Powder metallurgy techniques are used for the production of refractory
metals, composite metals and porous metals and metal nonmetlas combinations and
more efficient production method for certain parts.The high melting points of
refractory metals make it impossible to use the conventional melting and
casting techniques. The use of powder method for the manufacture of tungsten
filament was described at the beginning of this chapter. This techniques only for
the practical method of producing molybdenum, tantalum and others metals of the
same group.
One of the outstanding uses of powder metallurgy is the combination of
hard metals in th metallic matrix, which serves as the basis for cemented
carbide products. In the production of cemented carbides in cutting tools, a
suitable mixtures of the carbides of tungsten, tantalum and titanium with
cobalt as a binder is compacted and presintered. In this condition metal can be
cut, machined and ground to the final shape. The compact is then subjected to
high temperature about 270°C. sintering operation during the liquid cobalts
bind the hard carbide particles into a solid piece. Cemented carbide tools are
noted for high compressive strength, red hardness and wear resistance. Since
they are relatively brittle, they are usually employed as bronzed on tips to a
steel tool. They are also used a liners for wear resistance applications.
Others Examples are Diamond impregnated, grinding flywheels, drill core
bits and dressing tools. These consist of a embedded in cemented carbides or
more plastic and alloys.
Author: Sidney H. Avner
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