Microstructure and mechanical properties of fine-grained K417 superalloy ring fabricated by vacuum centrifugal casting

The K417 superalloy rings are extensively applied in the aerospace field for its excellent high-temperature strength and outstanding high-temperature creep resistance. However, conventional manufacturing routes face challenges in complex processing procedures and low material utilization. This work presents a vacuum centrifugal casting process to directly fabricate fine-grained K417 ring. Numerical simulation of grain structure established the correlation between processing parameters and microstructural development. Using the optimized processing parameters, the prepared K417 ring exhibits a fine grain structure (ASTM 4) with minimal porosity (below Grade one). No macrosegregation is observed with homogeneous element distribution throughout the ring. The y′ phase is uniformly distributed in the matrix as the main strengthening phase, accompanied by y/y′ eutectic phases and MC carbides precipitated at the grain boundaries. The tensile strength is 1,115.3 MPa at 20 °C, 725 MPa at 900 °C, and 409.6 MPa at 1,000 °C, with elongation of 10.4%, 8.5%, and 9.1%, respectively. Microstructural analysis indicates that cracks mainly originate near MC carbides and eutectic phases. As the tensile temperature increases from 20 °C to 1,000 °C, the fracture form gradually transitions from transgranular to intergranular fracture.