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Gaurav Aggarwal, doctoral candidate in engineering
science and mechanics, will present the team's work in a paper,
Development of Niobium Powder Injection Molding, at the International
Symposium on Tantalum and Niobium in Pattaya, Thailand, Oct. 17. His
co-authors are Seong J. Park, research associate in engineering
science and mechanics, and Dr. Ivi Smid, associate professor of
engineering science and mechanics, who is Aggarwal's thesis adviser.
Aggarwal notes that other researchers have
developed techniques for processing niobium via powder metallurgy and
some have applied powder injection molding to niobium-based alloys and
superalloys. However, the Penn State team is the first to explore
processing pure niobium via powder injection molding. They have
developed a method to calculate the optimal proportions of niobium
powder to binder in feedstocks as well as the appropriate temperature
and duration for sintering.
The team's method for calculating the optimal metal
powder/binder proportions also can be applied to other materials which,
like niobium, have irregularly-shaped particles.
Aggarwal points out that pure niobium products are
currently formed from powders and, therefore, there is no powder cost
penalty as in ferrous materials, for example. Although it is
biocompatible and benign in use, niobium is difficult to control at
the high temperatures needed to process it because of its high
reactivity.
In the Penn State approach, powdered niobium is
mixed with the appropriate binder in proportions roughly 92 percent
niobium by weight and 8 percent binder by weight. The feedstock is
then processed in a standard injection-molding machine.
The resulting part is placed in a solvent that
dissolves out the binder and then is heated to drive off the solvent
and any remaining binder. The part is then processed in a sintering
furnace.
The researchers have validated their approach
experimentally. The injection temperature and pressures were
determined for optimal filling time based on simulation. |
