Study of the wear behaviour of diamond-like coatings at elevated temperatures

The wear behaviour of a-C:H coatings in ambient air up to maximum temperatures of 300 °C is reported. A simultaneous tribological and thermal load was imposed using a low-amplitude oscillatory sliding test in combination with a heatable specimen holder. The investigation showed that the tribological behaviour of the a-C:H coatings changed considerably at elevated temperatures: the coefficient of friction decreased and the wear scars became larger and deeper, indicating a more severe wear process at elevated temperatures. Under the present test conditions tribological behaviour started to change around 100 °C. On previously annealed samples, however, the wear properties at room temperature remained stable up to annealing temperatures of 300 °C. The temperature dependent wear behaviour of diamond-like carbon has been linked to the surface properties of these materials which become modified at relatively low temperatures where bulk properties are known to remain unchanged.