Tribological Behaviour of the Diamond/Steel Couple: Influence of the Temperature

With its excellent mechanical and chemical properties, diamond is expected to find many applications in industrial and engineering fields, and more particularly for the machining process, where the use of diamond coated tools leads to an improvement of their efficiency as well as an increase of the tools lifetime. A better understanding of the tribological behaviour of diamond coatings represents then a considerable stake. Intrinsic characteristics like the crystals orientation or the coatings thickness, have a great influence on the tribological properties of this kind of films. But the way the diamond coatings are used also plays an important part on their friction and wear behaviour: the nature of the counterface, the environment, or the variations of the applied normal load induce modifications of the physico-chemical properties of these coatings. The aim of this work is to study the influence of one of these experimental parameters, on the diamond tribological behaviour: the surrounding temperature. Friction tests were then realised at various temperatures with the diamond (obtained by flame process)/HSS couple, under different normal loads. It was shown that the diamond coatings and the discs tracks were significantly modified when increasing the temperature; both the friction mechanisms and the transfer were greatly dependent on the temperature of the environment. The sliding surfaces of the diamond coating and of the HSS disc were observed by Scanning Electron Microscopy and analysed by Energy Dispersive Spectroscopy and Raman spectroscopy to study the sight and the composition of the transferred layer as well as of the friction areas.