THE LIQUID-METAL EMBRITTLEMENT OF IRON AND FERRITIC STEELS IN SODIUM

The liquid metal embrittlement of iron and A508 III, 2 1/4Cr-1Mo and 1 5Mo3 steels in sodium at 200-400 degrees C has been studied, using dyn amic straining at 10(-6) s(-1), in order to investigate the roles of m icrostructure and composition. The steels comprised bainitic, martensi tic, tempered martensitic and ferritic/pearlitic microstructures. All materials were embrittled by sodium, the embrittlement being associate d generally with quasicleavage on fracture surfaces. Intergranular cra cking was also found with martensitic and ferritic/pearlitic microstru ctures. The susceptibility to embrittlement was greater in higher stre ngth materials and at higher temperatures. The embrittlement was simil ar to that encountered previously in 9Cr steel, which depends upon the presence of non-metallic impurities in the sodium.