resumo
The present work is a comparative study of different combinations of microcrystalline (MCD) and nanocrystalline diamond (NCD) varieties (monolayers, bi-, tri- and fourfold layers) grown by hot filament CVD technique on silicon nitride ceramic substrates. The Hertzian stress states under static indentation are estimated and compared on the basis of the von Mises stress parameter. The diamond multilayer morphology and the structural quality were evaluated step-by-step by SEM, AFM and UV-Raman spectroscopy. By using the multilayer strategy, starting with a MCD adherent layer on Si3N4 ceramic substrates and finishing with a NCD smooth layer at the top, it was possible to keep the surface roughness at a lower RMS level, of around 90 nm. The fourfold multilayer configuration allowed obtaining 10 mu m thick diamond coatings that endure an indentation load of 800 N with a Brale cone, before film spalling-off. This behaviour is determined by the high bonding strength of the initial MCD layer grown on the Si3N4 ceramic substrate, where the von Mises stress (J(2)(1/2)) is estimated as 27 GPa. (C) 2013 Elsevier B.V. All rights reserved.
palavras-chave
CHEMICAL-VAPOR-DEPOSITION; SILICON-NITRIDE CERAMICS; ADHESION STRENGTH; CUTTING TOOLS; THIN-FILMS; COATINGS; NANOCRYSTALLINE; NANO; SI3N4; WATER
categoria
Materials Science; Physics
autores
Salgueiredo, E; Amaral, M; Almeida, FA; Fernandes, AJS; Oliveira, FJ; Silva, RF
nossos autores
Filipe José Alves de Oliveira
Investigador Principal
Flávia Aparecida de Almeida
Bolseiro de pós-Doutoramento
Rui Ramos Ferreira e Silva
Professor associadoagradecimentos
This work was conducted under the frame of the FCT project MULTIDIACOAT-PTDC/EME-TME/100689/2008. E. Salgueiredo, M. Amaral and F.A. Almeida gratefully acknowledge FCT for the grants SFRH/BD/41757/2007, SFRH/BPD/26787/2006 and SFRH/BPD/34869/2007, respectively.