Resumo

ABREU, C.S. et al. Revestimentos de diamante CVD em Si₃N₄: Atrito e desgaste no deslizamento de pares próprios sem lubrificação. C.Tecn. Mat. [online]. 2006, vol.18, n.1-2, pp.27-34. ISSN 0870-8312.

Due to its extreme hardness natural diamond posses a high wear resistance. However, apart from the high cost, it is characterised by a strong anisotropy in terms of tribological behaviour. These limitations are overcome using diamond coatings produced by chemical vapour deposition (CVD) which due to their polycristalline nature, while retaining the extreme properties of natural diamond, make surfaces with high tribological performance. CVD diamond coatings can be deposited on various types of substrates. However, in order to sustain high levels of adhesion, silicon nitride (Si₃N₄) based ceramics constitute a particularly attractive substrate material due to its carburizing nature and low thermal expansion coefficient mismatch with diamond. In the present work, dense Si₃N₄ samples were diamond coated using the microwave plasma activated chemical vapour deposition (MPCVD) technique. The tribological tests were performed using a ball-on-flat (BOF) configuration on self-mated diamond CVD pairs, without the presence of lubrication in ambient atmosphere. The applied normal varied in the range 10-80 N, while keeping the frequency (1 Hz) constant throughout the tests. The tribological behaviour was characterised by extremely low steady-state friction coefficient values (f ~ 0.03-0.04), accompanied by wear rates denoting a very mild to mild wear regime (10^-8£ K £ 10^-7 mm³N^-1m^-1). The main wear mechanism consisted on the truncating of diamond crystals parallel to the plane of sliding, resulting in a self-polishing of the interacting surfaces at the micro-scale level.

Palavras-chave : CVD diamond; Silicon nitride; Friction; Wear.

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