Research on the Microstructure Characterization and Fatigue Behavior of Nickel-Based Superalloy Subjected to Short-Arc and Milling Composite Processing

Short-arc machining is a novel electrical discharge machining method that utilizes high-energy arc discharge as the energy carrier. Due to its low cost and high processing efficiency, it has been widely applied in the efficient processing of superalloys. To address the challenges of efficient and high-precision processing of superalloys, a processing method combining short-arc machining with precision milling is employed. Advanced material characterization techniques such as electron backscatter diffraction (EBSD) are utilized to analyze the physical properties of the recast layer and surface crystal characteristics. High-temperature low-cycle fatigue life tests are conducted to investigate the correlation between fatigue life and typical surface integrity parameters (surface roughness, residual stress), as well as crystallographic parameters (grain size, grain orientation spread, geometrically necessary dislocations). Processing parameter optimization is achieved with fatigue life as the target. The results indicate that at high temperatures during short-arc machining, the surface material underwent recrystallisation to form a recast layer with a grain size reduction of 85.5% and a heat affected layer depth of over 400 μm. The trends in fatigue life are consistent with changes in residual stress, grain orientation spread and geometrically necessary dislocations. Selecting a larger axial depth of cut and lower feed per tooth is advantageous for achieving a higher fatigue life. The proposed research provides an instruction for high efficient precision machining of superalloys.