| 摘要 |
PURPOSE:To manufacture an oxidation-resistant W-base sintered alloy combining low coefficient of thermal expansion with sufficient ductility, by sintering a green compact of a powder mixture having a specific composition consisting of W powder, Ni powder and Fe powder and diffusing Cr under specific conditions. CONSTITUTION:The powder mixture consisting of, by weight, 85-95% W powder and the balance powders of Ni and Fe in which the weight ratio of Ni to Fe is regulated to 1:1-4:1 is compacted at a pressure of about 1.0-1.5 ton/cm<2>. The resulting green compact is sintered in a reducing atmosphere at a temp. higher than the melting temp. of an Ni-Fe phase by 20-60 deg.C. It is preferable that sintering time is set up so that W grains are regulated to about 20-100mum. Subsequently, Cr is diffused into the sintered compact at 1,420-1,500 deg.C. This diffusion can be carried out in a powder mixture of Cr powder and Al2O3 powder. In this way, the W-base sintered alloy excellent in oxidation resistance can be obtained.
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