Penn State researchers have developed the first powder injectionmolding process for pure niobium, a biocompatible material similar toplatinum and titanium but cheaper.
The researchers, who are based in the University's Center forInnovative Sintered Products, say the new process could open the doortoinjection-molded niobium parts ranging from rocket nozzles, to wires,to human bone replacements, to orthodontic braces.
Gaurav Aggarwal, doctoral candidate in engineering scienceand mechanics, will present the team's work in a paper, Development ofNiobium Powder Injection Molding, at the International Symposium onTantalum and Niobium in Pattaya, Thailand, Oct. 17. His co-authors areSeong J. Park, research associate in engineering science and mechanics,and Dr. Ivi Smid, associate professor of engineering science andmechanics, who is Aggarwal's thesis adviser.
Aggarwal notes that other researchers have developedtechniques for processing niobium via powder metallurgy and some haveapplied powder injection molding to niobium-based alloys andsuperalloys. However, the Penn State team is the first to exploreprocessing pure niobium via powder injection molding. They havedeveloped a method to calculate the optimal proportions of niobiumpowder to binder in feedstocks as well as the appropriate temperatureand duration for sintering.
The team's method for calculating the optimal metalpowder/binder proportions also can be applied to other materials which,like niobium, have irregularly-shaped particles.
Aggarwal points out that pure niobium products are currentlyformed from powders and, therefore, there is no powder cost penalty asin ferrous materials, for example. Although it is biocompatible andbenign in use, niobium is difficult to control at the high temperaturesneeded to process it because of its high reactivity.
In the Penn State approach, powdered niobium is mixed withthe appropriate binder in proportions roughly 92 percent niobium byweight and 8 percent binder by weight. The feedstock is then processedin a standard injection-molding machine.
The resulting part is placed in a solvent that dissolves out the binderand 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 optimalfilling time based on simulation.
The project was supportedby the Center for Innovative Sintered Products and by Pennsylvania'sBen Franklin Technology Development Authority.
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