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In the first report, characteristics of sintering on Ni-P alloy coated tungsten powders were described. In the present study, authors examined sintering behaviors of Ni-P-W composite powders and the properties of compacts.The results were as follows;(1) By the chemical mixing, we obtained better compacts as compared with the mechanical mixing. However, it is expected that by improving the powder size and mixing condition the compacts of full density can be obtained even by the mechanical mixing.(2) The activation energy of densification of Ni-P alloy coated tungsten powder specimens was 41, 000cal/mol.(3) The transverse rupture strength of Ni-P alloy coated tungsten powder specimens were inferior to those of nickel coated tungsten powder specimens.(4) Tungsten pipes and blocks with tungsten contents of more than 99.5% were obtained in this way, and sintered densities of the compacts were more than 19g/cm3.

Tungsten-chromium sintered compacts were hot-pressed at 1450°C for 30 min in graphite moulds. Mechanical properties and high-temperature oxidation resistance of sintered compacts were tested. And also the improvement of oxidation resistance by small additions of Al and Si was tested.Results obtained are summarized as follows.(1) The density of the hot-pressed specimens were more than 95% of the theoretical value.(2) The hardness of the sintered compacts was HRC 56.6-63.0, higher than the hardness of tungsten.(3) Transverse rupture strengths of 30-40kg/mm2 were obtained.(4) The addition of Cr (>30 wt%) was found to improve the oxidation resistance.(5) (W-30 Cr)-Si alloy was suitable for tungsten-base high temperature materials.