# Surface Engineering of Woodworking Tools, a Review
## 5 Coatings Used for Woodworking Tools
### Binary Coatings Doped with Various Elements  
New requirements for tools, related to the increase in machining parameters or type of machining and the processing of new materials, led to the design and manufacture of new coatings. Two directions of change in coatings for woodworking tools were observed: formation of three- and more-component coatings, and forming of multilayer coatings. The influence of such elements as C, Si, Al, B, W, and Zr on the properties of coatings based on titanium [26; 29; 41; 64; 65] and chromium [38; 41; 66; 67] was investigated. The next group, multilayer coatings, was also intensively studied [39; 41; 68; 69; 70; 71; 72; 73]. Investigations of multilayered structures with chromium nitride as one of the layers indicated that it was possible to further improve hardness and toughness [14; 74; 75]. Some information about the applied coatings, the effects of their use, and the materials machined are summarized in Tables 13-13. The coatings deposited on the tools are manufactured generally using PVD and CVD methods. Here, the results of PVD coatings are analyzed and summarized in Table 13 (magnetron sputtering) and Table 14 (cathodic arc evaporation). In Table 13, are gathered coatings formed and described by authors as Physical Vapor Deposition (PVD). It should be noted that the first works including the assessment of the durability of the coating-modified tools did not reveal positive test results [76; 77]. Titanium nitride (TiN), titanium carbide (TiC), and titanium aluminium oxynitride (TiAlON) were formed by plasma-assisted chemical vapor deposition on tungsten carbide tools applied to milling laminated particleboard. It was found that the tools with TiC provided only a slight improvement, and the tools with TiN and TiAlON did not provide any improvement in wear resistance compared to the uncoated carbide tools [77]. The analysis of the results of tests of TiN, TiAlN and TiN/TiCN coatings deposited by the PVD method on K grade tungsten carbide tools used for continuous milling of particleboards showed that wear resistance depends on the quality of the substrate, with the grain size and binder (cobalt) content being the decisive factors in the tool. For tools with a low cobalt content and small grains, there was a slight improvement in wear resistance, while coatings deposited on tools with a higher cobalt content and larger grains reduced the wear resistance. The authors observed the chipping of the coatings on the tool rake face, which was related with poor adhesion of the coating to the substrate (tool), and indicated this as the primary cause of poor wear resistance. [78]. Also, [PERSON] et al. [68] indicated the poor adhesion of the coatings as the reason for its low wear resistance. For all tested systems: tool TiN, CrN, CrC, TiCN, and TiAlN, coating at both low and high cutting speeds of the wood-chip cement board, delamination occurred, as well as oxidation of the coating accelerated by the increase in cutting temperature. The above studies show the importance of adhesion to their wear resistance. The research indicates that the most important factors determining the improvement of the performance of woodworking tools, but also of other types of processing, are good adhesion of the coating to the substrate (tool), low friction coefficient, and good abrasion resistance [26]. Many research centers have been involved in the optimization of these factors, and the results of their work can be found in many reputable journals. The final results of these works, with reference to specific applications for woodworking tools, are also included in this study. [PERSON] et al. [38] investigated CrN-based coatings with the addition of Al or Si, because such three-component coatings have modified structural, mechanical and tribological properties, including higher resistance to oxidation, higher hardness, and lower friction coefficient. Medium density fiberboard was subjected to routing tests.