## 3 Results and Discussion
### Results of Industrial Tests

Table 8: Rate of wear of saws 2, 4 and 6 as a function of sawing time at the sawmill. Taking all wear indexes into account (recession on the rake and clearance faces and the width of the wear land), the percentages of decrease in wear rate when using the coated and edge-modified saw are presented in Table 9. As seen, the above-mentioned saw significantly decreased wear rate compared to other saws especially in the second leg of the test (between 480 and 960 min). The results revealed the value of edge modification combined with the deposition of a CrN/CrCN coating in improving the wear resistance of circular saws used in primary wood processing. The wear rate of the edge-modified saws was lower compared to the up-sharp saw. For the former, the size of the edge preparation on the rake face (20 \(\upmu\)m) is large enough to withstand the shock of interrupted cutting. Furthermore, the smaller edge preparation (10 \(\upmu\)m) on the clearance face prevents the saws from rubbing the workpiece, reducing frictional heat. On top of that, the variable configuration of edge preparation provided by cutting edge modification reduces the ploughing action and frictional heat during cutting. In variable edge modification, the edge radius changes along the corner of the tips. Therefore, the ratio of the uncut chip thickness to edge radius remains constant. In this case, the cutting edge should experience a lower temperature gradient. [PERSON] et al. [48] stated that variable edge microgeometry can potentially reduce heat build-up during the turning of a titanium alloy. In the present study, the edge preparation evenly tapered from the full size (20 \(\upmu\)m) on the primary cutting edge to 4 \(\upmu\)m on the flank side edges. The latter mainly remained sharp to cut the spring back wood and reduced the frictional heat developed from side rubbing. This led to a lower wear rate of the edge-modified saws compared to the up-sharp one. In addition, the combination of cutting edge modification and coating treatment significantly decreased the wear rate, as seen in Figure 21 and Table 9. CrN/CrCN multilayer coating was efficient in reducing frictional heat on the rake and clearance faces as well as sides of the carbide tips. Its high adhesion and low coefficient of friction assisted in significantly increasing wear resistance. As highlighted by [PERSON] et al. [49], high adhesion and low COF of coatings play a crucial role in the performance of wood cutting tools by reducing the cutting forces and increasing the stability of the cutting process. Typical results ensuing from SEM characterization of the rake face of tips taken from each saw are presented in Figure 22a,b,d,e. The latter show the absence of crumbling, delamination, or cracks in the coating after 480 and 960 min of sawing. The saws without coating (#6) show evidence of cobalt binder removal, transgranular cracks in the WC grains, and grain pull out on the rake face (Figure 22c,f). As stated by [PERSON] et al. [50] and [PERSON] et al. [51], the synergetic interaction between mechanical wear and heat generation, particularly frictional heat, is the main cause for partial extrusion of the cobalt binder, followed by carbide grain removal. These results highlight the importance of depositing multilayer coating on the saw tips in primary wood processing.