Medicine
Martin Viberman
Abstract
The process of hot extrusion of very fine cemented carbide powder with a combination of softener has been known for many years. This method has been successfully used for cermet’s to make simple prismatic shapes that have a large length to cross-sectional area ratio. Cylindrical and quadrangular ...
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The process of hot extrusion of very fine cemented carbide powder with a combination of softener has been known for many years. This method has been successfully used for cermet’s to make simple prismatic shapes that have a large length to cross-sectional area ratio. Cylindrical and quadrangular shapes and other sections can be easily made with this method, even making pipes is also possible. Depending on the plasticizer used (for example, polystyrene with the addition of dimethyl and diphenyl ether), the extrusion process requires temperatures between 160 and 175 degrees Celsius (320- and 350-degrees Fahrenheit). The process of complete and slow sticking under vacuum before full sintering is necessary and even vital to avoid stretching (from casting defects, from sagging), breaking or very small porosity. Twisting of bodies produced by extrusion similar to what happens in the plastic industry is acceptable for this process. In order to produce a high-quality product, hot pressing is necessary.
Medicine
Martin Viberman
Abstract
In the general field of cemented carbides, cobalt-bonded tungsten carbide groups are the category that has undergone the most development over the past three decades. Arrangements, physical properties, manufacturing methods and application of this class of materials have been reviewed in the cemented ...
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In the general field of cemented carbides, cobalt-bonded tungsten carbide groups are the category that has undergone the most development over the past three decades. Arrangements, physical properties, manufacturing methods and application of this class of materials have been reviewed in the cemented carbides article in this issue. In many applications, tungsten carbide bonded to cobalt has certain disadvantages. The properties of titanium carbide bonded to steel can be compared to the same material for tungsten carbide bonded to cobalt as follows: Titanium carbides bonded to steel respond to heat treatment and when the joint is in an annealed condition, it can be machined with conventional machines. Carbide bonded to fully hardened steel can be heated to a variety of temperatures. Hence, it obtains more ductility than tungsten carbide bonded to cobalt. Cemented tungsten carbides are materials with high modulus. Carbides bonded to steel have a modulus that is not greater than that of steel. The coefficient of thermal expansion of steel-bonded carbides is closer to that of steel than to cemented tungsten carbides. Both tungsten carbide and carbide products can be soldered.
