| Summary: | The lubricant behaviour at elevated temperatures was investigated by conducting pin-on-disc tests between P20 tool steel and AA7075 aluminium alloy. The evolutions of coefficient of friction (COF) at elevated temperatures showed three distinct stages: stage I (low friction stage), in which boundary lubrication was prevalent and the coefficient of friction was low; stage II (transient stage), in which the lubricant film thickness decreased to a critical value and the coefficient of friction increased rapidly; and stage III (breakdown stage), in which the lubricant was completely removed from the interface and the coefficient of friction was equal to its value under dry sliding conditions. In the present work, 2 types of water-graphite based lubricants were studied by pin-on-disc tests under different contact conditions. The effects of tooling and workpiece temperature determined from the experimental results were investigated in this paper and a comparison with an oil-graphite based lubricant was conducted.
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