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

Abstract

The explanation of the needs and inputs for extending the service life of tools 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 cover 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, WNT, Warszawa, Poland, 1995, p. 554; R. Hatschek, American Machinists, March 1983; M.E. Sjostrand, A.G. Thelin, Proc. 8th Internat. Conf. Vacuum Metallurgy, Linz, 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. soc.) 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. 282–291]. The aim of the present study was to examine whether the peeling process 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 coatings increase the service life of the cutting tools. However, the remaining 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 knives made of low-alloy steel with an edge angle of 20° with hard coatings, which are usually used for peeling, seems still to be unsuitable for industrial application. Better results at this time could be achieved by a deep study of knife-edge forms and by improving the durability of the knives by means of low temperature Ion Nitriding.