Reaction-bonded silicon carbide (RB-SiC) is a typically hard and brittle material that is prone to a large number of machining defects in conventional processing. In this study, laser in-situ assisted diamond cutting (In-situ LAC) technique was proposed to reduce the machining defects of RB-SiC in order to achieve a mirror machined surface. Firstly, a nano-indentation study of SiC, Si phase and position at the phase boundary under a constant load of 100 mN and 300 mN was carried out. The measured hardness value data and the indentation morphology observed by scanning electron microscopy (SEM) were used to investigate the weak position of RB-SiC and analyze the causes of the defects deeply. Then In-situ LAC and ordinary cutting (OC) of RB-SiC experiments were carried out to compare the machined surface quality. The SEM analysis of the machined surface features was also used to point out the suppression effect of the machined surface defects by the laser. It was found that brittle fractures on the surface of SiC particles were suppressed, leading to a significant increase in the ductile processing regions of SiC and Si. To further investigate the effect and mechanism of laser on the suppression of subsurface defects in processing. The surface was cut by focused ion beam (FIB) and the cross-sectional morphology was observed in-situ. The extension of subsurface cracks and fracture defects were further analyzed to explore the defect suppression mechanism more comprehensively.
Fused silica has been widely used in precision instruments in extreme environment for its excellent properties such as high temperature resistance and thermal shock resistance. However, the brittleness and hardness nature of fused silica makes it difficult to achieve high quality surface through conventional technology. In recent years, the laser in-situ assisted machining has been proposed as a promising technique for ultra-precision machining of many brittle and hard materials. In this study, numerical simulations and cutting experiments were conducted to study the temperature field and cutting mechanism in laser in-situ assisted machining of fused silica. The cutting temperature and machined surface quality under different machine parameters were characterized. The results indicate that the assistance of laser improves the material’s ductile machinability significantly, which contributes to a higher surface quality compared to conventional machining. The depth of cut (DOC), laser power and rotation speed have a great impact on the surface quality, and surface roughness values in the order of 20 nm can be achieved under appropriate machine parameters.
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