Corrosion Behavior of Superalloys in High Temperature Gas Cooled Reactor in Impure Helium With Corrosion Time

There are trace impurities such as CO, CH₄, H₂, H₂O in helium of main cooling loop of high temperature gas cooled reactor, which will cause corrosion of superalloy materials used in steam generator and intermediate heat exchanger at high temperature. Previous experiments and literatures show that the formation of chromium rich protective oxide layer on the surface of superalloy is an important factor to prevent severe corrosion of superalloy. In this paper, the corrosion tests of four candidate materials Inconel 617, Incoloy 800H, Hastelloy X and T-22 for high temperature reactor steam generator were carried out. The four superalloys were exposed at 950 °C for 50, 100, 150 and 200 hours in helium with a certain impurity content. The corrosion results were analyzed by weighing, scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The corrosion of these four alloys occurred in different degrees. In this paper, we mainly analyse the conclusion of 50h and 200h corrosion of these four kinds of superalloys. On the whole, Hastelloy X and T-22 have good corrosion resistance and low mass gain; Inconel 617 and Incoloy 800H have poor corrosion resistance, obvious internal oxidation and high mass gain.