What is WC Powder (Sintered-Grade Tungsten Carbide)?
Tungsten carbide powder — chemical formula WC — is produced by carburising tungsten metal powder with carbon (usually as carbon black) at high temperature in a hydrogen atmosphere or vacuum. The product is a grey powder with a uniform crystal structure where each tungsten atom is bonded to one carbon atom. The stoichiometric carbon content is 6.128% by weight.
WC powder is the starting material for cemented carbide (hardmetal) — it is mixed with a metallic binder (typically cobalt, Co, at 3–25%) and pressed into near-net-shape parts that are then liquid-phase sintered at ~1,400°C to form the dense WC-Co composite. WC-Co is the material in cutting inserts, end mills, drill bits for machining, dies, and most precision wear components.
Key properties of WC powder: Hardness of WC crystal ~2,400 HV (monocrystalline); typical grain size F.S.S.S. 0.6–15 µm; carbon content 6.11–6.13% (bonded), free carbon max. 0.03%; apparent density 2.4–6.0 g/cc depending on grain size.
What is Fused Tungsten Carbide (W₂C Grit)?
Fused tungsten carbide is produced in a completely different way: tungsten ore (APT or WO₃) and carbon are co-melted in an electric arc furnace at temperatures exceeding 2,600°C. At this temperature, the material partially reduces and carburises, producing a eutectic melt of WC and W₂C (ditungsten carbide). The melt is then tapped and rapidly solidified into 'pigs' or cast ingots, which are crushed and sieved to produce angular grit particles in specific mesh fractions.
The resulting fused tungsten carbide is a two-phase material containing both WC and W₂C in a characteristic eutectic microstructure. Its total carbon content is approximately 3.5–4.1% by weight (significantly lower than stoichiometric WC), and its apparent density is approximately 5.90 g/cc. The angular, crushed morphology has an extremely high hardness of approximately 3,000 HV — higher even than sintered WC-Co — because the W₂C phase is harder than pure WC.
Fused WC (W₂C) grit is not used to make sintered carbide parts. It is used as a hard-facing material: embedded in brazing alloys (diamond tool matrices), weld overlay electrodes, and thermal spray coatings to protect surfaces against severe abrasion.
Chemical and property differences side by side
Crystal structure: WC powder is single-phase WC (hexagonal); Fused WC is a WC + W₂C eutectic two-phase structure.
Carbon content: WC powder has 6.11–6.13% C (stoichiometric); Fused WC has 3.5–4.1% C (sub-stoichiometric).
Hardness: WC crystal ~2,400 HV; Fused WC grit ~3,000 HV (W₂C is harder).
Apparent density: WC powder 2.4–6.0 g/cc (varies with grain size); Fused WC grit ~5.90 g/cc (dense angular particles).
Particle form: WC powder — fine, irregular or rounded particles in µm range, specified by FSSS; Fused WC — angular crushed grit in mesh fractions (30/40, 40/60, 60/80, 80/100, 100/120 mesh ASTM/BSS).
Primary use: WC powder → wet-milled into WC-Co slurry → pressed and sintered into cutting tools and wear parts; Fused WC → brazing into diamond tool matrices, OAW/MIG hard-facing electrodes, HVOF thermal spray.
When to use WC powder vs. Fused WC grit
Use WC powder (F.S.S.S. 0.6–15 µm, total C ≥ 6.11%) when: manufacturing sintered WC-Co cutting inserts, end mills, drill bits, dies, or wear components by conventional powder metallurgy; making thermal spray WC-Co composite spray powder for HVOF coating; or producing WC-based paste or PTA hardfacing where the material will be sintered in a furnace cycle.
Use Fused WC grit (mesh 30/40 – 100/120, carbon 3.5–4.1%, density ~5.90 g/cc) when: brazing diamond-impregnated segments for core bits, saw blades, and wire saw beads where W₂C grit is embedded in the metal matrix around diamond; hard-facing excavator bucket teeth, ploughshares, drill collar thread protectors, or pump impellers by OAW or MIG overlay welding; filling wear-resistant wear bars or cladding plates with a high-density abrasion-resistant grit phase.
The clearest practical rule: if the process involves liquid-phase sintering at ~1,400°C with cobalt, use WC powder. If the process involves brazing, weld overlay, or cold-setting in a metal matrix below 1,200°C, use fused WC grit.
What to check on the certificate of analysis
For WC powder: F.S.S.S. (µm), total carbon (min. 6.11%), free carbon (max. 0.03%), apparent density (g/cc), oxygen content (max. 0.10–0.15%), and metallic impurities (especially Fe, max. 50–100 ppm).
For Fused WC grit: mesh fraction distribution (percentage retained on each sieve), total carbon (3.5–4.1%), apparent density (min. 5.80–5.90 g/cc), and if used for diamond tool matrices — the W₂C/WC phase ratio by XRD if critical to sintering temperature compatibility.
Jayanth Tungsten supplies both WC powder (FSSS grades 2.5–15 µm) and fused WC grit (mesh 30/40 to 100/120), each with a full CoA covering the relevant parameters for the product type.