Study on wear and friction resistance of nanocrystalline Fe nitrided at low temperature

A nanocrystalline surface layer was fabricated on a pure Fe plate by means of a surface mechanical attrition treatment (SMAT). The SMAT process is able to enhance gas nitriding kinetics so that a nanostructured nitride layer can be formed at low nitriding temperature. Nanoindentation measurements indicate that the hardness value of the nitrided SMAT sample is about 6.1 GPa at the top surface, and decreases gradually to about 2.0 GPa in the matrix. Nanoscratch tests show that the friction coefficient decreases and the wear resistance increases with the SMAT sample. The improvement in friction and wear properties may be attributed to the higher hardness in nanocrystalline nitride layer.