Study on chip morphology and milling characteristics of laser cladding layer

Abstract

Laser cladding, which can increase the hardness and wear resistance of the used components, is widely used in remanufacture and sustainable manufacturing field. Generally, laser cladding layer should be machined to meet the function as well as the assembly requirements. Milling is an effective means for precision machining. However, there exist great differences of physical and mechanical performances between laser cladding layer and substrate material, such as microstructure, hardness, mechanical properties, etc. This produces some new milling problems for laser cladding layer. An insightful understanding of milling mechanism of laser cladding layer is inevitable. There still lacks the research on this subject, such as chip morphology and mechanical behavior, vibration during laser cladding layer milling process, etc. Thus, the change of chip morphology depending on the cutting parameters and microhardness variation was studied. Signal analysis methods of time and frequency domains of cutting forces and machining vibration were used to evaluate the milling characteristics of laser cladding layer. The microstructural analysis indicates that shear-induced lamella structures are the basic features for the chip free surface. The height-to-thickness ratio of saw-tooth chips increases with increasing cutting speeds and feeds. Microhardness profiles on the top surfaces of machined chip decrease from the back surface to the bulk chip, and the shear band shows increased hardness. The cutting force and machining vibration acceleration of laser cladding layer are higher than those of the KMN steel substrate at the same cutting parameters. The machining vibration is characterized by high vibration in the intermediate position of each layer and low vibration in the joint surfaces between layers.