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Reduced performance of circular saws due to premature chipping of their teeth has been a critical issue in woodcutting industry for many years. This research examined the impact of surface coating and variable engineered micro-geometry of the cutting edges of carbide teeth (tips) on the wear resistance of circular saws used in primary wood processing. CrN/CrCN/DLC, CrN/AlTiN, CrN/CrCN, and CrCN/TiSiCN were deposited on tungsten carbide-cobalt (WC-Co) substrates using the cathodic arc evaporation technique. The CrN/CrCN coating proved to be the one with highest wear resistance and adhesion among those studied. No sign of delamination was observed around the indentation of the CrN/CrCN coating after the adhesion test. Furthermore, no abrasion, delamination or crack was observed on the surface of the CrN/CrCN coating after the three-body abrasion wear test. The results of the dry-sliding wear test revealed that CrN/CrCN coating significantly decreased the wear rate of WC-Co substrates by 74%, 66% and 77% at sliding speeds of 50, 100 and 250 mm/s, respectively. Afterwards, a CrC/CrCN coating was deposited on the teeth of conventional circular saws. Next, the cutting edges of teeth were modified through variable engineered micro-geometry. Tests were conducted at a sawmill with three series of saws: 1-coated and edge-modified, 2-coated and conventional edge geometry, and 3-uncoated and edge-modified. Wood processing was performed during two shifts of 480 min each. The width of the wear land was the criterion used as the wear index. The results of industrial tests showed that saws with edge-modified teeth had significantly less chipping and no breakage at their corners compared to the saw without edge modification (conventional saw). After 480 min of sawing, the wear rate of the coated saw with edge modification decreased by 46% and 16%, compared to the coated saw without edge modification and the uncoated saw with edge-modified teeth, respectively. Those values reached 73 % and 41%, respectively, after 960 min of sawing. The study shows that by optimizing the surface chemistry and the geometry of the cutting edge of WC-Co tips, tool life can be significantly increased therefore reducing downtime due to saw replacement and resharpening, thus significantly increasing productivity in the first transformation of wood.

The effects of the Engineered Micro-Geometry (EMG) of the carbide teeth of circular saws on their wear rate and resulting sawing variation for 2-time intervals were studied. The objective was to improve the wear resistance of circular saws used during the primary transformation of wood. The tests were carried out under industrial production conditions with two series of circular saws; 1- with up-sharp tips, and 2- with cutting edges honed to adopt a waterfall geometry. The duration of the tests was 255 min and 645 min. Wood studs were sampled to measure sawing variation. Recession on the rake and clearance faces of the tips as well as the width of the wear land were measured. The wear mechanisms of the cutting edges of both types of saws were studied. Chipping and cracking were the two dominant wear mechanisms observed on the up-sharp tips. Saws with waterfall hone tips showed remarkably reduced chipping and cracking. Wear rate of the latter was notably lower than that of saws with up-sharp tips at both periods of sawing. Between-stud, within-stud, and total sawing variations decreased when saws with modified cutting edges were used.