CrxNy hard coatings deposited with PVD method on tools for wood machining

Although well known and widely used, tools modified with hard coatings are still not applied to the wood industry. Difficulties come from mechanical, physical and tribological properties of wood and of wood based materials together with particular parameters of their processing. The aim of this study was to synthesise hexagonal and cubic chromium nitride coatings and apply them in wood processing to improve cutting tools' wear resistance. The apparatus used was an industrial type router. The material subjected to cutting was OSB (Oriented Strand Board). The cutting tools with an edge angle of 55 degrees were cemented carbide inserts. The coatings were deposited by triode sputtering system; the hexagonal phase was obtained for 10% of nitrogen in the Ar + N-2 mixture used in the discharge, the cubic one was obtained for a percentage higher than 20%. The composition of coatings was determined by EDS and WDS microanalysis and SEM cross-section observations were performed. The mechanical properties of layers were determined by stress measurements and by a wear test performed with in situ method. It reveals that the most resistant coatings are the Cr2N films. These optimal conditions of deposition have been applied to cutting tools in routing process. It appears that CrN or Cr2N coatings deposited on both tools' faces ameliorate significantly tools wear resistance. (C) 2000 Elsevier Science B.V. All rights reserved.