The potential of tungsten-2 percent thoria, 218 tungsten, and tungsten-1 percent thoria wire reinforced nickel-base superalloy composites for turbine bucket applications was evaluated based on stress-rupture strength, oxidation, and impact resistance. The results indicate that refractory metal alloy fiber-superalloy composites have potential for turbine bucket use based on the properties measured. Composites were produced having stress-rupture properties superior to conventional cast superalloys at use temperatures of 2000 and 2200 F. The 100 and 1000-h stress-rupture strength of the composite at 2000 F was 49,000 and 37,000 psi, respectively. A few thousands of an inch of matrix or cladding material was found to be sufficient to protect the fibers from oxidation at 2000 F for times up to 300 h. At 300 F and above the impact resistance of the composite compares favorably with that of superalloys.

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The impact properties of copper, copper-10 nickel, and a superalloy matrix reinforced with tungsten fibers were studied. In most cases, the following increased composite impact strength: increased fiber or matrix toughness, decreased fiber-matrix reaction, increased test temperature, hot working and heat treatment. Notch sensitivity was reduced by increasing fiber or matrix toughness. The effect of fiber content depended on the relative toughness of the fibers and matrix. Above 530 K a 60 volume percent superalloy matrix composite had a greater impact strength than a turbine blade superalloy, whereas below 530 K a hot worked 56 volume percent composite had a greater impact strength than the superalloy.

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