Effect of carbon content on the recrystallization of a single crystal nickel-based superalloy

Carbon has recently been reintroduced to single crystal (SX) superalloys because of its beneficial effects, such as reducing the occurrence of casting defects and enhancing the tolerance of low angle grain boundaries. Meanwhile, the addition of carbon leads to changes in the carbide morphology and volume fraction and may subsequently affect the recrystallization (RX) behavior. The purpose of this paper was to identify the effect of the carbon content on RX in an SX nickel-based superalloy. The SX specimens were prepared with an identical crystal orientation but different carbon contents. It was found that with the increase of the carbon content from 0.012 wt% to 0.17 wt%, the volume fraction of carbides increased linearly, while the average size of the carbides was nearly unchanged. After shot peening and heat treatment, a layer of RX grains was generated on the surface. As the carbon content was increased, the RX depth increased at first and later decreased. These changes were interpreted as the combined effect of the carbides on the stored energy during deformation and the pinning force during RX grain growth.