Pronounced impact of size and shape effects on creep rupture life of a K439B superalloy combustion chamber casting simulator

The size and shape effect (SSE) of components has become a critical issue for mechanical properties, application reliability, and processing. In this study, the creep rupture life (CRL) of components with different wall thicknesses and positions in a combustion chamber casing simulator made of K439B superalloy was investigated. The intrinsic mechanisms of the SSE were explored from the dendrite structure, volume fraction and size of the γ′ phase, and element segregation, etc. It is shown that this casting exhibits a strong SSE of creep rupture life, characterized by a significant difference in the CRL values up to 60% with the variation of wall thickness and position in the casing. In terms of casting technology, the influence of SSE on CRL is actually determined by the cooling rate. The SSE on the creep rupture life originates from the dendrite structure (such as the secondary dendrite arm spacing), volume fraction size of the γ′ phase in the dendrite trunk, and elements segregation rate. This work may have implications for the design and application of engineering components with large sizes and complex structures.