Surface morphology and defect characterization during high-power fiber laser cutting of SiC particles reinforced aluminum metal matrix composite

Due to the introduction of ceramic reinforcement, the physical properties and machinability of SiCp/Al composites are greatly different from the metallic ones. High-power continuous wave fiber laser makes it possible to process SiCp/Al composites with high efficiency. In this work, the feasibility of high-power fiber laser cutting of 5.0 mm thick SiCp/Al composites was studied using design of experiments (DOE). The effects of laser power (1000-4000 W), cutting speed (500-2000 mm/min) and assist gas (N-2 and O-2) on kerf geometry and defect characterization were investigated. Results showed that high laser power and low cutting speed generated relatively higher kerf width on the entry surface, and the kerf width exhibited a slightly higher level around similar to 2.0% when O-2 was applied in comparison to the results from N2 group. Different morphology was observed on machined surfaces including multi-directional striation, vertical striation and slant striation. The width of HAZ increased along the direction of laser beam, and reached the maximum value at egress with the value up to 1115 mu m. The SEM and EDX spectra study showed that the effect of oxygen on the subsurface was limited, and there was no metallurgical reaction between the matrix and SiC particles during laser cutting process.