Tungsten Carbide Powder

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Tungsten carbide (WC) is an extremely hard, heat and wear resistant material made by mixing tungsten powder and carbon powder in a process called carburization. Tungsten carbide is one of the most important carbides and the most widely used in industrial and commercial applications.

Overview of Tungsten Carbide Powder

Tungsten carbide powder, also known as cemented carbide, is a composite material manufactured by mixing tungsten powder and carbon powder followed by sintering compacted powder blend in a protective atmosphere at temperatures of 1400-1500°C.

The resulting tungsten carbide material is characterized by exceptional hardness, wear resistance, strength, and toughness properties making WC an ideal material for cutting tools, mining and drilling where it frequently outperforms steel and where high stresses are encountered together with wear.

Tungsten carbide powders are produced in different grades of particle sizes, shapes, surface area and chemistries for use in diverse powder metallurgy, thermal spray, welding and hardmetal/cemented carbide applications across industry.

Tungsten Carbide Powder Types

Type Description
Macro grain WC powder For heavy machining applications requiring good wear resistance. Particle size > 1 micron
Micro grain WC powder Widely used for toughness in mining tools and drill bits. Particle size 1-0.5 microns
Ultrafine grain WC powder High hardness applications like cutting tools, die inserts. Particle size < 0.5 microns
Nanometer WC powder Specialist applications demanding maximum abrasion resistance. Particle size under 100 nm

Composition of Tungsten Carbide Powder

Tungsten carbide is composed of atoms of tungsten (W) and carbon (C) in a one to one ratio. It has the chemical formula WC, and a molecular weight of 195.86 g/mol.

The composition and structure of cemented carbides can be varied to optimize properties for different applications. Small amounts of other carbides or metals are frequently added. Some common additives are listed below:

Additive Function Typical Amount
Cobalt Binder metal 3 – 25 wt%
Titanium carbide Grain growth inhibitor 0 – 8%
Tantalum carbide Thermal shock resistance 0 – 8%
Niobium carbide Wear resistance 0 – 8%

Properties of Tungsten Carbide

Tungsten carbide possesses substantially superior properties compared to high speed steel and make it ideal for applications requiring high wear resistance.

Some key properties are outlined below:

Property Tungsten Carbide Value
Density 14.95 g/cm<sup>3</sup>
Melting point 2870°C
Hardness 88 – 93 HRA
Compressive strength 5.52 GPa
Fracture toughness 10 – 15 MPa√m

The exceptional hardness, wear resistance, strength and thermal properties allow it to outperform steel in challenging mechanical, mining, machining and drilling applications.

tungsten carbide powder

Characteristics of Tungsten Carbide Powder

The characteristics and quality metrics used to assess tungsten carbide powders are shown in the table below:

Characteristic Typical Specification Significance
Carbon content Typically 6.09 – 6.13 wt% Carbon provides the hardness
Oxygen content < 0.5 wt% High oxygen can reduce hardness
Total impurities < 0.4 wt% Impurities reduce density and hardness
Particle size 0.2 to 15 microns Submicron sizes enhance properties
Specific surface area 0.4 to 5 m<sup>2</sup>/g Higher values promote sintering
Morphology Angular, rounded Rounded/spherical powders have better flowability

Controlling powder characteristics like particle size distribution, purity levels, surface area, morphology and microstructure is essential for achieving dense compacts and consistent product quality after sintering.

Applications of Tungsten Carbide

The unique properties of extreme hardness, wear resistance, high strength, and thermal shock resistance lend tungsten carbide to be extremely widely used across applications including:

Tungsten Carbide Applications

Industry Examples of WC Applications
Mining Drill bits, drag bits, impregnated diamond bits
Machining Cutting tools, inserts, end mills
Construction Masonry drills, saw tips, earth boring tools
Manufacturing Extrusion dies, forming tools, pelletizer knives
Automotive Fuel injection nozzle tips, brake pad abrasives
Electronics Circuit board drills, wire drawing dies

Tungsten carbide maintains its hardness at elevated temperatures far better than other abrasion resistant materials. This allows it to cover an exceptionally wide range of applications across industry.

Tungsten Carbide Powder Specifications

Tungsten carbide powder is produced in a range of particle size distributions, purity levels, surface area specifications, oxide levels and morphology grades to meet application needs:

Specification Typical Range Significance
Particle size 0.2 to 15 microns Submicron for best properties. Match to application
Carbon content 6.09 – 6.13 wt% Essential for mechanical properties
Total impurities < 0.4 wt% High purity prevents defects
Specific surface area 0.4 to 5 m<sup>2</sup>/g Higher values promote sintering
Oxide (O2) level < 0.5 wt% Oxides reduce hardness and fracture resistance
Cobalt 3 – 25 wt% Binder phase. Varies to optimize strength, hardness and/or toughness
Grain growth inhibitors Titanium carbide, tantalum carbide etc Help control microstructure

International standard test methods like ISO 4499 are used for analysis and testing of cemented carbide powders. Common methods are wet analysis, XRD, particle size analysis using laser diffraction techniques.

Grades of Tungsten Carbide Powder

Tungsten carbide is categorized into grades based on properties, manufacturing method, quality level, end use or other specifications:

Grade Description Common Uses
Micrograin WC 0.5-1 micron powder Toughness for mining, construction tools
Ultra fine grade WC Micron to submicron powder Hardness for cutting inserts, dies
Rotating bending strength Classified by transverse rupture strength Mining and construction applications
Wear resistance grade Related to abrasion resistance Wear parts, dies, cutting inserts
Chemical vapor deposited (CVD) coated Uniform pure WC coating 1-50 microns thick High performance wear parts

International standards help define tungsten carbide grades for composition, properties, manufacture and testing including ISO 513 and ASTM B776.

Global Standards for Tungsten Carbide Powder

The widely accepted global standards for composition, testing, analysis and classification of tungsten carbide powders are shown below:

Global Tungsten Carbide Standards

Standard # Standard Title
ISO 513 Cemented carbides – Determination of transverse rupture strength
ISO 3326 Cemented carbides — Determination of oxygen content by fusion — Infrared detection method
ISO 4499 Cemented carbides – Determination of carbon content – Infrared detection method after combustion in an induction furnace
ASTM B388 Standard Specification for Thermomechanical Controlled Billets of Tungsten-Copper Composite Rod
ASTM B776 Standard Specification for Hafnium Powder and Hafnium Alloy Powder

These global standards for material composition, testing procedures, sampling, analysis and specifications facilitate quality control and technical understanding between international manufacturers, distributors and end users.

Suppliers of Tungsten Carbide Powder

Tungsten carbide powder is commercially manufactured by several leading suppliers globally. Some major WC powder producers include:

Company Headquarters Location
Sandvik Stockholm, Sweden
Kennametal Latrobe, PA, USA
Guangdong Xianglu Tungsten Ganzhou City, China
Japan New Metal (JNMET) Nagoya, Japan
Wolfram Company Schwäbisch Gmünd, Germany

Consumers can procure tungsten carbide powders directly from producers or through several specialty distributors and resellers globally. When selecting a WC grade, consider factors like application requirements, price point, lead times, certifications, and prior supplier relationship.

Pricing for Tungsten Carbide Powder

Tungsten carbide pricing depends on several parameters like particle size, carbon content, morphology, surface area and purchase quantity. Some typical tungsten carbide powder costs are shown below:

Type Price Range
Micrograin WC powder $27 – $45 per lb
Nanoscale WC powder $160 – $240 per lb
Rotating bending strength grade ~$33 per lb
Chemical vapor deposited WC $80+ per lb

Pricing also depends on distribution channel – buying directly from a manufacturer provides lower pricing compared to purchasing from a reseller or distributor. Larger purchase volumes also enable negotiated supplier discounts in most cases.

Comparison of Tungsten Carbide to Other Hard Materials

Tungsten carbide has exceptionally high hardness and wear performance compared to other industrially important materials:

Material Hardness (Vickers) Wear Resistance Fracture Toughness
Tungsten carbide 2500-3500 HV Excellent Moderate 10-15 MPa√m
Titanium nitride 2000-2200 HV Very good Low at ~6 MPa√m
Alumina ceramics 1800-2200 HV Good Low to moderate
Tool steel 650-850 HV Moderate Higher than WC
Stainless steel 150-300 HV Low Excellent

Among all commonly used materials, cemented carbide possesses the best combination of hardness, wear performance and fracture toughness – enabling it to cover the broadest range of demanding industrial applications.

Advantages of Using Tungsten Carbide Powder

Utilizing tungsten carbide provides significant benefits including:

  • Extremely high hardness – allows outstanding wear performance in mining, machining etc
  • Strength and fracture toughness superior to ceramics
  • Maintains hardness at high temperatures – stays rigid at 800°C
  • Resists corrosion in acidic/alkaline environments
  • High thermal conductivity aids heat dissipation from cutting edges
  • Range of material grades available to optimize properties

The unique performance properties of tungsten carbide powders make it a critically enabling material across production engineering.

tungsten carbide powder

Limitations of Tungsten Carbide Powder

Despite the advantages, tungsten carbide use also has certain restrictions:

  • Brittle failure – Sudden cracking under high loads due to low strain tolerance
  • High materials costs – Tungsten is relatively rare and WC manufacturing requires extensive processing
  • Low thermal shock resistance – Risk of cracking when subjected to sudden high temperatures
  • Limited chemical resistance – Dissolves in highly alkaline hot sodium hydroxide solutions
  • Difficult recycling – Reclaiming tunsgten scrap has low yields

By understanding limitations relating to brittleness, cost or environmental stability, end-users can make informed selections of appropriate tungsten carbide grade for their specific application requirements.

Frequently Asked Questions

FAQs about Tungsten Carbide Powder

Question Answer
What is tungsten carbide powder made of? Tungsten carbide powder is made by mixing pure tungsten powder and carbon powder in a ball mill. Powder is milled together with an organic wax binder and pressed into a compact before sintering at 1500°C in hydrogen to form WC.
Why is tungsten carbide so hard? Extreme hardness results from unique interatomic bonding where carbon atoms fit into interstices between tungsten atoms – forming an incredibly hard and stable crystal lattice structure.
What is the difference between tungsten and tungsten carbide? Tungsten is a pure metal with density of 19 g/cm3 while tungsten carbide is a composite made with tungsten and carbon atoms. Tungsten itself is relatively soft while WC is amongst the hardest materials known.
How strong is tungsten carbide? Tungsten carbide has extremely high hardness at 2500-3500 Vickers, compressive strength over 5 GPa and flexural strength ~2-3 GPa – much higher than almost any steel.
Is tungsten carbide brittle? Tungsten carbide grades have relatively low fracture toughness and strain tolerance, making them susceptible to sudden brittle cracking under high loads beyond material strength limits. Proper design is essential to avoid this.
Is tungsten carbide expensive? Tungsten carbide costs significantly more than tool steel due to extensive processing of tungsten ores but matches performance justify higher prices for wear critical applications like cutting inserts.

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