Because they are liquid-phase sintered, W-Ni-Fe alloys typically sinter to densities of >99.5% of theoretical density. At tungsten contents above about 96% W, it becomes more difficult to achieve full density. Utilizing a designed experiment, this study determined the effect of various parameters on the density and sintered grain size of alloys containing 97.3% tungsten. Parameters included in the study were average tungsten particle size, pressing pressure, solid-state sintering temperature, nickel:iron ratio, and liquid-phase sintering temperature. Also a series of tests were run to determine the sensitivity of tungsten heavy alloys to impurities typically found in tungsten powder or introduced during processing. Copper, sodium, aluminum, chromium, and zinc were added at two levels to the tungsten oxide powder then reduced to the metal powder. Microstructural evaluation and mechanical properties were determined for bars sintered from W-Ni-Fe blends of these powders. The effect of quenching these materials was also investigated.
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