Gaseous nitriding of iron with a nanostructured surface layer

A nanostructured surface layer was formed on a pure iron plate by means of surface mechanical attrition treatment (SMAT). It was found that a SMAT iron sample developed a nitrided layer twice as thick as that on a coarse-grained sample under the same gaseous nitriding conditions (500 °C for 2 h), which is attributed to the fast diffusion of nitrogen along grain boundaries in the nanostructured iron. The nitrided layer of SMAT sample exhibited a high hardness and an excellent wear resistance.