Tribometer-Based Quantifying of Friction in Metal Cutting

Abstract

<p>The objective of this research was the further development and characterization of a heavy load, high temperature pin on disc tribometer. The goal of performing this testing on the tribometer is to simulate realistic machining conditions experienced between a tool and workpiece ‘offline’ in order to reduce the number of real machining trials used to select a tool coating and subsequently optimize cutting parameters. This approach is based on the understanding that a change in the cutting speed can alter the tool-chip interface temperature profile, which can change the coefficient of friction (COF) between the tool and workpiece and impact the tool wear mechanisms and rate. Significant modifications were introduced to the tribometer to increase its functionality; a resistance welder was integrated into the setup, and a completely new, fully automated Graphical User Interface was designed using National Instruments Labview software to allow for more careful control of all interacting components and variables. Careful investigations were carried out to understand the sensitivity of COF measurements to various input parameters in order to gain increased confidence in the meaning of COF measurements. Finally, various tool and workpiece material pairs were tested from room temperature to upwards of 900°C near the pin-disc interface and efforts were made to correlate the resulting COF measurements with machining data in the form of tool life and cutting force measurement. This research contributes towards the goals of improving machinability in two ways: first, by screening potential surface engineering treatments on the basis of reduced friction under machining relevant conditions of elevated contact stress and temperature; and secondly, by generating temperature-dependent friction data for different tool and workpiece material pairs that can be used to improve FE simulations of metal cutting.</p>