Worm gears are a type of helical gearboxes with intersecting wheel axles which are characterized by high transmission ratios and particularly low noise operation due to the continuous contact of teeth. In addition to the rolling process a remarkable sliding movement takes place in the contact zone and thus requires special demands on the tribological behavior of the contact partners. Therefore abradable bronze is usually used as sliding and wear material for worm wheels in combination with hardened steel for worms. The motivation of this study is the substitution of bronze by steel materials combined with the advantages of an efficiency increase which is here interpreted as increase in power density or efficiency factor. This paper focuses on wear mechanisms of tribomutation in the contact and edge zone of the steel tooth. For this purpose wear tests on worm wheels of different steel alloys in various manufacturing variants were investigated. In addition to the classical visual examination an analysis procedure for systematic evaluation of contact and edge zones was developed, consisting of sample preparation, metallography and analyzes on nanometer scales using AFM (atomic force microscope). The results of the macro- and microscopic investigations were transferred to specially defined wear characteristics. The local, precise description of the wear area allows a comparison between surface and structural changes due to the wear process. In addition, the correlation between the failure torque and the wear of individual worm wheels was discussed. Metallurgical effects of varying extents could be detected in the edge zones of all test specimens. The AFM has proven to be a functional and versatile addition to metallography for detailed investigations of these edge zone changes. The results of this study permit a qualified assessment of the tested steel worm wheels.