The oxygen-dispersion-strengthened FeAl Grade 3 intermetallic alloy has undergone a low energy-high flux nitridation treatment. The uniform implanted layer is accompanied by a random distribution of protrusions anchored by yttria particles. Electron microscopy studies reveal the presence of a thin layer of AlN embedded in a matrix of FeAl, which mainly accounts for the dramatic increase in surface microhardness. After nitridation, fragmentation of the outermost FeAl grains occurs through which countercurrent diffusion of nitrogen and aluminium seems to occur. As a result, segregation of alpha-Fe is observed at the nitrided layer/substrate interface. (C) 2004 Elsevier B.V. All rights reserved.