Abstract:The ultra-large-scale GH4738 superalloy turbine disk forging for power equipment, with a diameter exceeding φ1500 mm, represents the largest GH4738 alloy forging domestically. Using the Simufact numerical simulation software, the effects of process parameters such as friction coefficient, pressing speed, and initial forging temperature on the forming load and microstructure distribution of the forging were analyzed, and the optimal forging process parameters for the φ1500 mm-scale GH4738 alloy turbine disk were determined. Subsequently, numerical simulation and trial production of a scaled-down component were conducted using the same process parameters, and the actual microstructure distribution was found to be consistent with the simulation results. Based on the validated results, die forging of the φ1500 mm-scale GH4738 alloy turbine disk was successfully carried out on an 80,000-ton die forging press. After heat treatment, the microstructure and mechanical properties of the forging met the service requirements, achieving the engineering fabrication of the φ1500 mm-scale GH4738 alloy turbine disk forging. Furthermore, the precipitate phase content at different positions of the forging was quantitatively characterized using TEM. It was revealed that during the quenching process of the ultra-large-scale forging, the non-uniform solid-solution cooling rate at different cross-sectional positions—attributed to the size effect—resulted in a significantly higher content of secondary γ" precipitates on the surface than at the core after subsequent aging, leading to notable differences in tensile properties across different positions.