Document Type : Original Article
Author
Department of Research and Development, UOP, England
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 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.
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