Material Removal Mechanism and Evaluation of Machined Surface Quality of SiCf/SiC Composites by Laser Ablation-assisted Milling
The high temperature resistance,high strength and light weight of SiCf/SiC composites are required for modern aerospace components,and SiCf/SiC composites have excellent comprehensive performance,but their high brittleness and anisotropy make it a challenge for high-performance manufacturing.Through the laser ablation pre-test,the physical phase composition and ablation mechanism of laser ablation products of SiCf/SiC composites are grasped,and the influence of laser parameters on the ablation properties is investigated.Through the comparison experiments of conventional milling and laser ablation-assisted milling,the material removal mechanisms of three different processing strategies,namely,conventional milling,partial ablation-milling and complete ablation-milling,are analysed,and the influence of the ablation layer ratio on the processing surface quality is investigated.It is shown that the laser ablation products are mainly composed of 3C-SiC and amorphous SiO2.In conventional milling,macroscopic brittle fracture of fibres occurred,and machining defects such as multiple cracks and pits existed on the machined surface.In partial ablation-milling,fibre fracture is dominated by microscopic brittle fracture,and fibre pull-out and macroscopic brittle fracture occurred at a few locations.In the full ablation-milling process,microscopic brittle fracture of fibres occurred,and scale fracture of the matrix occurred.The quality of laser ablation-assisted milling machining is superior to conventional milling,and the surface roughness was essentially the same for partial ablation-milling and complete ablation-milling.The difference in cutting force between milling with low and high ablative layer percentage is small.Micro-macro brittle fracture dominated the fibres in the milling process with low ablative layer percentage;micro-brittle fracture occurred in most of the fibres in the milling process with high ablative layer percentage.In summary,partial ablation-milling and low ablative layer ratio are the preferred processing solutions.
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