COATED TUNGSTEN POWDER

KINETIC ENERGY WEAPONS EMPLOY TUNGSTEN PROJECTILES. FOR MAXIMUM EFFECTIVENESS THE TUNGSTEN MUST POSSES HIGH DENSITY, STRENGTH AND DUCTILITY. LIQUID PHASE SINTERING OF TUNGSTEN POWDER IN A MATRIX OF IRON AND NICKEL POWDER HAS BEEN EMPLOYED FOR THIS PURPOSE. PROBLEMS STILL EXIST. AS DENSITY APPROACHES THEORETICAL, BOTH DUCTILITY AND TENSILE STRENGTH ARE SACRIFICED. THE REASON SEEMS TO BE THAT AS THE MATRIX COMPONENT APPROACHES ZERO, A HIGH DEGREE OF CONTINGUITY OCCURS BETWEEN GRAINS, NON-UNIFORMITY OF THE MATRIX DEVELOPS DUE TO FLUCTUATIONS, AND DELETERIOUS IMPURITIES LIKE O(2), S AND P SEGREGATE ON GRAIN BOUNDARIES. WE PROPOSE TO MINIMIZE THESE ADVERSE EFFECTS BY COATING THE TUNGSTEN POWDER WITH THE MATRIX CONSTITUENTS FE AND NI BY MEANS OF CHEMICAL VAPOR DEPOSITION (CVD). THE EXTREME PURITY LEVELS AND UNIFORMITY OF DISTRIBUTION ATTAINABLE BY CVD CAN ALLEVIATE ALL THREE DELETRIOUS EFFECTS. THE INNOVATIVE PROCESS HEREIN DESCRIBED WILL ALSO PERMIT GRAIN SIZE CONTROL.