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powder

Tungsten oxide is mixed with carbon and processed in a special furnace to form tungsten carbide, the main raw material for all carbide. Tungsten carbide is an extremely hard yet brittle material used as the main component of cemented carbide. Tungsten carbide is mixed with cobalt, which is critical to the properties of the carbide. The more cobalt there is, the better the toughness of the cemented carbide; conversely, the harder and more wear-resistant it is. The weight proportioning of the different ingredients is carried out with the utmost precision. The error of a batch of 420 kilograms of raw materials cannot be greater than 20 grams. Mixing is a precision metallurgical operation, and finally, the mixture is ground into a fine and refined powder in a large ball mill. The mixture must be spray dried to obtain the correct flow properties. After grinding, the powder has a particle size of Ø 0.5-2.0 um.

suppress

First, the basic shape and size are obtained by pressing with punches and dies in a highly automated CNC-controlled stamping machine. After pressing, the blade looks very similar to a real carbide blade, but is nowhere near as hard as it should be.

sintering

To harden, the blades are heat treated at 1500 degrees Celsius for 15 hours. Through a sintering process, the molten cobalt is bonded to the tungsten carbide particles. The sintering furnace process does two things: the insert shrinks significantly, and the shrinkage must be precise to get the correct tolerances; and second, the powder mixture is transformed into a new material with metallic properties, called cemented carbide. The blade is now as hard as expected, but not ready for delivery. Before proceeding to the next production step, the dimensions of the inserts are carefully checked in a coordinate measuring machine.

grinding

Only through diamond grinding can carbide inserts be given an accurate shape. The blade undergoes various grinding processes according to geometric angle requirements. Most grinders have built-in measurement controls that check and measure the blade in several stages.

Edge treatment

The cutting edges are treated to obtain the correct shape for maximum wear resistance for the required machining. These blades can be brushed with a special brush with a silicon carbide coating, and regardless of the processing method used, the final result must be checked. 90%-95% of all blades have some kind of coating, make sure there are no foreign particles on the surface of the blade, prevent these particles from adhering under the coating and affecting the performance of the knife.

coating

Chemical vapor deposition (CVD) and physical vapor deposition (PVD) are two existing coating methods, and the method chosen depends on the material and processing method. Coating thickness depends on the blade application, and the coating determines the blade’s durability and blade life. The technical know-how is that the surface of the cemented carbide is coated with many extremely thin coatings, such as titanium carbide, aluminum oxide and titanium nitride, which can greatly increase the service life and durability.

If the CVD method is used for coating, the blade is placed in a furnace, and chlorides and oxides in gaseous form are added together with methane and hydrogen. When the temperature reaches 1000 degrees Celsius, these gases interact and also act on the surface of the cemented carbide, making the blade A homogeneous coating is obtained that is only a few thousandths of a millimeter thick. Some coated blades gain a golden surface, become more valuable, and are up to five times more durable than uncoated blades. PVD sprays the blade at 400 degrees Celsius.

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