Differences between Cermet and Carbide

1. What is carbide?

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Cemented carbide is a powdery metallurgical material: a composite of tungsten carbide (WC) particles and a binder rich in metallic cobalt (Co). Cemented carbides for metal cutting applications consist of more than 80% of hard-phase WC. Other important components are additional cubic carbonitrides, especially in gradient-sintered grades. The cemented carbide body is formed, either through powder pressing or injection molding techniques, into a body, which is then sintered to full density. Carbides exhibit excellent properties such as high hardness, wear resistance, good strength and toughness, heat resistance, and corrosion resistance. Particularly noteworthy are their high hardness and wear resistance, which remain largely unchanged even at temperatures as high as 500°C and maintain significant hardness at 1000°C.

Carbides are widely used as cutting tool materials, including turning tools, milling cutters, planers, drill bits, boring tools, etc. They are employed for machining a variety of materials, including cast iron, non-ferrous metals, plastics, synthetic fibers, graphite, glass, stone, and common steel. Additionally, carbides can be utilized for cutting challenging materials like heat-resistant steel, stainless steel, high manganese steel, and tool steel.

2. What is cermet?

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Cermet is a composite material composed of ceramic and metal. It is defined by the ASTM (American Society for Testing and Materials) committee as a heterogeneous composite material consisting of metal or alloy and one or more ceramic phases, where the latter typically constitutes 15% to 85% by volume. Importantly, at the preparation temperature, there is minimal solubility between the metal and ceramic phases. In a narrow sense, cermet refer to a category of materials within composite materials where both metal and ceramic phases have interfaces in three-dimensional space.

Composition of cermet

Cermet are created by adding metal powder to the clay used in ceramic production, allowing the ceramic to withstand high temperatures without becoming easily breakable. Metal matrix cermet, also known as dispersion-strengthened materials, are produced by adding oxide fine powders to a metal matrix. Examples include sintered alumina (aluminum-alumina), sintered beryllium (beryllium-beryllium oxide), TD nickel (nickel-thorium oxide), and others. These are composite materials composed of one or more ceramic phases and metal or alloy phases.

In a broader sense, cermet also encompass refractory compound alloys, carbides, and metal-bonded diamond tool materials. The ceramic phase in cermet consists of oxides or refractory compounds with high melting points and high hardness, while the metal phase primarily consists of transition elements (iron, cobalt, nickel, chromium, tungsten, molybdenum, etc.) and their alloys.

3. Differences between Cermet and Carbide

Cutting performance

Cermet inserts offer higher precision and smoother cutting surfaces than WC carbide inserts. With cermet inserts, high precision machining is usually achieved in a single cut. Tungsten carbide inserts perform better in softer materials and often cut faster.

Cutting life

Cermet inserts have better wear resistance and therefore longer life, while WC tungsten carbide inserts are generally better suited for mass production machining of workpieces.

Machining performance

Cermet inserts are relatively brittle and are prone to breakage under impact. In contrast, WC (tungsten carbide) carbide inserts are simple to manufacture and easy to use and maintain.

4. Conclusion

Compared to cemented carbide, cermet has improved wear resistance and reduced smearing tendencies. On the other hand, it also has lower compressive strength and inferior thermal shock resistance. In conclusion, WC (tungsten carbide) carbide inserts and cermet inserts each have their own advantages and disadvantages. Choosing the appropriate inserts depends on the workpiece and processing characteristics, considering factors such as cost-effectiveness, machining lifespan, and overall effectiveness.

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