Abstract
Surface integrity is important factor for components exposed to wear, like cold working tools, which need to possess high hardness combined with high wear resistance. Surface treatments such as grinding, hard turning, and hard turning with slide burnishing have been developed for its improvement. Vancron 40 and Vanadis 8 tool steels, of different chemical composition and different types and amounts of carbides, were now investigated. Heat treatment was carried out in vacuum furnaces with gas quenching to hardness of Vancron 64 ± 1 HRC and of Vanadis 65 ± 1 HRC. 3D topography, optical and scanning electron microscopy, X-ray diffraction and ball-on-disc tribological tests against Al2O3 and 100Cr6 balls as counterparts were used to examine wear and friction. For both steels, the lowest values of dynamic frictions and wear rates against Al2O3 counterbodies were achieved after sequential process of hard turning with slide burnishing with a burnishing force of 180 N. For alumina balls, the increase of wear resistance, achieved after hard turning plus burnishing in comparison to grinding exceeds 50 and 60%, respectively for Vanadis 8 and Vancron 40 steels.
Highlights
Cold working processes are widely used, among others in mass production of automotive parts, which are required to possess high strength
The biggest differences were for Sz parameter, which characterizes the height of the greatest amplitude of the surface, and is the most sensitive to its changes.Very similar trend was found for material volume (Vmc) in roughness core, for which the highest values were determined after T + B150 and T + B180 treatments, respectively for Vanadis 8 and Vancron 40 steels
Our results show that the parameters related to the material ratio curve, including the volume parameters, can be successfully correlated with the coefficient of friction and wear resistance for surfaces after sequential processing
Summary
Cold working processes are widely used, among others in mass production of automotive parts, which are required to possess high strength. Of particular concern of designers and tools technologists are components subjected to high surface pressures under unfavourable conditions of boundary friction (Kleiner et al, 2003; Klocke, 2013; Hutchings and Shipway, 2017). The deterioration of the performance of tools for cold working generally takes place as a result of progressive tribological wear during operation. The catastrophic (dynamic) wear, which can include, chipping of tool edge when the ultimate strength is locally exceeded, or component fatigue failure, may be limited by a careful choice of tool material. Surface engineering becomes important because cold-working tools are exposed to very high contact stresses occurring during forming and deformation of the workpiece material. The state of technological surface layer (TSL) of tools affects significantly their life (Dearnley, 2017; Burakowski and Wierzchoń, 1999)
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