On the influence of carbides upon the microstructures and properties of a nickel-based cast superalloy

In the present study, varying amounts of carbides were incorporated in situ, with the aim of exploring their influence on the microstructural features and properties of the K4002 alloy. The results demonstrate that as the carbon content increases, both the quantity and size of carbides in the alloy increase. This is accompanied by an increased proportion of MC carbides and a reduced proportion of M 23 C 6 carbides. Compression tests conducted at 25 °C and 1000 °C reveal that the addition of carbon significantly enhances the yield strength and hardness of the alloy. Specifically, the average yield strength increases by approximately 30.4 % at room temperature and by about 22.1 % at 1000 °C. The strengthening of the alloy is primarily caused by the Orowan mechanism of γ' precipitates and the precipitation of carbides. The strengthening effect of both precipitation phases were calculated and compared with experimental values. The results show that the strengthening effect provided by the γ' precipitates is 186 MPa and that provided by carbides is 46 MPa, which are close to the experimental values. The CRSS for carbide fracture was calculated. The hindering effect on dislocations will reach its maximum when the carbide fracturing occurs. Modifying the carbon content in the K4002 alloy by in-situ precipitation of carbides is beneficial for improving its mechanical properties.