Effect of Heat Treatment on Microstructure and Tensile Properties of a New Type of Ni-based Superalloy Designed for Additive Manufacturing

The effects of different heat treatment processes on the microstructure and properties of a new type of Ni-based superalloy ZGH451 were studied. The results show that the as-deposited microstructure is mainly composed of epitaxial micro- columnar grains, and there is gamma/gamma' eutectic exists among the interdendritic region. The segregation of element in the alloy results in the size difference of gamma' phase between dendritic region and interdendritic region, which are 100 nm and 250 nm, respectively. The microstructure and properties of the alloy are different with varying heat treatment processes: as the solution temperature increases from 1180 degrees C to 1350 degrees C, the segregation degree of the alloy decreases gradually until the initial melting microstructure is found at 1350 degrees C. With the first aging temperature increasing from 1050 degrees C to 1150 degrees C, the size of gamma' phase increases gradually, and its shape changes from spherical and other irregular shape to cube shape. In summary, the heat treatment process is optimized and the one suitable for the alloy (HT2) is obtained. Compared with the as- deposited alloy, the grain size of alloy is significantly increased after the complete heat treatment, and the segregation and gamma/gamma' eutectic of the alloy are eliminated. The denser dislocation network is formed at the gamma/gamma' interface during tensile deformation at 1000 degrees C. The tensile strength and yield strength are 520 MPa and 269 MPa, respectively, and the elongation is 11%.