Part 2: Preparation Process of Cemented Carbide
Chapter 4: Raw material selection and powder preparation
Tungsten Cemented Carbide is made of tungsten carbide (WC) as the hard phase and cobalt (Co) or nickel (Ni) as the bonding phase through powder metallurgy. Its properties (hardness HV 15002500±30, toughness K₁c 820 MPa·m ¹ / ² ± 0.5 , compressive strength>4000 MPa±100 MPa) are directly dependent on the quality of raw materials and powder preparation process. Raw material selection and powder preparation are the basis of cemented carbide production, which determine the microstructure (WC particle size 0.110μm±0.01μm, Co distribution uniformity>95%±1%) and final performance (thermal conductivity 80120 W/m·K±5 W/ m·K , corrosion resistance pH 212).
This chapter analyzes in detail the synthesis of tungsten carbide powder, the selection of binding phase and additives, powder pretreatment technology and powder characterization methods, covering process parameters, scientific principles, influencing factors, optimization strategies and engineering applications.
Powder preparation requires precise control of WC particle size (0.110μm±0.01μm), purity (free carbon <0.1%±0.01%), bonding phase characteristics (Co/Ni purity>99.8%±0.01%) and powder fluidity (1316 seconds/50g±0.5 seconds) to ensure sintering density (>99%±0.1%) and performance consistency (hardness deviation <±30 HV). For example, submicron WC powder (<0.5μm±0.01μm) can increase the hardness of the tool to HV 2300±30 and extend the aviation cutting life to 15 hours±1 hour; high-purity Co powder (>99.9%±0.01%) enhances the toughness of the drill bit ( K₁ c > 18 MPa·m ¹ / ² ± 0.5), and the mining life exceeds 1200 m±100 m.
the performance in Chapter 3 through the source of WC hardness (HV 2000 – 3000±50) and the contribution of Co toughness ( K₁c 1520 MPa·m¹ / ² ± 0.5 ), providing a theoretical and process basis for subsequent forming and sintering (Chapter 5).
4.0 Overview of cemented carbide types and raw and auxiliary materials
Cemented carbide is a high-performance composite material with tungsten carbide (WC) as the hard phase and cobalt (Co) or nickel (Ni) as the bonding phase. It is widely used in cutting tools, molds, wear-resistant parts and other fields. According to different application requirements and performance characteristics, cemented carbide can be divided into general type (YG series), heat-resistant/wear-resistant type (YT series), high toughness/impact-resistant type (YW series), nickel-based cemented carbide (YN series), high entropy alloy type and special type for additive manufacturing . The types and proportions of raw and auxiliary materials vary depending on the type of cemented carbide and the preparation process. Generally, they can be divided into three categories: main raw materials, auxiliary raw materials and auxiliary materials. The selection and use of these materials must strictly follow relevant standards to ensure product quality and process consistency.
4.0.0 Main types of cemented carbide
The following table lists in detail the main types of cemented carbide and their characteristics, process requirements, application areas and standards followed, reflecting its diverse application scenarios and process requirements.
| type | Main ingredients and features | Process requirements | Application Areas | Standard requirements |
| YG Series | Mainly composed of WC and Co, supplemented by carbon black, with high hardness and toughness | Strictly control the sintering atmosphere and temperature to prevent the introduction of impurities | Cutting tools (such as turning tools, milling cutters) | Comply with GB/T 5314-2011 sampling requirements and follow GB/T 26048-2010 sintering process |
| YT Series | Add TiC , paraffin lubrication is required to improve formability, high temperature resistance and wear resistance | Control sintering atmosphere and temperature to avoid impurities | High-speed cutting (such as steel processing) | Comply with GB/T 5314-2011 sampling requirements and follow GB/T 26048-2010 sintering process |
| YW Series | Contains TaC and/or NbC , requires argon protection, has both toughness and high temperature performance | Ensure the purity of argon atmosphere and precisely control the temperature | Heavy-duty dies (such as stamping dies) | Comply with GB/T 5314-2011 sampling requirements and follow GB/T 26048-2010 sintering process |
| YN Series | Replace Co with Ni and add TiN to achieve excellent corrosion resistance | Control sintering atmosphere and temperature to prevent oxidation | Corrosion resistant environment (such as chemical equipment) | Comply with GB/T 5314-2011 sampling requirements and follow GB/T 26048-2010 sintering process |
| High Entropy Alloy | Multi-element combinations (such as Cr, V, Mo, W, Ta) require precise mixing and HIP process to ensure uniformity | Accurate ratio, HIP sintering requires controlled high pressure (50-100 MPa) | Extreme environments (such as high temperature and high pressure conditions) | Comply with GB/T 5314-2011 sampling requirements and follow GB/T 26048-2010 sintering process |
| Additive Manufacturing | Spherical powder, prepared by gas atomization, with surface treatment agents added to improve performance | Gas atomization process, strict control of atmosphere and temperature | Additively manufactured parts (e.g. aerospace components) | Comply with GB/T 5314-2011 sampling requirements and follow GB/T 26048-2010 sintering process |
| illustrate | All types must follow the sampling standards of GB/T 5314-2011 to ensure batch consistency, and the sintering process is carried out in accordance with GB/T 26048-2010, emphasizing the precise control of atmosphere and temperature to avoid the introduction of impurities. | |||
4.0.1 Main raw materials of cemented carbide
The main raw materials are the core components of cemented carbide, which directly affect its mechanical properties and service life. The following is an overview of the main raw materials:
Tungsten Carbide (WC, Tungsten Carbide):
Function: As a hard phase, it provides extremely high hardness (>2000 HV) and wear resistance, accounting for 70%-94% ( wt %) of the total composition.
Specifications: Purity ≥99.8%, grain size 0.2-5 μm (fine grains 0.2-0.5 μm , coarse grains >2 μm ).
Applicable scope: All carbide types.
Cobalt powder (Co, Cobalt Powder):
Function: As a traditional bonding phase, it enhances toughness and flexural strength. The content is usually 6%-25% ( wt %).
Specifications: Purity ≥99.9%, particle size 1-5 μm .
Scope of application: YG, YT, YW series and high entropy alloys.
Nickel Powder
Function: Replace cobalt as corrosion-resistant bonding phase, enhance oxidation resistance, content 5%-20% ( wt %).
Specifications: Purity ≥99.9%, particle size 1-5 μm .
Applicable scope: YN series and additive manufacturing types.
Other carbides:
Carbide ( TiC )
Improve high temperature resistance and crater wear resistance, content 5%-20% ( wt %), purity ≥99.5%, particle size 0.5-2 μm , suitable for YT and YN series.
Carbide ( TaC ) / Niobium Carbide ( NbC )
Enhance high temperature strength and deformation resistance, content 2%-10% ( wt %), purity ≥99.5%, particle size 0.5-3 μm , suitable for YW series and high entropy alloys.
4.0.2 Auxiliary raw materials
Auxiliary raw materials are used to optimize performance or adapt to specific process requirements. They can be flexibly selected according to the grade and application scenario:
Carbon Adjuster:
Carbon Black
Control the carbon balance to prevent the formation of η phase ( Co ₃ W ₃ C ) or free carbon, content 0.1%-0.5% ( wt %), purity ≥99%, particle size <1 μm , suitable for all types (especially liquid phase sintering).
Graphite
As a carbon source, adjust the carbon content to 0.1%-0.3% ( wt %), purity ≥99.5%, particle size 1-5 μm , suitable for YG series and additive manufacturing powders.
Rare Earth Elements:
Cerium (Ce) / Lanthanum (La)
Refine grains and improve bending strength. The content is 0.1%-0.5% ( wt %) in the form of oxides with a purity of ≥99.9%. It is suitable for fine-grained grades (such as YG6F, YN6F).
Nitride/Boride
nitride ( TiN )/tungsten boride (WB): Improve surface hardness and corrosion resistance, content 1%-5% ( wt %), purity ≥99.5%, particle size 0.5-3 μm , suitable for YT, YN series and additive manufacturing .
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