Feasibility of applying five-axis flank milling to nickel-based single crystal superalloy blade

To investigate the feasibility of five-axis flank milling for nickel-based single crystal (Ni-SX) superalloy blade, this study employed DD5 as a model material to systematically examine the influence of cutting speed (vs = 45.2, 67.8 and 90.4 m min−1) on the surface integrity, subsurface microstructure evolution and thermal stability. The surface roughness of DD5 blade first decreased and then increased with the vs increasing, reaching an optimum (Sa = 2.26 μm) at 67.8 m min−1. Beyond this speed intensified machining vibration degraded surface integrity and induced severe subsurface deformation composed of work hardening layer and plastic deformation layer. More critically, this milling-induced subsurface damage was identified as a key driver for microstructural degradation during thermal exposure. Specifically, after milling at 67.8 m min−1, exposure to 1200 °C, activated substantial precipitation of topologically close-packed (TCP) phases and the formation of large-scale cellular structures, resulting in the formation of a heat-affected zone exceeding 90 μm and a marked deterioration in mechanical performance in the DD5 blade. In contrast, the heat-affected zone remained below 34.9 μm at exposure temperatures lower than 1100 °C across all tested vs. By elucidating the correlations between flank milling parameters, subsurface damage and thermal stability, this work provides critical evidence and a theoretical basis for assessing the machinability and selecting service conditions for thin-walled Ni-SX superalloys.