Cr2N/CrN multilayer coatings for wood machining tools

Results from a recent research project aimed at forming a wear-resistant coating based on chromium on tools for wood machining are presented. Cr2N/CrN multilayer coatings deposited on HS6-5-2 steel substrates using cathodic arc evaporation were tested. These coatings were formed from 7 bilayers about 340 nm thick and equally thick Cr2N and CrN layers. Cr2N and CrN monolayer coatings were also prepared. Hardness measurements, indentation and scratch tests, friction and wear were performed to characterise the mechanical properties. The wear tracks and Rockwell indentations enable wear mechanisms of the coatings to be assessed. The results of the Cr2N/CrN coatings showed high hardness (about 22 GPa) and a critical force > 95 N and a low wear rate. Industrial tests of planer knives with Cr2N/CrN multilayer coatings were carried out on a down-spindle milling machine to determine the durability of tools with wear-resistant coatings for woodworking. These tools showed a twofold increase of life time. Another positive feature of the use of such tools was the increase of the quality of wood surface machined compared with use of uncoated tools.