2011 Volume 52 Issue 2 Pages 201-209
This study investigated the influence of rhenium on the mechanical behavior and fracture mechanism of a fine-grain Mar-M247 superalloy at elevated temperatures. Tensile test results showed that the addition of 3 mass% Re significantly improved the ultimate tensile strength and yield strength from room temperature to 760°C. Creep test results showed that steady-state creep behavior dominated creep properties under the test condition of 760°C/724 MPa. The steady-state creep rate and creep life of alloy with 3 mass% Re was reduced by 31% and prolonged by 63%, respectively, compared to alloy without Re. The improvement in tensile and creep properties in 3 mass% Re alloy was associated with a decrease in grain and γ′ size and an increase in strength of γ⁄γ′ matrix. However, adding 4.5 mass% Re resulted in a decrease in the tensile and creep properties due to the formation of needle-like P phase in the grain interior. Fracture analysis demonstrated that during tensile and creep tests, cracks initiated and propagated along grain boundary in alloy without Re and containing 3 mass% Re alloy; however, in the alloy containing 4.5 mass% Re, cracks initiated and propagated along grain boundary and the P phase/matrix interface. Under the current tensile and creep conditions, 3 mass% Re was an optimal addition for casting a fine-grain Mar-M247 superalloy.