METAL INJECTION MOLDING OF TUNGSTEN HEAVY ALLOYS

TUNGSTEN HEAVY ALLOYS ARE METAL MATRIX COMPOSITES (MMC'S) HAVING UNIQUE COMBINATIONS OF STRENGTH, DUCTILITY AND DENSITY. THEIR FINAL MICROSTRUCTURE CONSISTS OF A CONTIGUOUS NETWORK OF TUNGSTEN GRAINS EMBEDDED IN A MATRIX OF A TUNGSTEN-NICKEL-IRON ALLOY. THE MAJORITY OF THEIR MILITARY APPLICATIONS REQUIRE A COMPLEX SHAPED FINAL FORM THAT IS GENERALLY OBTAINED BY MACHINING WHICH IS COSTLY AND RESULTS IN THE LOSS OF EXPENSIVE MATERIAL. METAL INJECTION MOLDING (MIM) IS A PROCESS IDEALLY SUITED FOR PRODUCING COMPLEX SHAPES. IT WOULD BE OF GREAT ADVANTAGE IF MIM CAN BE USED TO SUCCESSFULLY RETAIN THE UNIQUE PROPERTY COMBINATION OF TUNGSTEN HEAVY ALLOYS, WHICH ARE EXTREMELY SENSITIVE TO PROCESSING CONDITIONS, IMPURITIES, AND POST SINTERING TREATMENTS. THE TECHNICAL FEASIBILITY OF MIM AS AN ECONOMIC MANUFACTURING METHOD FOR TUNGSTEN HEAVY ALLOYS INTO NET COMPLEX PARTS WILL BE ANSWERED DURING THIS RESEARCH. PHASE I WILL ADDRESS THE KEY ISSUES OF: POWDER-BINDER MIXING, OPTIMUM SOLID LOADING OF THE BINDER, ALLOY ADDITIVES, INJECTION MOLDING, DEBINDING, PROPER SINTERING AND HEAT TREATMENT SCHEDULE, EVALUATION AND COMPARISON OF THE TENSILE PROPERTIES WITH CLASSIC PRESS/SINTERED ALLOYS, AND MICROSTRUCTURAL ANALYSIS.