Effect of microstructural evolution on the creep properties of carbon and boron modified SX alloy RR2072

Abstract

The relationship between microstructural evolution and creep properties of carbon and boron modified single crystal superalloy RR2072* has been investigated. Three kinds of single crystal specimen were prepared for comparative study; fully solutionized base alloy, partially solutionized base alloy, and the carbon and boron modified alloy. Creep and thermal exposure tests of the single crystal specimens were performed at 950 degreesC and 1050 degreesC. Addition of carbon and boron to the base alloy RR2072 made it difficult to bring the existing phases into solution. Partial solutionizing of the existing phases decreased the creep resistance of the single crystal. However, carbon and boron retarded precipitation of the sigma phase under both creep and thermal exposure conditions. Owing to the delayed precipitation of sigma phase, the creep properties of the modified alloy were similar to those of the base alloy.