Testing the Effectiveness of Hybrid Milling and Surface Burnishing in Improving the Wear Resistance of Machine Parts Made of Structural Steel

Due to the need to form a surface layer with specific operating properties, recent years have seen an increased interest in surface strengthening treatment, which aims to create a surface layer that improves the durability of parts. With a view to the economics of the machining process, it is common to combine shaping milling, characterised by high volumetric efficiency, with finishing burnishing, during which significant forces are applied. In the literature, one of the important limitations of such technological operations is the value of residual stresses, excessive values of which can lead to the flaking and falling off of surface fragments. In the present study, the authors put forward the research hypothesis that, in addition to stresses, the geometry of the machining roughness is also important and may contribute to faster tribological wear than stresses. It has been shown that what is important in hybrid machining is not so much the height of the resulting irregularities and the effectiveness of their levelling by burnishing, but the geometry of the irregularities. After milling, surfaces with small, regular irregularities with smooth peaks and shallow valleys were found to be the best in tribological tests. Such roughness can be plastically levelled out during burnishing. On the basis of the experimental studies carried out, it was shown that a higher burnishing force does not always lead to higher wear resistance.