Phase Composition and Tribological Characteristics of the Surface Layers of Carbon Tool Steels after Laser Processing in Air

Abstract

Abstract We present the results of studies of the phase composition of an oxide layer formed on the surface of U8 and U10 carbon tool steels after laser treatment in air using a quasi-continuous laser source. Data on the structure of the oxide–metal interfaces are obtained by X-ray photoelectron spectroscopy using the Al K α1,2 line; the SPECS surface analysis system is applied. The thickness of the completely oxidized surface layers is 38.7 and 99.0 nm, respectively, for steels U8 and U10. The thickness of the transition layer (81.0 nm) located at the interface with unmodified bulk steel and consisting of iron oxide FeO and iron atoms for U10 steel is approximately two times smaller than that for U8 steel. We determine the composition of the oxides on the surface of the steels after laser processing. The surface of U8 steel is mainly a wustite film, the presence of which determines the poor wear characteristics of the surface of the laser-action zone. On the contrary, the thicker oxide layer of modified U10 steel containing Fe 2 O 3 and Fe 3 O 4 with better strength characteristics ensures a higher wear resistance of the U10 steel surface after laser processing during tribological tests. For U10 steel, the wear rate of the modified surface is more than halved, while for U8 steel, this figure is only ~17%.