The behaviour of DLC under high mechanical and thermal load

Abstract

Hydrogenated amorphous diamond-like carbon (DLC) and silicon doped DLC (Si-DLC) in comparison with other low wear friction coatings and commonly used lubricants were tested in a compression-spin test in order to determine their suitability as substitutes for lubricants in warm massive forming with temperatures up to 700 °C. In the compression-spin test a coated, respectively, lubricated punch is pressed and simultaneously rotated in a steel sleeve. Characteristic value is the covered sliding distance, until the coefficient of friction matches a value of 0.3. The temperature was varied between room temperature and 700 °C, the rotating speed between 10 and 50 rev./min. At low temperatures up to 300 °C lubricants containing molybdenum disulfide show the best results. Also, the sputtered MoS 2 coating is very good at low temperatures. DLC presents the best performance of all tested coatings and lubricants at 500 and 700 °C and is good at lower temperatures. Si-DLC seems to be only suitable at a temperature of 700 °C under the presented load conditions. The covered sliding distance grows for all tested coatings with increasing rotating speed at room temperature.