Since the development of powder metallurgy technology, considerable progress has been made. The hardness of the products obtained through this technology is even not far from that of diamond, the hardest material in the world.
From powder to carbide insert? This sounds incredible, but one of the hardest materials in the world is made of powder. Hold back your curiosity, and then uncover the mystery of the cemented carbide insert production process for you.
Tungsten oxide is mixed with carbon and processed into tungsten carbide in a special furnace, which is the main raw material for all cemented carbides. Tungsten carbide is an extremely hard and fragile material that is used as the main component of cemented carbide. Tungsten carbide is mixed with cobalt, which is crucial to the properties of cemented carbide. The more cobalt, the better the toughness of the cemented carbide; on the contrary, the harder and more wear-resistant. The weight ratio of different components is carried out with the highest precision. The error of a batch of 420 kg of raw materials cannot be greater than 20 grams. Mixing is a precision metallurgical operation. Finally, the mixture is ground into a fine and delicate powder in a large ball mill. The mixture must be spray dried to obtain the correct fluidity. After grinding, the particle size of the powder reaches 0.5-2.0 um.
First, press with punches and dies in a highly automated CNC controlled press to obtain the basic shape and size. After pressing, the blade looks very similar to a real carbide blade, but the hardness is far from reaching the standard. The robot transfers the pressing blade to a disc made of heat-resistant material.
For hardening, the blade is heat treated at 1500 degrees Celsius for 15 hours. Through the sintering process, the molten cobalt and tungsten carbide particles are bonded together. The sintering furnace treatment process does two things: the blade shrinks significantly, and the shrinkage must be accurate to obtain the correct tolerance; secondly, the powder mixture is transformed into a new metallic material, which becomes a cemented carbide. Now, the blade has reached the expected hardness, but it has not reached the point where it can be delivered. Before proceeding to the next step of production, we will carefully check the size of the blade in the coordinate measuring machine.
Only through diamond grinding can the carbide blade have an accurate shape. The blade is subjected to various grinding processes according to the geometric angle requirements. Most grinders have built-in measurement controls to inspect and measure the blade in several stages.
The cutting edge is processed to obtain the correct shape to achieve the maximum wear resistance required for machining. These blades can be brushed with a special brush with a silicon carbide coating, and the final result must be checked regardless of the processing method. 90%-95% of all blades have some kind of coating. Ensure that there are no foreign particles on the surface of the blade to prevent such particles from adhering under the coating, thereby affecting the performance of the tool.
Chemical vapor deposition (CVD) and physical vapor deposition (PVD) are two existing coating methods, and the choice of method depends on the material and processing method. The thickness of the coating depends on the blade application, and the coating determines the durability and life of the blade. The technical trick is that the surface of the cemented carbide is coated with many very 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, put the blade in the furnace, and add chloride and oxide in gas form 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 to make the blade A homogeneous coating that is only a few thousandths of a millimeter thick is obtained. Some coated blades get a golden surface and become more valuable, and their durability is 5 times higher than that of uncoated blades. In PVD, the blade is sprayed at 400 degrees Celsius.
The blade passes the automated inspection, and then we will laser mark the material on the blade, and finally pack it. The blade box is marked with product information, serial number and date, which is a promise to ensure that users receive excellent quality and service.
After the packaging is complete, the blades can be distributed to customers.
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