Study on the evolution mechanism of subsurface defects in nickel-based single crystal alloy during atomic and close-to-atomic scale cutting

Nickel-based single crystal alloys are widely used in aerospace industry. From the point of view of defect evolution and energy change, the evolution mechanism of subsurface defects in the atomic and close-to-atomic scale (ACS) cutting single crystal nickel-based alloy with silicon nitride tool was studied, combining with the molecular dynamics method. The mixed potential function was used to describe the force interaction between atoms in the ACS cutting system. The process of nucleation, propagation and transformation of subsurface defects were analyzed. Based on the dislocation emission model, the relationship between dislocation slip length and change of energy was described. The variety, quantity and area of subsurface defect changes caused by the change of cutting speed, crystal orientation and cutting depth were discussed. The result shows that increasing cutting speed can effectively reduce the number and area of subsurface defects and improve the quality of machined parts. The larger the cutting speed, the larger the chip volume. With the increase of cutting depth, the number of stacking fault tetrahedrons in the subsurface area of workpiece increases. When crystal orientation 010001¯ is used for cutting, more defects will be produced in the subsurface region. When crystal orientation are 111101¯ and 011011¯, the dislocation emission angle is π/2, it is the most favorable for the emission of partial dislocations and easy to remove materials. The research content provides important references for the optimization of machining parameters and improvement of processing quality for the ultraprecision cutting of nickel-based alloy.