Tungsten Carbide

High Hardness
Tungsten carbide is an extremely hard material, which is only surpassed by diamond. The hardness of tungsten carbide makes it an ideal material for cutting and machining tools. Hardness is an important property of tungsten carbide, which is tested by the Rockwell Hardness Tester. A pointed diamond indenter is forced into the tungsten carbide, and the depth of the hole is a measure of the hardness. In manufacturing tungsten carbide, many factors will affect the hardness, such as the amount of cobalt, the grain size, the amount of carbon, and the manufacturing process.

High Melting Point
Tungsten carbide has a melting point of approximately 5,700℃, which is significantly higher than the melting point of most other metals. This high melting point makes tungsten carbide ideal for use in high-temperature applications. The high melting point makes tungsten carbide cannot be manufactured by normal forging technology. Tungsten carbide products are manufactured by powder metallurgy, through mixing, milling, compacting, sintering, and checking.

Chemically Stable
Tungsten carbide is composed of tungsten and carbon atoms, which are both stable to oxygen and other elements. Tungsten carbide is highly resistant to chemical attack and does not corrode in most environments. This chemical inertness makes tungsten carbide an ideal material for use in chemical processing equipment and areas where corrosion resistance is required.

Low Coefficient Of Thermal Expansion
The mean coefficient of thermal expansion indicates the amount of expansion when the tungsten carbide is heated. The expansion of the tungsten carbide follows the expansion of the temperature. The more binder powder in the tungsten carbide, the higher the thermal expansion of the tungsten carbide will be. Tungsten carbide has a very low coefficient of thermal expansion, meaning that it expands very little when heated. This property makes tungsten carbide ideal for precision instruments and applications where dimensional stability is required.

Electrically Conductive
Despite being a refractory metal, tungsten carbide is electrically conductive due to the presence of carbon in its crystal structure. This electrical conductivity makes tungsten carbide ideal for electrical applications such as electrodes and contacts.

Tungsten carbide grades can be differentiated by chemical makeup, performance, and applicability. The several grades available domestically can be split into range grades: tungsten-cobalt (YG), tungsten-titanium-cobalt (YT), tungsten-titanium-tantalum (niobium)-cobalt (YW), and titanium carbide-based (YN). The grades vary in composition, toughness, heat resistance, and application.

Differences Between Various Tungsten Carbide Grades

1) Tungsten-Cobalt Alloys (YG)
Composition: Primarily composed of tungsten carbide (WC) and cobalt (Co), without titanium.
Performance Characteristics: Good toughness, high bending strength, and good thermal conductivity, but relatively low heat resistance (approximately 800–900°C). Higher cobalt content results in greater toughness and lower hardness.
Typical Grades: YG3, YG6, YG8 (the number represents the percentage of cobalt content, e.g., YG6 contains 6% cobalt).
Main Applications: Suitable for machining brittle materials such as cast iron, non-ferrous metals, and non-metallic materials. Also suitable for rough machining and applications with high impact loads. Fine-grained grades (such as YG6X) can be used for finish machining.

2) Tungsten-Titanium-Cobalt Alloys(YT)
Composition: Based on WC-Co, with the addition of titanium carbide (TiC). The TiC content is typically 5%–30%.
Performance Characteristics: Hardness, wear resistance, and heat resistance (up to 900–1000°C) are superior to YG alloys, but toughness, bending strength, and thermal conductivity are reduced, and grinding and welding become more difficult. Higher TiC content results in higher hardness and heat resistance, but also greater brittleness.
Typical Grades: YT5, YT15, YT30 (the number represents the percentage of TiC content).
Main Applications: Suitable for machining ductile materials such as steel, especially excelling in continuous cutting and high-temperature environments. YT5 (low TiC content) is used for rough machining, while YT15 or YT30 (high TiC content) is used for finish machining.

3) Tungsten-Titanium-Tantalum (Niobium)-Cobalt Alloys (YW)
Composition: Based on YT alloys, with the addition of tantalum carbide (TaC) or niobium carbide (NbC), which refines the grain structure and strengthens the grain boundaries.
Performance Characteristics: Excellent overall performance, possessing high hardness, high toughness, good wear resistance, and thermal stability. It is known as a "general-purpose cemented carbide."
Typical Grades: YW1, YW2 (the numbers are serial numbers and do not directly correspond to specific compositions).
Main Applications: Suitable for semi-finishing and finishing of various materials such as steel, cast iron, stainless steel, and heat-resistant alloys, especially suitable for processing mixed materials or applications requiring high stability.

4) Titanium Carbide-Based Materials (YN)
Composition: Primarily composed of titanium carbide (TiC) as the main hard phase, supplemented with small amounts of WC and NbC, and a binder, usually nickel (Ni) or molybdenum (Mo).
Performance Characteristics: Extremely high hardness and heat resistance (up to 92.5–93 HRA, heat resistance 1000–1300℃), approaching ceramic materials, but with poor toughness and high brittleness.
Typical Grades: YN05, YN10, YN01, YN15.
Main Applications: Suitable for high-precision finishing of steel parts, high-speed cutting, and applications requiring extremely high wear resistance, such as precision molds and semiconductor equipment parts.

Table 1: Typical Properties by Grade

Table 2: Other Tungsten Carbide Grades Data

Selection Recommendations:
For machining cast iron/brittle materials: Prioritize YG-type inserts (such as YG6, YG8) due to their good toughness and resistance to chipping.
For machining steel/ductile materials: Prioritize YT-type inserts (such as YT15 for finishing and YT5 for roughing).
For machining difficult-to-machine materials such as stainless steel and heat-resistant alloys, YW-type inserts (such as YW1, YW2) are recommended for their stable overall performance.
For high-precision, high-speed finishing, YN-type or fine-grained YG/YT grades (such as YG6X, YT30) can be used.

Note: Adding "X" after the grade designation indicates fine-grained material (e.g., YG6X), which improves hardness and surface quality; adding "C" indicates coarse-grained material, which enhances toughness.