Quality coating allows saw blade to stay sharp much longer and consume less power. There are two different categories of coatings that can be used on circular saw blades, one for the plate and the other for the teeth. When a blade has both categories of coatings, they will be different coatings, because they accomplish different purposes.
Friction
The blade plate may be coated as a protection against rusting and/or friction. Modern metalworking has developed variety of manufacturing methods, and uses different alloys in the process of casting in order to improve durability. The coating type depends on the hardness of a metal of which saw blade is made; hook and clearance angles, tooth design, material sticking and general purpose. Some manufacturers paint the blade plate, mostly in blue, red or orange, to provide brand identification. If this is done, it still provides rust protection to the plate. There are a few high cost blades which are coated with Teflon (PTFE), in order to reduce friction. This type of coating can be very valuable, as the greatest amount of friction comes from debris captured between the blade plate and the material being cut. By coating the blade plate, this debris won’t stick to the blade, causing it to be more easily ejected from the kerf. Additionally, there may be times where the material pinches the blade, even though the plate is thinner than the teeth. This type of problem is especially prevalent with hand-held circular saws and power miter saws.
Coating Teeth
Coating of the teeth is an important part of prolonging a blade’s life. Wood products are highly fibrous, which tends to dull any blade. When cutting hard materials like composite decking or plywood, the temperature easily approaches the melting point. This brings the need for overheating protection as an addition. The harder the material used on the teeth, the longer the blade will last without resharpening. For this reason, a number of extremely hard materials are used to coat the teeth.
The blade teeth can either be part of the same high speed steel as the blade plate or welded on teeth of a harder material. In the case of high speed steel blades (HSS), the teeth may be electroplated with a harder material to increase blade life. While high speed steel blades are the least expensive blades available, they also have the shortest usage life before coming dull. However, high speed steel blades are easily sharpened. If the blade had coated teeth, sharpening removes this coating.
Carbide Coatings
Because of the short life of high speed steel blades, most circular saw blades used by professionals and serious hobbyists are “carbide tipped”. Common C3 carbide offers better heat and wears resistance, and can be resharpened several times. C4 carbide saw blades have much better properties in general, but also the price that accompanies it. The mark ‘C’ stands for durability grade. The actual teeth of the blade are usually made of tungsten carbide, which is brazed to the blade plate. These are labeled as TCT circular saw blades (Tungsten Carbide Tipped). Tungsten or wolfram (W) is a metal with high melting point, density and position on the Mohs scale of hardness. Tungsten Carbide, often referred to as just “carbide” is considerably harder than high speed steel. As such, the blade lasts longer, without resharpening. Special equipment and techniques are needed for sharpening carbide tipped blades. Tungsten-carbide tipped saw blades are generally considered as “Premium” grade blades.
Even the carbide teeth can be improved upon by coating. Wolfram, Titanium, Cobalt or Vanadium may be electroplated onto the carbide, increasing its surface hardness and reducing wear on the teeth. It allows them to stay sharp even longer. The material can be identified by the color of the blade. The process usually includes high pressure and temperature, under the influence of an inert gas or vacuum. Next to the permanent sharpness and simultaneously clean cut, such coatings have anti-corrosion properties so the rust can’t damage the inner structure of metal. The only drawback of carbide tipped saw blades is re-sharpening. As with the high speed steel blades, when resharpened, this coating is lost.