Research on Surface Integrity Evolution of Short Arc Assisted Milling of Superalloy
Short arc milling technology is applied to nickel-based superalloy processing due to low machining stress,low cost and high machining efficiency.Aiming at the problem that the evolution law of surface integrity in short arc assisted precision milling is unclear,the microstructure characteristics of the recast layer are analyzed by means of scanning electron microscope(SEM),energy dispersive spectrometer(EDS)and other detection methods.The influence of precision milling process parameters on surface integrity and the difference of milling surface caused by the presence of recast layer are studied by orthogonal milling experiments.The surface strengthening mechanism of short arc assisted precision milling is clarified.The results show that the destruction and recombination of the superalloy crystal at high temperature leads to its microstructure change to form a recast layer,the hardness is reduced by 34％,and the brittleness is enhanced.Under the same parameters,the surface of short arc assisted milling shows higher roughness(Ra=0.76μm),higher surface hardening rate(47.8％),and larger tensile residual stress(along the feed direction(X direction)is 241.5 MPa,and in the vertical feed direction(Y direction)is 78 MPa).Dislocation strengthening is the main mechanism of machined surface hardening.The microhardness prediction model established by introducing the kernel average misorientation parameter further expands the relationship between surface integrity and crystallographic characteristics.
short arcrecast layerssurface integritymicrohardnesssurface strengthening
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