Study on the As-Cast Microstructure and Homogenization Mechanism of GH3128 Superalloy

This study mainly introduces the microstructure and homogenization mechanism of the GH3128 as-cast superalloy. The experimental components include an examination of the composition of the precipitation phases in the alloy via Thermal-Calc software, field emission electron probe microscopy and X-ray diffractometry and the determination of the segregation status of elements between dendrites and interdendrites. The segregation status of elements after homogenization is determined by using one-stage and two-stage theoretical residual segregation indices, the microhardness variance and microscopic extreme value on the sample surface. Finally, the homogenization system is established by using diffusion kinetic analysis. The results show that the main precipitation phases in the alloy are composed of γ', M23C6, M2B, M6C, μ and σ phases. The main segregation elements include W, Mo, and Cr, and the degree of segregation is W > Mo > Cr. A comparison of the element segregation state after different homogenization treatments showed that when the homogenization system is 1130 °C for 12 h followed by 1210 °C for 36 h, the sample has lower microhardness variance and microscopic extreme value, the chemical composition in the inside of the sample is uniform and the concentration fluctuates minimally throughout. Therefore, the homogenization effect of the sample is optimal.