Serrated chips morphology and formation mechanism of laser additive manufactured materials for subtractive machining

The high-speed cutting process often results in the formation of periodic serrated chips, which can lead to fluctuations in cutting force. These fluctuations can negatively affect machining accuracy, surface roughness, and tool life. Moreover, the heterogeneous characteristics of laser additive manufactured (AM-ed) materials significantly influences chip morphology. Therefore, this study investigated the evolution mechanism of chip morphology in two types of Fe/Ni-based laser cladding layers, focusing on the effects of cutting speed. Geometric characterization, physical characterization, and deformation analysis of serrated chips were used to explore this mechanism. A four-stage composite formation model based on adiabatic shear-ductile fracture was proposed, and the effect of heterogeneous characteristics of laser AM-ed materials on chip formation was thoroughly discussed. The results show that as the cutting speed increases, the chip deformation of laser AM-ed materials intensifies, the chip morphology transitions from continuous strip chips to deformation band-type serrated chips, and eventually evolving into transition band-type serrated chips. The heterogeneous characteristics of the laser AM-ed materials promote the formation of adiabatic shear bands (ASBs) and the propagation of cracks, thereby increasing both the frequency of ASBs and the uncertainty of crack propagation directions. This leads to irregular chip geometry and non-periodic features in the serrated chips. In addition, the wear resistance of the machined surface of Fe/Ni-based laser AM-ed materials is excellent, which has a positive impact on improving the surface properties and service life of the mechanical parts.