Femtosecond Laser Machining Of Axisymmetric Microstructured Surfaces

Silicon carbide(SiC), as one of the multi-phase ceramic materials, exhibits theoutstanding advantages like high hardness, wear resistant, heat resistant and goodchemical stability. The inherent excellent precision stability and the extended lifeexpectancy of SiC make it the attractive candidate material for applications of makingmicro-structure molds.Due to its high hardness and brittleness, SiC is a typical materialwhich is difficult to process. Ultra-precision grinding technology, as one of the mostreliable processing methods for superhard material, has some defects such as quickabrasion of grinding wheels and low processing efficiency in the machining of SiC. Tosolve the above mentioned problem, the femtosecond laser machining technology wasintroduced for SiC material in this paper.In this paper，according to the application requirements of the four-axis precisionworking platform and the inherent defects of the control software used in thefemtosecond laser machining, the modular design philosophy was adopted to developsecondly the control software of the stage in the VC++environment.The software isuser-friendly and easy to operate, which enhancs the motion performance of the stage,and ensures the accuracy and repeatability of microstructure machining.The effect of plasma that causes laser beam defocused on the hole quality wasstudied by the experiments tested on holes drilled by femtosecond laser in air, nitrogen,argon and helium mediums. The variations of the ablation threshold of SiC in differentgas mediums were discussed. The above experimental results show that the best holequality was obtained in the helium medium, wherein the ablation threshold of SiC waslimited to only0.2340J/cm2. In comparison, the helium was selected as the soundtransmission medium for femtosecond laser machining of microstructure surface.The effect of laser power, scan speed and gas flow rate on silicon carbide ablatedby femtosecond laser was also investigated. The appropriate processing parameterswere selected to fabricate the axisymmetric microstructure. In addition, the surfacemorphology, dimensional accuracy and thermal damage on the subsurface of themicrostructure were detected. The results show that the obtained microstructureexhibited a good surface morphology and high dimensional accuracy and the surfaceoxidation phenomenon almost disappeared. However, there existed some thermaldamage on the subsurface of the microstructure.