# Detailed Classification of Cemented Carbides

As an indispensable “industrial tooth” in modern industry, cemented carbide—owing to its exceptional hardness, outstanding wear resistance, and superior thermal stability—plays a pivotal role in fields such as cutting machining, geological exploration, and aerospace. Its core microstructure is formed by refractory metal carbides (the hard phase) combined with a metallic binder (the binder phase) through powder metallurgy. Based on compositional and performance differences, cemented carbides can be systematically classified into four major categories: tungsten–cobalt (YG), tungsten–titanium–cobalt (YT), tungsten–titanium–tantalum (niobium) (YW), and titanium‑carbide‑based (YN). This article will, drawing on typical application scenarios, examine the technical characteristics of each type of cemented carbide and the rationale behind their selection.

### I. Tungsten-Cobalt (YG) Grades: An Effective Tool for Machining Brittle Materials

Tungsten–cobalt cemented carbides are primarily composed of tungsten carbide (WC) and cobalt (Co), with cobalt content typically ranging from 6% to 12%. They are characterized by high toughness, relatively low hardness (HRA 89–91.5), excellent thermal conductivity, yet moderate heat resistance. These properties make them an ideal choice for machining brittle materials:

1. **Cast Iron Machining**: In the rough machining of gray cast iron and ductile cast iron, the impact resistance of YG‑type carbide inserts effectively mitigates vibrations caused by intermittent cutting, thereby preventing chipping or breakage of the cutting edge. For example, YG8 (with 8% cobalt content) is commonly used for rough milling of automotive engine cylinder blocks; its flexural strength reaches 2,200 MPa, enabling it to withstand heavy‑load cutting conditions.

2. **Nonferrous Metal Processing**: When machining soft metals such as copper and aluminum, YG‑type carbides offer excellent thermal conductivity, enabling rapid heat dissipation and preventing thermal deformation of the workpiece. YG6X (with a fine-grained microstructure) can achieve a surface roughness as low as Ra 0.4 μm in the precision turning of copper components.

3. **Non-metallic Material Machining**: When machining hard and brittle materials such as glass and ceramics, the toughness of YG‑type alloys helps minimize chipping at the cutting edge, thereby extending tool life. For example, in milling quartz glass, the YG10X grade delivers a tool life that is ten times longer than that of high-speed steel.

### II. Tungsten-Titanium-Cobalt Grades (YT): The Heat-Resistant Pioneers for Continuous Machining of Steel Parts

By adding titanium carbide (TiC), the hardness of YT‑type alloys is increased to HRA 91–93, and their red hardness is significantly enhanced—retaining hardness even at 900–1000°C—though toughness is somewhat reduced. Their applications are primarily focused on continuous cutting of steel workpieces.

1. **General Steel Machining**: YT5 (with 5% TiC content) is suitable for rough turning of low-carbon steels, and its wear resistance effectively addresses the issue of built-up edge formation with long chips. In the turning of 45# steel, even at a feed rate of 0.3 mm/rev, the tool life remains consistently around 45 minutes.

2. **Machining of High-Hardness Steels**: YT15 (with 15% TiC) is used for finish turning of quenched and tempered steels, and its excellent oxidation resistance helps reduce crater wear. For example, in the finish machining of 40Cr steel, surface roughness can reach Ra 0.8 μm, with dimensional accuracy within ±0.01 mm.

3. **High-Speed Cutting Limitations**: Although YT‑type alloys exhibit excellent heat resistance, excessive cutting temperatures exceeding 1000°C can lead to chipping at the cutting edge; therefore, cutting speeds must be kept below approximately 120 m/min.

### III. Tungsten-Titanium-Tantalum (Niobium) Grades (YW): A Versatile Solution for Difficult-to-Machine Materials

By adding tantalum carbide (TaC) or niobium carbide (NbC), YW‑type alloys combine the toughness of YG with the heat resistance of YT, making them the preferred choice for machining difficult materials such as stainless steel and high-manganese steel.

1. **Stainless Steel Machining**: In the milling of 304 stainless steel, YW1 (with a TaC content of 3%) exhibits superior resistance to built-up edge compared to YT grades, resulting in a 30% increase in tool life. Its flexural strength reaches 1800 MPa, enabling it to withstand the impact of intermittent cutting operations.

2. **High-Temperature Alloy Machining**: YW2 (with 6% TaC) is used for turning Inconel 718 nickel-based alloy; its high-temperature hardness (HRA 85 at 800°C) effectively suppresses plastic deformation, while the surface roughness remains stable at Ra 1.6 μm.

3. **Composite Material Machining**: In the drilling of carbon fiber-reinforced polymers (CFRP), YW‑type alloys exhibit superior resistance to delamination, reducing interlaminar damage and yielding hole wall quality that outperforms conventional cutting tools.

### IV. Titanium Carbide-Based Grades (YN): The Ultimate Choice for Finishing and High-Speed Machining

Using titanium carbide (TiC) as the matrix and adding nickel (Ni) or molybdenum (Mo) as binders, YN‑type alloys achieve a hardness of HRA 93–95 and exhibit heat resistance comparable to ceramic materials, though they are relatively brittle. Typical applications include:

1. **Precision Finishing of Steel Parts**: YN10 (with 90% TiC content) enables mirror‑finish machining (Ra 0.2 μm) and achieves dimensional accuracy up to IT5 grade when used for precision turning of quenched steel.

2. **High-Speed Machining**: In high-speed milling of aluminum alloys (cutting speeds exceeding 2,000 m/min), the heat resistance of YN‑type alloys prevents tool softening, resulting in a material removal rate five times higher than that of YG‑type alloys.

3. **Special-Scenario Restrictions**: Due to their relatively high brittleness, YN‑type alloys should be protected from impact loads and are typically used in stable machining environments such as CNC machine tools.

### V. Core Logic of Classification and Selection

The selection of cemented carbide must comprehensively consider three key factors: material hardness, cutting temperature, and impact load.

1. **Brittle materials (such as cast iron):** Prefer YG grades to leverage their toughness in absorbing impact energy.

2. **Plastic materials (such as steel):** Select YT grades for ordinary steel or YW grades for stainless steel, depending on the material’s hardness.

3. **High-Speed/High-Temperature Applications**: Prioritize YW or YN grades to leverage their heat resistance and mitigate tool failure.

4. **Precision Requirements**: For finishing operations, materials with a fine-grained microstructure (such as YG6X or YN10) should be selected to reduce surface roughness.

The classification system for cemented carbides is fundamentally rooted in the precise alignment of material properties with machining requirements. From rough machining of cast iron to finish milling of nickel‑based alloys, and from conventional lathes to five‑axis machining centers, the technological evolution of cemented carbides has consistently revolved around three overarching goals: enhancing efficiency, reducing costs, and expanding process boundaries. With advances in powder metallurgy—such as ultrafine grain technology and gradient microstructure design—the performance limits of cemented carbides will continue to be pushed, providing increasingly robust material support for intelligent manufacturing.

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