Adhesion behaviour assessment on diamond coated silicon nitride by acoustic emission


Acoustic emission (AE) from cracking events in microwave plasma assisted chemical vapour deposition diamond coated Si3N4 ceramics during Brale indentation tests was investigated. The experiments were conducted in a modified macro-indentation technique, that avoids the discrete loading limitation of conventional indentation by using a constant indenter displacement rate. The recorded AE signals, in conjunction with scanning electron microscope post-observations of the cracking pattern, allowed the adhesion behaviour investigation of the diamond film/ceramic system. The AE graphs evidenced that the most intensive acoustic peaks arise when film spalling takes place. The Si3N4 surface roughness was used as a variable to confirm the feasibility of the method. A better adhesion performance was achieved for the substrate with a higher roughness. For the diamond coated as ground substrate the critical load for film detachment is similar to 1000 N, while the film adhesion on the coated polished material is weaker. The assessment of the interfacial cracking resistance of the films gives a maximum value of 1372 kN m(-1). (C) 2002 Elsevier Science B.V. All rights reserved.




Materials Science


Belmonte, M; Fernandes, AJS; Costa, FM; Oliveira, FJ; Silva, RF

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