Effect of re-heat-treatment on the remnant creep life of a single crystal (SC) superalloy was investigated. It was found that the microstructure and the creep strengths of SC samples crept up to the early tertiary creep stage can be recovered by a re-solution treatment followed by two-step ageing treatment. The sample crept up to mid tertiary creep stage, however, was recrystalised during the solution treatment, resulting in a very low creep strength due to rupture at the created grain boundary. These results show that a simple re-heat-treatment can effectively improve the cost performance of SC components. This is in contrast with the case of conventionally cast (CC) alloys which needs hot isostatic pressing to eliminate the creep voids formed at grain boundaries.

SOURCE: Y.Koizumi, T.Kobayashi, H.Harada and T.Yamagata, Published in Proceedings of the Fourth International Charles Parsons Turbine Conference on "Advances in Turbine Materials, Design and Manufacturing", held at Newcastle upon Tyne, UK,4-6. The Institute of Materials, November 1997: pp. 679-684.

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