Comparison between nanophase formation during friction induced surface wear and mechanical attrition of a pearlitic steel

The surfaces of steel railroad tracks experience wear-induced hardening within a surface layer more than 100 mu m in thickness. The grain size is reduced to 15 - 20 nm, resulting in an increase of Vickers hardness by a factor of four, as determined by nanoindentation measurements. For comparison, the microstructure of mechanically alloyed powder samples is found to be similar to those of the wear-induced surface layer. As such, the ball Milled powder samples can be used as a model system for characterizing the chemical, mechanical (hardness, Young's modulus, coefficient of friction) and thermal properties of the wear induced nanophase surfaces.