In this study, the morphological, structural and chemical changes during friction loading of a metastable fully austenitic TWIP steel and of a case-hardened carburized 16MnCr5 steel were investigated by various methods. To do so, EFTEM imaging, SAD, TEM-XEDS, TEM-EELS, XRD, EBSD, and ACOM-TEM were applied for the unloaded state and after defined friction loading. Although the investigated materials appeared very different in their unloaded states concerning their phase compositions, grain sizes and mechanical properties, the friction loading led to significant, but comparable changes in both materials. These changes start immediately from the worn surface and continue towards the sample depth. An extremely fine-grained nanocrystalline surface layer with a thickness of several hundred nanometers and a nanocrystalline sub-surface layer were formed with sharp interfaces between them. The grain size remains nearly constant within the first layer, but increased immediately crossing the interface between these layers and gradually enlarges further within the sub-surface layer with increasing distance to the interface. These layers differ tremendously from the unloaded states and were characterized in a detailed way. Explanations for the formation of these layers were supposed.