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In-Situ Friction Monitoring of Self-Mated CVD Diamond Coatings Using Acoustic Emission

2006; Trans Tech Publications; Volume: 514-516; Linguagem: Inglês

10.4028/www.scientific.net/msf.514-516.749

1662-9760

C.S. Abreu, F.J. Oliveira, J.R. Gomes, Manuel Belmonte, A.J.S. Fernandes, R.F. Silva,

Force Microscopy Techniques and Applications

In-situ measurements of acoustic emission (AE) in self-mated tribological pairs of CVD diamond coated silicon nitride (Si3N4) were made with the purpose of investigating the relationship between AE signal and friction events. A good correlation is found between the energy dissipation/emission processes, therefore enabling the possibility of monitoring the different friction regimes occurring during the sliding contact of microcrystalline diamond (MCD) coatings. Deposition of MCD on flat and ball-shaped Si3N4 samples was accomplished using microwave plasma assisted chemical vapour deposition (MPCVD) with H2/CH4 gas mixtures. The friction behaviour of self-mated MCD coatings was assessed using a reciprocating ball-on-flat geometry. The tests were run in ambient atmosphere without lubrication, the frequency (1Hz) and stroke (6mm) were kept constant while the applied normal load varied in the range 10-80N. The microstructure, surface topography and roughness of the MCD coatings were characterised by SEM and AFM techniques. The diamond quality was assessed from micro-Raman spectroscopy. The friction evolution was characterised by a short running-in period where the main feature is a sharp peak reaching values as high as approximately 0.6 followed by a steady-state regime with very low values in the range 0.03-0.04.