Evolution Behavior of M₂₃C₆ Carbides Under Different Hot Deformation Conditions in Alloy 602 CA

Alloy 602 CA is a M₂₃C₆ carbides strengthened Nickel-based superalloy. In this alloy, M₂₃C₆ is different from that found in other superalloys because of its high volume fraction, wide size distribution and distinct precipitation locations. To investigate M₂₃C₆ evolution behaviors during hot deformation in Alloy 602 CA, a series of tests are carried out in this study. The test temperature ranges from 900 to 1100 °C and strain rate ranges from 0.001 to 0.1 s⁻¹, with a true strain of 0.7. It is found that hot deformation of the material decreases the distance between carbides which leads merging happening to change the morphology of primary M₂₃C₆. Secondary carbides mainly come from the dissolution of large primary carbides and precipitate along grain boundaries and twin boundaries which impede dynamic recrystallization (DRX) from happening. Volume fractions of M₂₃C₆ decrease from 900 to 1100 °C. At 900 °C and 1100 °C, the precipitation equilibrium is reached in the preheating period before hot deformation and deformation only change the size distribution of carbides. 1000 °C is a transition temperature where the volume fraction decreases as strain rate increases. The temperature rise initiated by adiabatic heating has a great influence on this precipitation behavior.