Impact of the Heat Treatment Condition of Steel AISI 4140 on Its Frictional Contact Behavior in Dry Metal Cutting

Abstract

In this work, the impact of the heat treatment condition of steel AISI 4140 on its frictional contact behavior with coated cemented carbide and cubic boron nitride (CBN) in dry metal cutting is experimentally investigated. Two different kinds of tests were performed. The frictional behavior was investigated under conditions very similar to metal cutting on a frictional test bench, which was installed on a broaching machine. Additionally, orthogonal cutting processes with linear workpiece geometries were conducted on the same machine. The cutting experiments included observations of cutting forces, high-speed filming of chip formation, chip thickness ratio analysis as well as a comprehensive metallographic characterization of the chips and workpiece surfaces. The impacts of the undeformed chip thickness and cutting speed were investigated individually for coated cemented carbide and CBN as cutting materials. The frictional examinations delivered the Coulomb friction coefficients for all four combinations of work and cutting materials as a function of the relative velocity. The identified frictional behaviors explain the dependencies of forces, chip thicknesses, and surface microstructures on the tool and process conditions during the cutting tests.