Surface wear resistance and microstructure characteristic in longitudinal–torsional ultrasonic vibration side milling of GH4169 superalloy

Abstract

The intrinsic link between the surface wear resistance and microstructural evolution of a material was revealed. The surface wear resistance of the GH4169 superalloy was systematically investigated in relation to the surface machining topography and mechanical properties at different cutting widths in conventional side milling (CSM) and longitudinal–torsional ultrasonic vibration side milling (LTUVSM). The wear resistance was evaluated by analyzing the wear topography, friction coefficient, duration of the initial wear stage (IWS), and wear volume of dry sliding wear. The specimens in LTUVSM exhibited higher wear resistance than those in CSM owing to the inhibition of friction and growth of inter-surface friction nodes by the uniform ultrasonic vibration texture (UVT) and the inhibition of subsurface crack nucleation and extension by the superior mechanical properties. The mechanism of the ultrasonic vibration intervention in grain refinement was revealed. The involvement of ultrasonic vibration enhanced the dislocation accumulation, the grain boundary fractures, and increased the recrystallization fraction, which resulted in a thorough grain refinement with a 7.3 % decrease in average grain diameter (AGD) relative to that obtained with CSM. The increased grain refinement in LTUVSM improved the mechanical properties of the surface-layer material, thereby improving the wear resistance of the specimen.