Advantages of depositing multilayer coatings for cutting wood-based products

An effective coating for cutting wood-based products, especially during interrupted cutting operations, must have excellent impact resistance, associated with excellent adhesion to the substrate, high hardness and corrosion resistance. At the beginning of the cutting operations, the impact has significant effects on the substrate, leading to variable material loss at the cutting edge. In order to improve the impact resistance of coated tools an optimized long period-multilayer coating was deposited on a cemented carbide substrate. These coatings are based on an alternate sequence of hard layers with softer monolayers, which work like a fuse in an electric circuit; when subjected to high impact stress crack propagation induces the delamination of hard layers, thereby avoiding the collapse of the entire coating, as in bulk laminated macrocomposites. From cutting tests of wood-based products, which used cutting tools coated with multilayer coatings based on Ti–W–N/Ti–W or Cr–W–N/Cr–W with different periods, the best result was achieved by the deposition of the multilayer coatings Cr–W–N/Cr–W (3 layers). This solution increases by 500% the ability to cut through wood-based products. In spite of this, the Ti–W–N (HV = 51 GPa; Lc2 > 80 N) has a slightly superior cutting performance to the Cr–W–N (HV = 43 GPa; Lc2 > 80 N). This study based on real cutting tests and applied using identical cutting parameters to those used in the industry, shows new solutions that can be implemented with success in the industries involved in cutting wood-based products.