GRAIN-REFINEMENT AND HYDROGEN EMBRITTLEMENT IN IRON ALUMINIDE ALLOY FA129

Iron aluminides are susceptible to hydrogen cold cracking during gas t ungsten are welding. Fine grained base materials have been shown to be mole resistant to environmental embrittlement when tested in the pres ence of water vapour than coarse grained base materials. To study the effect effusion zone gi ain size on cold cracking susceptibility, weld s were produced using magnetic are oscillation to refine the fusion zo ne grain structures. Tensile tests were conducted in varying water vap our atmospheres, on weldments with average fusion zone grain sizes ran ging between 115 and 530 mu m. Fracture strength data followed Nail-Fe tch behaviour and the effect of water vapour concentration was also in corporated into the traditional plot. The results of the tensile tests showed the finer grain size fusion zones were less susceptible to hyd rogen cracking and more tolerant of high hydrogen concentration than c oarse fusion zone gain structures.