Chemical vapour deposition by hot filament


The present invention relates to hot filament chemical vapour deposition process (CVD) to increase the surface properties of silicon nitride (Si3N4) by applying nanodiamond films. The nanometric size of grains, the chemical inertness and diamond intrinsic hardness, associated with excellent adhesion to silicon nitride, provide high wear resistance and low friction coefficient. The main objective is to manufacture cutting tools for hard-to-machine materials (metallic, polymeric or ceramic matrix composites, non-ferrous metallic alloys, graphite, wood derivatives) and components for wear applications (mechanical seals, dies). The nanocrystalline CVD diamond growth occurs under conditions of continuous renucleation of grains, resulting in low surface roughness coatings adequate for immediate use in those applications, thus eliminating the polishing step required in polycrystalline diamond.

Innovative aspects & main advantages

The invention consists in the improvement of the surface properties of silicon nitride (Si3N4) by depositing a nanodiamond film using the hot filament chemical vapour deposition (CVD) method. The nanometric morphology, chemical inertness and intrinsic hardness of diamond confer to the ceramic a high wear resistance and low friction coefficient, allowing its use in demanding tribological applications, namely in the absence of lubrication in contact with abrasive materials and chemically aggressive fluids.


Cutting tools for difficult-to-machine materials used in cutting-edge industries, namely: i) non-ferrous metallic alloys for aeronautic and automobile industries such as Al-Si alloys and composites; ii) highly abrasive green or pre-sintered ceramic and cermet materials such as WC-Co; iii) glass fibre reinforced polymers (GFRP) and carbon fibre reinforced polymers (CFRP) composites; iv) wood agglomerates, carbon-carbon composites and graphite.


Fernandes, António; Costa, Florinda; Silva, Rui; Oliveira, Filipe; Amaral, Margarida; Cabanillas, Manuel

Our Inventors


Universidade de Aveiro
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