Technical background of cemented carbide

2021-03-18

Cemented carbide is based on refractory metal hard compound, metal as binder, high hardness, good red hardness, high chemical stability, high compressive strength, high wear resistance material sintered through powder metallurgy process , Known as the "Industrial Teeth". The cutting speed of cemented carbide tools is about 4~7 times that of high-speed steel tools, and the working conditions are more severe during the cutting process, and they are prone to severe wear under frequent and frequent impacts, thermal alternating loads, alternating bending stresses, and high temperatures. Under the action of factors such as cutting edge wear, chipping, thermal deformation, fatigue, fracture and other failure forms. At this stage, the performance of cemented carbide is mainly improved through the development of new cemented carbide materials and cemented carbide surface strengthening technology. However, there are still problems such as complex equipment, high preparation costs, and high technical difficulties, which limit my country's cemented carbide The quality of alloy products has been further improved. In recent years, with the continuous improvement of the processing level of the manufacturing industry, the demand for high-quality cemented carbide is increasing. At the same time, the use of cemented carbide in the mold industry is also increasing day by day.

Since the toughness of cemented carbide mainly depends on the cemented phase, and the cemented phase of WC-Co cemented carbide has allotropic transformation and solid solution composition changes with temperature changes, which provides for the heat treatment of WC-Co cemented carbide possibility. Quenching can inhibit the precipitation of WC and the allotropic transformation of Co. Therefore, the heat treatment of WC-Co cemented carbide can improve its flexural strength to varying degrees. However, considering that the commonly used cemented carbide in engineering generally contains less cobalt, therefore, the strengthening effect of heat treatment on the alloy is small.

With the continuous advancement of "Made in China 2025", the high-end equipment manufacturing industry's requirements for materials continue to increase. After traditional heat treatment, the material still has some shortcomings, such as unstable structure after quenching, higher thermal stress and structural stress, uneven structure, etc., which will deteriorate the material performance and affect the service life of the material. Generally speaking, it is difficult to solve such problems through a single heat treatment process. As an important additional process of heat treatment, cryogenic treatment can effectively optimize the performance of materials after heat treatment, and has a significant effect on extending the service life of materials. Cold treatment has been widely used in high-end manufacturing, precision instruments and aerospace industries.

Cryogenic treatment of cemented carbide was first seen in the Japanese publication "Mechanical Technology" in 1981, which reported that after cryogenic treatment of cemented carbide knives and molds, the wear resistance and crush resistance were significantly improved compared with ordinary low-temperature treatment. With the increasing application of cemented carbide materials in industry, its cryogenic modification technology has attracted the attention of scholars at home and abroad. At present, a large number of studies have shown that cryogenic treatment can improve the wear resistance, strength, toughness and other comprehensive properties of cemented carbide, and extend the service life of cemented carbide tools and molds. However, the traditional cryogenic treatment of cemented carbide is mainly for finished tool products, and its implementation process is independent of the heat treatment of cemented carbide. Therefore, in order to adjust the structure of the cemented carbide to a greater extent and significantly improve the performance of the cemented carbide, the cryogenic treatment and the heat treatment of the cemented carbide are organically matched, and the metastable state in the structure is promoted through the adjustment of process parameters. The transformation and stabilization of the binder phase will promote the precipitation of more η phases in the structure, thereby maximizing the strength and toughness of the cemented carbide.