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Technical Data
We are inspecting the safety and reliability such as hardness, strength, and fracture toughness, and trying the best to manufacture the superior products. Our porosity level is challenging the micro level and has meeted the high-precision inspection based on the CIS standard.
Both of Rockwell and Vickers are applied to indicate the hardness of cemented carbides, but generally Rockwell A (HRA) is used. In case of WC-Co cemented carbides, the hardness decreases as the Co content is increased. And in the same way, the hardness decreases as the WC grain size gets bigger. Furthermore, the hardness tends to decrease as the temperature gets higher.
Transverse Rupture Strength(TRS) is simple to inspect and is most common to be used to measure the strength of cemented carbides. This measurement is 3-points bending inspection based on CIS026. And it is shown in the diagram that TRS goes up as the Co content gets higher to approximately 15%, after this point it turns to go down.
Cemented carbides have the superior compression strength. The diagram is showing the relationship between Co contents and WC grain size. The compression strength reaches the maximum point of 6Gpa at 4 - 5 % of the Co content, and it goes down as Co content increases. In the same way, as the WC grain size gets bigger, the strength tends to decrease.
Toughness is showing the energy needed to fracture, and has been evaluated with Charpy impact test. However, the fracture toughness value called Stress Intensity Factor (Kic) is getting important. This inspection starts to make a crack on the sample and load it to fracture.
The energy required to get the propagation of the crack and fracture is applied as the fracture toughness (Kic). Fracture toughness can be used as a measure of the stickiness, and the crack propagates less as this value is bigger. As shown in the diagram, Kic is proportional to the Co content and WC grain size.
The energy required to get the propagation of the crack and fracture is applied as the fracture toughness (Kic). Fracture toughness can be used as a measure of the stickiness, and the crack propagates less as this value is bigger. As shown in the diagram, Kic is proportional to the Co content and WC grain size.
Cemented carbides have the excellent Young’s modulus which is 2 or 3 times as higher as that of steel. This is an important characteristic for structural materials. And the diagram is showing that this value goes down as Co content goes up.
The thermal expansion coefficient shall be considered in the environment of cemented carbides where the temperature changes. As the frequent examples, cemented carbides gets a crack when it is brazed with steel. This is because the thermal expansion coefficient is half or one-third as lower as that of steel. As shown in the diagram, the thermal expansion coefficient increases along with Co content.
