Influence of knife-surfaces modification with hard coatings on the peelingwood process

The explanation of the needs and inputs for extending the service life of t ools when the quality of the surface, lower energy consumption and the time saved are taken into consideration are comprehensible. One of the methods, recently taking over the market for tools for metals processing, is to cov er the cutting edges with hard anti-abrasive coatings such as TiN, Ti(C,N), ZrN, (Ti, Zr)N, TiAlN. Those coatings ameliorate the service life of tools many times [T. Burakowski, T. Wierzchon, Surface Engineering for Metals, W NT, Warszawa, Poland, 1995, p. 554; R. Hatschek American Machinists, March 1983; M.E. Sjostrand, A.G. Thelin, Proc. 8th Internat. Conf. Vacuum Metallu rgy, Lint, Austria, Einsenhutte Osterreich, 1985; W.D. Sproul, R. Rothstein , Thin solid Films 126 (1985) 257]. That is why attempts to apply them, to wood and wood-based products processing are being carried [P. Beer et al., Proc. 13th Internat. Wood Machining Seminar, UBC, Vancouver, Canada, 1997, pp. 699-707; C. Kato et al., Mokuzai Gakkaishi (J. Japan Wood Res. sec.) 36 (8/10) (1990) 615-623, 844-850; C. Kato et al., Proc. 12th Internat. Wood Machining Seminar, Kyoto, Japan, 1995, pp. 314-323; J. Sheikh-Ahmad et al., Proc. 12th Internat. Wood Machining Seminar, Kyoto, Japan, 1995, pp, 282-2 91]. The aim of the present study was to examine whether the peeling proces s can be improved by modifying the surface of the cutting tools. The modification of the clearance and rake surfaces of the tools consisted of covering them with TiN, (Ti,Zr)N and CrN anti-abrasive coatings and with a chromium layer. The present experiments have shown that the well-adherent anti-abrasive coa tings increase the service life of the cutting tools. However, the remainin g parts of the coating, which rest on the knife edge, reduce the quality of the surface of the. veneer cut from the specimen. The modification of kniv es made of low-ahoy steel with an edge angle of 20 degrees with hard coatin gs, which are usually used for peeling, seems still to be unsuitable for in dustrial application. Better results at this time could be achieved by a de ep study of knife-edge forms and by improving the durability of the knives by means of low temperature Ton Nitriding. (C) 1999 Elsevier Science S.A. A ll rights reserved.