Understanding the Effect of W and Mo on the Liquid Metal Compatibility of Ferritic/Martensitic Steels: A Predictive Study

Considering the high energy neutron environment in a nuclear fusion reactor, Reduced Activation type Ferritic/Martensitic Steels (RAFMS) containing tungsten, have been carefully curated from their surrogate Cr–Mo type Ferritic/Martensitic Steels (FMS). The substitution of molybdenum by tungsten improved the radiation stability and mechanical characteristics RAFMS. However, the effect of tungsten on the liquid metal corrosion resistance of FMS has not been well investigated. The current work attempts to estimate liquid metal compatibility by examining the surface oxides of Indian RAFMS (IN RAFMS) and its surrogate steel, P91 (9Cr-1Mo), using X-ray Photoelectron Spectroscopy. Subsequently, thermodynamic calculations have been used to establish the stability of such oxides in both ambient circumstances and liquid lead–lithium eutectic alloy (Pb–Li). The results showed that tungsten can provide a higher resistance to liquid metal attack than molybdenum because its oxides are more stable. Actual corrosion experiments with IN RAFMS and P91 were performed in liquid Pb–Li for a durations upto 2000 h, successfully validating the above stated prediction.