oxides. Thick Al-rich oxide layer was formed under the abnormal oxides when the oxidation treatment was performed at 1373 K. The apparent electrical conductivity of the oxide layer became lower due to the presence of the thick Al-rich oxide. This oxide layer formed at 1373 K could function as an electrical insulating layer to reduce the magnetohydrodynamic pressure drop in liquid breeder blanket systems of magnetic confinement fusion reactors. • Microstructure of recast layer formed by WEDM process on surface of FeCrAl alloy. • Formation behavior of α-Al2O3 layer involving abnormal oxides around recast layer. • Apparent electrical conductivity of α-Al2O3 layer involving abnormal oxides. • Oxidation at 1373 K to promote Al-rich layer formation under abnormal oxides. • Reduction of MHD pressure drop by α-Al2O3 layer involving abnormal oxides.