Corrosion behaviors of iron-base alloy, nickel-base alloy and refractory metal alloys in high-temperature impure helium gas

The corrosion behaviors of SUS 316, PE 16, Nb-1%Zr, V-25%Mo, Mo and TZM in the He containing O2 of 0.1 vpm and N2 of 5 vpm at temperatures from 700 to 1,0000C were studied. The intergranular oxidation was observed for SUS 316 and PE 16 in the range of test temperatures. The rate of intergranular oxidation obeyed parabolic rate law and it is estimated that oxygen diffusion in the metal determined the penetration rate. Nb-1%Zr and V-25%Mo extremely absorbed oxygen and nitrogen from the atmosphere at test temperatures. The oxygen content of TZM also increased with time of exposure. The absorption rate of nitrogen in Nb-1%Zr and oxygen in TZM can be explained with the adsorption model of the active gas on the metal surface. Molybdenum did not show any change in microhardness, oxygen and nitrogen contents and microstructure after exposure to He at temperatures from 700 to 1,0000C. (author)