Effect of thickness on microstructure of thin-walled nickel-based single-crystal superalloy castings

Abstract

With increasing turbine inlet temperatures in aero-engines, the demand for temperature-resistant turbine blades has led to the widespread use of nickel-based single crystal superalloys. These alloys, known for their exceptional performance in high-temperature and high-stress environments, incorporate advanced cooling structures like lamilloy and double wall cooling to enhance temperature tolerance. As the development of aviation technology, thin-walled structures are widely used in turbine blades of aero-engines. However, the adoption of ultra-thin wall structures, particularly in lamilloy turbine blades with thicknesses of 0.5 mm or less, presents a significant manufacturing challenge and will cause the degradation of mechanical properties. This study delves into the growth and evolution of dendrites in the nickel-based single-crystal superalloy DD403, exploring thin-walled specimens with varying thicknesses during directional solidification. Findings reveal that decreasing wall thickness correlates with a reduction in average primary dendrite arm spacing, smaller γ′ precipitates sizes within the dendrite core and interdendritic regions, and reduced microsegregation levels of Al, Ti, Co and W. These insights contribute to optimizing thin-walled turbine blade performance in aero-engines applications.

Keywords

• Thin-wall structure
• Nickel-based single crystal superalloy
• Directional solidification
• Dendrite growth
• Segregation