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The tribological response of multilayer micro/nanocrystalline diamond coatings grown by the hot filament CVD technique is investigated. These multigrade systems were tailored to comprise a starting microcrystalline diamond (MCD) layer with high adhesion to a silicon nitride (Si3N4) ceramic substrate, and a top nanocrystalline diamond (NCD) layer with reduced surface roughness. Tribological tests were carried out with a reciprocating sliding configuration without lubrication. Such composite coatings exhibit a superior critical load before delamination (130 -200 N), when compared to the mono-(60-100 N) and bilayer coatings (110 N), considering ∼10 mm thick films. Regarding the friction behaviour, a short-lived initial high friction coefficient was followed by low friction regimes (friction coefficients between 0.02 and 0.09) as a result of the polished surfaces tailored by the tribological solicitation. Very mild to mild wear regimes (wear coefficient values between 4.1 10 −8 and 7.7 10 −7 mm 3 N −1 m −1 ) governed the wear performance of the self-mated multilayer coatings when subjected to highload short-term tests (60-200 N; 2 h; 86 m) and medium-load endurance tests (60 N; 16 h; 691 m).

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