Property and application of tungsten carbide

Tungsten - carbon binary system can form two kinds of crystal type of carbide, WC and W2C. WC is not only the main materials for cemented carbide making, but also is the important raw material powder for the preparation of high wear-resistant coating in thermal spraying field. It is featured with high hardness, especially the high temperature hardness. WC can be wetted by C0, Ni, Fe and other metallic melt, Co solution is the best. The mouth can be dissolved in the metallic melts when the temperature are raised above the metal melting point, and falling the temperature can precipitate excellent performance of WC0, making it being material binding phase with drill or nickel and other metal, through high heat sintering or coating process, forming good wear-resisting coating.

Poor resistance to high temperature oxidation is the main disadvantage of WC, it suffers severe oxidation In 500 ℃ ~ 800 ℃ air, we can do preliminary protection for WC particles by coating of heat-resisting and antioxidant metal, or improving the property of heat-resisting and oxidation resistance of WC by forming a composite carbides with TaC, Tic and other solid solutions. WC  heated to 2850 ℃ is still stable in Ar atmosphere, it’s also not affected in the high temperature nitrogen.

Melting point and hardness of W2C are higher than WC, It can form eutectic mixture with WC W2C + WC, Lower melting point, easy casting, this is so called “cast tungsten carbide” or “fusible tungsten carbide”, the average carbon content is 3.8% ~20%<quality>,  W2C is 78% ~ 80% <quality>and WC is 20% ~ 22%<quality>. This kind of cast tungsten carbide is one of the hardest and the most wear-resist materials, and lower costing.

WC powder can bond with co-based powder, Ni-based powder, fe-based self molten alloy powder and Ni- Al bonding composite powder, which is widely used in the preparation of wear-resistant coating, especially in abrasive wear-resistance, Hardfaced wear, clay sand erosion wear and other aspects. Tungsten carbide  powder is mainly used as the material of thermal spray powder.

We can spray the wear-resistant coating with Vacuum plasma spraying and protective atmosphere plasma spraying, but coating adhesive force is not very good. 

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Different kinds of thermal spray powder

Ni-based self-melting alloy powder, which is based on Ni and composing of Chromium, boron, silicon, carbon, copper, molybdenum and other elements. The melting point of alloy powder is low, good self-molten performance, and it’s with good properties of corrosion resistance, abrasion resistance, heat resistance, oxidation resistance and others, it’s the most widely used welding alloy powder.

WC Based Tungsten Carbide Thermal Spray Powders: High hardness, great wear-resistant, erodent-resistant and concussion-resistant, Well-proportioned grain, great apparent density and high density. Good capability of spray-welding. And there four kinds of it, depending on its elements: WC -6Co, WC -10Co-4Cr, WC -12Co, WC -17Co spray powder.

There are two kinds of Fe-based alloy powder, one kind is stainless steel, containing more nickel and chromium; the other kind is high-chromium iron, containing more chromium and carbon.

Cobalt-based self-melting alloy powder, which is based on Co and composing of Chromium, tungsten, nickel, boron, silicon and other elements. It has the characteristics of Good High Temperature Performance, good red hardness, excellent wear-resistance and oxidation resistance.

Cu-based self-melting alloy powder, which is based on Cu and composing of Nickel, chromium, boron, silicon, manganese and other elements. It’s featured by high mechanical performance, easy machining, excellent corrosion resistance and Low friction factor.

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Property of HVOF spraying coating

High velocity oxygen fuel spraying, as a branch of surface engineering technologies, is a newborn technology of surface strengthening and protection, developing rapidly at home and abroad in three decades.

 

Its dominating characteristic is can spray all kinds of metal and alloy, ceramic and metal ceramic, plastic, nonmetallic mineral and almost all kinds of solid engineering materials. Many kinds of functional coatings are made through it, such as wear resisting, anti-corrosion, heat resistance, anti-oxidation, thermal insulation, insulation, conductive, anti-radiation, anti-interference, transformation.

HVOF spraying is a low input, high-yield project, protecting equipment through spraying and surface strengthening, or repairing used and utilizing waste can longer its service life. HVOF spraying is widely used in many industries, such as modern machinery manufacturing industry, power industry, metallurgical industry, automobile industry, aviation industry, petrochemical industry, paper industry.

Property parameter of HVOF spraying coating

Thickness: Q0.05～2mm

Hardness: HV900～1300

Bonding strength: ≥90MPa

Porosity: ≤1%

Surface roughness: after polishing can be as smooth as mirror（Ra within 0.2）

Anti-corrosion of Acid, alkali, salt, hydrothion, etc.

Temperature resistance: 1200℃

And based on my experience, you can purchase excellent HVOF spraying powder from Chengdu WOCO Cemented Carbide Industry Co.Ltd at a competitive price, it’s a professional china powder sprayer manufacturer.

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