Sintering of mixtures of powders of nickel and molybdenum

Conclusions

• 1. Mixtures of powders of carbonyl nickel and molybdenum for preparing cermet alloys are easily pressed and sintered and do not require any special measures for protection from oxidation during sintering (careful drying of hydrogen and use of covers).

• 2. Cermet nickel molybdenum alloys obtained from mixtures of dispersed powders are practically homogeneous after sintering for 1–2 h at 1473°K. The processes of homogenization take place more actively in alloys obtained from mixtures of powders than in cast alloys.

• 3. With increase in molybdenum content in the alloy, beginning from 25%, there is observed a decrease in the rate of increase in electrical resistance which is connected with a denudation of the solid solution with molybdenum because of precipitation of intermetallic phases.

• 4. The strength of the alloys increases with increase in concentration of molybdenum. The cermet alloy Ni-30 Mo sintered at 1473 °K has a strength of 60 kg/mm² and an impact strength of 7.5 kgm/cm². The decrease in strength and impact resistance for alloys of Ni-35% Mo sintered at 1473°K is explained by embrittlement of the material because of precipitation of intermetallic phases along the grain boundaries.

• 5. After sintering at temperatures of above 1500°K, alloys of Ni-35% Mo have a greater strength than Ni-30% Mo alloys. The decrease in strength of Ni-30% Mo and Ni-35% Mo alloys sintered at 1573°K, compared with alloys sintered at 1523 °K, is explained by embrittlement of the material because of the sharp increase in grain size at 1573°K.