## 3 Results and Discussion
### Results of Industrial Tests
Different wear mechanisms on the cutting edges of all saws after 960 min of sawing are presented in Figure 25. The wear mechanisms are identical to those observed for the same types of tips after 480 min (Figure 24). Chipping was the principal wear mechanism responsible for the degradation of the cutting edges of saw #4 having up-sharp tips (Figure 25b,e). On the contrary, saws #2 and #6 with edge modification showed micro chippings and few chippings on their cutting edges, but to a much lesser extent than what was observed of saw #4, as shown in Figure 25a,c,d,f. Thus, variable engineered micro-geometry significantly reduced the tendency of the carbide tips to chip after 960 min of woodworking. Figure 24: Typical aspect of the cutting edge of tips (rake face view): (**a**,**d**) saws #2, (**b**,**e**) saws #4, and (**c**,**f**) saws #6 after 480 min of sawing. To precisely investigate the failures on the cutting edge, SEM micrographs of the worn cutting edge (from the rake face view) acquired at higher magnification are presented in Figure 26. The coated saw with up-sharp tips sustained transgranular crack in most WC grains after 480 and 960 min of sawing (Figure 26b,e). Apart from the crack in the cobalt binder, most WC grains lacked interconnecting cobalt. Furthermore, grain crushing, debonding, and removal of many WC grains occurred due to the continuous shock of intermittent cutting (Figure 26e). [PERSON] [43] pointed out that during wood machining, fluctuating cutting forces coupled with frictional heat generated on the rake and clearance faces causes oscillation of WC grains leading to cobalt extrusion followed by grains falling out from the matrix. Figure 26: SEM micrographs of the defects on the cutting edges (rake face view): (**a–c**) saws #2, 4, and 6, respectively after 480 min of sawing and (**d–f**) saws #2, 4, and 6, respectively after 960 min of sawing. Figure 25: Typical aspect of the cutting edge of tips (rake face view): (**a,d**) saws #2, (**b,e**) saws #4, and (**c,f**) saws #6 after 960 min of sawing. According to [PERSON] et al. [55], as the cutting edge is worn, the edge radius increases, causing the rake and clearance angles to decrease. This condition increases the ploughing action, creating frictional heat and inducing larger cutting forces on the cutting edge [56], thus leading to rapid tool wear [57]. However, there were a few cracks in the binder phase, reduced binder extrusion, and fewer transgranular cracks in WC grains for the saws having edge modification (Figure 26a,c,d,f). Most regions on the modified cutting edges remained intact. The reason is explained by the strengthening of the cutting edge, particularly at its corners. The variable configuration of edge preparation made the edge keener and reduced the ploughing area in front of the tool tip [58], thus minimizing edge degradation. Typical SEM micrographs (from the clearance face view) of the corners of all saws used during 480 and 960 min of sawing are shown in Figure 23.0 Apart from breakage (Figure 27b), some of the tips of the coated saw with up-sharp cutting edge geometry suffered from abrasion wear (Figure 27e). The latter is due to the degradation of cutting edges, leading to larger contact length between the clearance faces and the wood. As a result, the level of frictional heat was concentrated in this area. Moreover, frictional heat developed from side rubbing on the spring back layer of the wood is another source of heat affecting the abrasion wear mechanism. As seen in Figure 27e, the coating was partially delaminated from the abraded area. No breakage or chipping was observed at the corners of edge-modified tips as a result of corner strengthening by the honing process (Figure 27a,d,c,f). Abrasion took place on a small area at the corner of the tips of the uncoated saw that had undergone edge modification, as presented in Figure 27f. The corners of the tips of the coated saw with edge modification remained intact and no breakage and abrasion wear took place (Figure 27a,d).