The Study Of Femtosecond Laser Processing On TiC Ceramic

By reason that femtosecond laser has advantages of wide material adaptability,non-contact, no mechanical shear stress, high precision, no pollution and highefficiency, femtosecond laser machining is one of the most ideal means ofmicro-machining.In this paper, femtosecond laser was used to process TiC ceramic. The effects oflaser fluence, repetition rate, scanning speed, number of turns, assisted gas pressureand feeding speed on TiC ceramic circular ring, circular surface and micro-holemachining were studied. Meanwhile, the interaction mechanism between femtosecondlaser and TiC ceramic was discussed by using EDS, Raman spectra and XPS.(1) The effects of parameters on TiC ceramic circular ring machining were studied,the results showed that: the width of circular ring increased along with laser fluence.When laser fluence was higher than0.76J/mm2, the width of circular ring would notincrease any more and would be stable at about30μm. Repetition rate had few effectson the width of circular ring, but deeper depth could be processed in circular ring byusing high repetition rate.(2) The effects of processing parameters on TiC ceramic circular surfacemachining were studied, the results showed that: when laser fluence was higher than0.51J/mm2, the diameter of circular surface would be stable. Repetition rate had feweffects on the diameter of circular surface. With increasing laser fluence and repetitionrate, the processing effect was more noticeable in depth direction, blind holes could beobtained. With the increase of number of turns and processing time, the flatness ofcircular surface turned out to be better and the circular surface could be processedmore fully, meanwhile, the processing efficiency would decrease. Thus, an overallconsideration should be taken when choosing the number of turns. (3) The effects of processing parameters on TiC ceramic micro-hole machiningwere studied, the results showed that: the circularities of micro-holes on the entry sidewere not less than99%when laser fluence varied. The circularity of micro-holes on theexit side increased along with laser fluence., it tended to be stable when laser fluencewas higher than0.76J/mm2. The taper of micro-holes increased along with assisted gaspressure. When laser fluence was0.51J/mm2, the taper of micro-holes drilled with3bar assisted gas pressure was the best: its long axis taper was-0.13°and short axistaper was0.77°. The diameters of entry side and exit side of micro holes were alldecreasing while the feeding speed was increasing. The taper of micro-holes drilledwith6.4μm/s feeding speed was the best: its long axis taper was-0.47°and short axistaper was-0.14°. A set of good parameters in processing micro-holes on TiC ceramicwere: laser fluence0.76J/mm2, repetition rate100kHz, assisted gas pressure3bar,feeding speed6.4μm/s.(4) The interaction mechanism between femtosecond laser and TiC ceramic wasstudied, the results showed that: the stripe shape cycle structure, the melt deposit layer,small ball, cauliflower shape oxide were four typical characteristics formed duringlaser processing TiC ceramic circular ring. Ti-C bonds ruptured through multiphotonabsorption of TiC ceramic which was irradiated by femtosecond laser. The surpluscarbon and the carbon ionized from TiC interacted with oxygen in air to generate gasand evoluted；part of Ti ions interacted with the oxygen in air to form Ti2O3and TiO2,and other Ti ions existed in the form of metal Ti in the melt and residue.