Tungsten carbide is a type of steel. It is comprised of mainly tungsten carbide and cobalt. The cobalt acts as a binder and improves shock resistance. As the percentage of cobalt in the mix rises, so does the shock resistance. These materials generally start as powders. A small amount of wax is then added to the mix. This holds the materials together so they can be molded. The mix is then placed in a de-waxing furnace overnight. It is removed and takes a more chalk like appearance. (S1, p1)As a result of this, a material is obtained which combines high strength, toughness and high hardness.
Tungsten carbide has very high strength for a material so hard and rigid. Its compressive strength is higher than virtually all melted and cast or forged metals and alloys. It has a tensile strength of 100,000-500,000 psi and a Brinell harness of 2570. (S3, p1) It has the highest melting point of any metal. It also has high thermal conductivity with a range of twice that of tool steel and carbon steel. A high resistance to corrosion enables it to be used in extreme conditions in or out doors. It also has a very high modulus of elasticity. Tungsten carbide is the hardest metal known to man. It has a hardness close to diamond. (S4, p1)
Tungsten carbide is known for its ability to retain an extremely sharp edge for an extended amount of time under certain cutting applications. It is also very brittle and is prone to nicking and chipping very easily. It is one of best-known materials for precision cutting. This is why one of the main uses for tungsten carbide is in a machine shop. Tungsten carbide can be fastened to other materials by any of three methods; brazing, epoxy cementing, or mechanical means. As prices go down and more and more technology is developed to use this material, machines and companies all over the world are reaping the benefits of having much stronger and longer lasting bits and blades.
There is a new procedure that was recently developed by Conforma Clad Inc. It is called Conforma Clad hard facing. Hard facing has been done in the past but not in the manner that Conforma Clad is doing it. This process enables manufactures to spray a mixture of tungsten carbide imbedded in a hard nickel-chrome matrix onto parts. By using this mix it forms a metallurgical bond with the substrate. The final product has bond strength of 75,000 psi. This cannot only be used on cutting tools but it can be sprayed onto parts of any shape or size. By hard coating a piece of equipment a company can greatly extend the life of the part. The less wear and tear on a part in a volatile area the better. Many companies will stand to benefit from this technology. The uses are endless.
In the November 4, 1999 issue of Machinedesign.com an online magazine a company wrote in and said the following about the Conforma Clad hard-faced coating. "Tungsten-carbide coatings extend component service life in one plastic plant's air conveyor system. The conveyor transports at high velocities palletized glass-filled nylon to storage bins for packaging and shipment. The system pipes, elbows, rotary feeders, and diverter valves were under constant bombardment by the pellets. Before being coated with tungsten carbide, component erosion within the conveyor, especially a diverter valve, caused unpredictable conveyor shutdowns. The plasma-spray-coated stainless-steel rotor in the original valve wore away causing catastrophic abrasion of the stainless part. But, coating the rotor and housing using a new process called Conforma Clad increased rotor lifetime throughput from 250,000 lb of pellets to over 300,000,000lb." (S2, p1) As you can see from this the system is very useful.
A company by the name of Nanodyne Inc. has discovered a way to produce the smallest grain of tungsten carbide cobalt powder on the market. The grain sizes range from 0.03 micron to 0.1 micron. The smaller the grain size the harder the end result can be and the stronger the tool will be. The grains are five times smaller than any other tungsten carbide on the market. This technology is now currently being used in the semi-conductor industry. Things like electrical contacts and circuit breakers are being greatly improved. (S6, p1, 2,3)
This technology is one to think about. If the cost of this process is cheap enough than surely in a few years all tungsten carbide will be made with these smaller grains. If the hardness of the material is affected that much than it won’t be long until someone else comes along and figures out a system to make tungsten carbide as strong as a diamond. If this were to ever happen it would change the way everyone machines parts.
Tungsten carbide’s main use is still for cutting tools. Machine shops all over the world use it every day. It seems that without this technology our world would be a different place. If you can think of all the things that are machined in this country every year it is amazing. Tungsten Carbide has been a huge contributor to the machining industry.
Tools made of tungsten carbide are stronger and last longer than hardened steel tools. Most of these tools just have tungsten carbide inserts brazed onto a hardened steel part or cutting tool. The sharp part is the tungsten carbide the rest of the tool is steel. This allows the tool to be strong and more flexible while still allowing the cutting surface to be sharp and stay that way. These tools cost less than a tool that is made of completely tungsten carbide.
Overall tungsten carbide is an amazing material. It has so many uses it is impossible to name them all. Every year more and more ways of putting it to good use are discovered. The harder and stronger we make parts and tools the longer they last. In the long run this saves everyone money. Tools and machinery have been using this technology for years and surely they will be using it in the future.
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6.Hassler, Darrel. New Nanodyne Plant to Produce Smallest
Tungsten Grain. Laurinburg, NC. Cahners Publishing Company,1998