Investigation of the Influence of Different Hard Coatings on Chip Formation and Process Forces When Machining Duplex Steel 1.4462

Abstract

When machining duplex steel 1.4462 the choice of the hard coating of the cutting tool plays a major role due to the high process temperatures, caused by relatively low thermal conductivity of this material. Hard coatings can have different thermo-physical properties, e. g. thermal conductivity and specific heat capacity. Thus, they influence the process temperatures in the shear zones and have an impact on the chip formation. For a mechanisms-oriented tool development it is necessary to understand these influences. Experimental cutting tests based on a linearorthogonal kinematic are a suitable method for an experimental approach. A challenge with experimental methods is to vary the thermo-physical properties of the coatings without changing the friction effects in the contact areas of the tool and workpiece at the same time. An unwanted change of the friction leads to superimposed effects and difficulties during the interpretation of the influence of the thermo-physical properties. This work discusses the influence of two different wear protection layers on the behavior of an austenitic-ferritic duplex steel during linearorthogonal cutting experiments. In the investigations, one monolayer coating (TiAlN) and one multilayer coating (TiN-TiCN-Al2O3) were examined. The experiments were carried out under different cutting conditions and wear conditions of the tools to generate various friction conditions. In the results analysis, focus is mainly given to the cutting and feed forces as well as the chip thickness values. The experimental results are supplemented with analytical analyses to understand the influence of thermo-physical properties of coatings and interfacial effects caused by friction.

Keywords: Hard coating; Thermo-physical properties; Thermal conductivity; Hot hardness; Linear-orthogonal cutting; Chip formation; Process forces; Wear; Friction; Duplex steel