Effects of Laser Repetition Rate and Fluence on Micromachining of TiC Ceramic

Micromachining of titanium carbide (TiC) ceramic is very difficult because of its high hardness and brittleness. Femtosecond pulsed laser was employed to process circular rings on the surface of TiC ceramic. The interaction area between femtosecond laser pulses and TiC at different laser repetition rates and fluences was studied. Morphology and composition of irradiated area were analyzed by scanning electron microscope, energy dispersive spectroscopy, and Raman spectrum. The results indicated that the radius of outer circle was close to the intended radius. Laser fluence had obvious effects on the radius and width of circular rings, compared to laser repetition rate. The width of circular rings increased rapidly with increasing laser fluence from 2.55x10(-2) to 1.27x10(-1)J/mm(2), and then stabilized at around 40 mu m when laser fluence was above 7.64x10(-1)J/mm(2). The surface of circular rings was characterized by ripples at the lower laser fluence. With increasing laser fluence, four kinds of typical morphology were observed, including ripples, cauliflower-like particles, ball-like particles, and deposited oxide layer. Ball-like particles contained high concentration of titanium, which came from melt ball splashing from ablation area. The others came from the different oxidation stages occurred on the surface of TiC sample.