Abstract
For improving endurance temperature of superalloys, an investigation was carried out into mould conditions of vacuum casting procedure and into fabrication conditions of tungsten fibre reinforced cobalt-base superalloys.
Creep testing was performed for the test-pieces, which were prepared by the method found to be the optimum in the above experiment. The tungsten wire was 1 mm in diameter and the matrix alloy was X-45 or its modification with respect to tungsten content. The fibre content was 50%. The strength of the composites was considerably lower than that expected from the combination of the wire and the matrix when the tungsten content in the matrix was low. This was due to the partial dissolution of the wire into the molten alloy during casting.
The effect of the thermal degradation of the wire during fabrication on the strength of the composite decreased with the increase in testing period, because the rate of decrease in the wire strength was smaller for the wire which had once experienced a high temperature as compared with the wire which had not. Although nickel-induced recrystallization was not observed, growth of reaction zones as well as formation and growth of voids proceeded during creep testing. Their effect on the strength of the composite was possible.
