Machinability Characterization of P/M Materials

An instrumented bench test has been developed to evaluate the machinability performance of P/M materials. The set-up consists of a high power press drill with automatic feed rate control coupled with a specially designed specimen holder which allows the monitoring of the torque applied on the cutting tool and the thrust transmitted to the test specimen. The feed rate and the rotating speed are also continuously recorded. All four variables, measured nine times per second, are transmitted to a data acquisition system and then to a computer for analysis. The changes in thrust force and torque during drilling are then related to tool wear which is evaluated by microscopic techniques. Two case studies are presented. In the first one, the machinability of forged FC-0205 specimens containing various types of MnS was compared; the high sensitivity of the bench test permitted to measure the effect of the various types of MnS powders on the machinability behavior of the materials. In the second study, the effectiveness of hexagonal boron nitride as machinability enhancer was confirmed. In both cases, an increase of tool wear was correlated to the measurement of higher thrust force and torque on the drill.