Tribological properties of NCD coated cemented carbides in contact with wood

Cemented carbides coated with diamond layers are promising materials for mills in the wood industry. Therefore, a study of the tribological properties of the contact between this material and wood is interesting and important. Wood is a specific material with a highly anisotropic structure, which causes roughness of its surface. For example, the friction coefficient (mu) of wood in contact with polished steel coated with a smooth DLC layer, has a relatively high value of mu = 0.2-0.5. Cemented carbides, as manufactured for tools for wood milling purposes with roughness R-z = 0.66 mum, have been modified with a nanocrystalline diamond film (NCD) using the RF PACVD method. The surface of the NCD coating showed 'sharp hills' morphology, but the surface roughness of cemented carbide decreased slightly after coating. The friction was very high (mu = 0.7-0.8 at v = 1 m/s; F-N = 60 N) and it depended on the species of wood. When examining oak and poplar using carbides coated with the thickest NCD layer and a DLC film on top, this value decreased by 30% with respect to that of uncoated carbides. For fibreboard against NCD, the value was increased. Comparing the friction of NCD against wood to its friction against steel, titanium and aluminium alloys, we could see that the roughness of wood was the main factor which determined its tribological behaviour. Prime novelty the tribological properties of a NCD layer deposited on cemented carbides with wood. (C) 2001 Elsevier Science B.V. All rights reserved.