Influence of CrxNy coatings deposited by magnetron sputtering on tool service life in wood processing

Cubic CrN(200) and a mixture of 25% CrN + 75% Cr2N(111) coatings were depos ited by magnetron sputtering onto carbide tools and tested in wood machinin g. The composition of the layers was determined by X-ray photoelectron spec troscopy (XPS) analyses. Scanning electron microscopy (SEM) observations sh owed that Cr2N layers have a columnar structure while CrN layers seem to be featureless. Secondary ion mass spectroscopy (SIMS) profiles have shown a good homogeneity of the layers and no interdiffusion of the different speci es into the substrate. The mechanical properties of the chromium nitride co atings were characterized by residual stress measurement, hardness measurem ents and scratch adhesion tests. The layers have some compressive stresses in the range -1.7/-2.1 GPa and -0.4/-1 GPa for CrN and Cr2N, respectively. The more adherent layers are CrN ones which exhibit hardness up to 1900-210 0 HV. Cr2N layers are harder (up to 1900-2100 HV) but less adherent. Machin ing tests were performed up to 5 and 10 km of cutting distance with industr ial routers on Oriented Strand Board. Tool wear and service life were compa red between the uncoated and coated tools. First, it has been observed that the edge wear is very high, just at the beginning of the routing process. The best result was shown by a carbide tool CrN coated on both faces; the s ervice life of this tool is four times higher than the one of an uncoated t ool. (C) 2001 Elsevier Science B.V. All rights reserved.