The influence of carbon addition on carbide characteristics and mechanical properties of CM-681LC superalloy using fine-grain process

This study investigates how carbon addition affects the carbide characteristics and mechanical properties of CM-681LC nickel-base superalloy with grain size of 80 μm prepared using the fine-grain process. Experimental results indicate that carbon addition from 0.11 wt% to 0.15 wt% greatly increases the amount of carbides, but the shape and size of carbides are similar due to the short solidification time of the fine-grain process, which limits the growth of carbides. The increase of carbides by proper carbon addition effectively improves the tensile strength by about 5% and the tensile elongation by over 30% at room and moderate temperatures (21–760 °C). The fracture analyses reveal that the carbon addition in fine-grain CM-681LC superalloy can changes the fracture modes from typical intergranular fracture modes to transgranular and intergranular mixed modes. The better carbon content of CM-681LC superalloy applied in the fine-grain process is 0.15 wt%, which has better mechanical properties.

Research highlights
► We examine the carbide characteristics by carbon addition in fine-grain process.
► Carbon addition increases the amount of carbides with appropriate shape and size.
► These changes of carbide characteristics effectively enhance tensile properties.
► The better carbon content of fine-grain CM-681LC superalloy is 0.15 wt%.