High-speed airflow provides a certain cooling effect on the laser-ceramic interaction zone, reducing the heat conduction depth of the laser-ceramic interaction into the matrix. This results in a decrease in the thickness of the recast layer caused by rapid cooling after melting. When the cutting speed increases to a certain value, the pulse superposition decreases, the thermal interaction time per unit length decreases, and matrix fracture may even be partially facilitated by thermal vibration. During the pulse pause, the laser nozzle travels a distance exceeding the spot diameter, the pulse laser superposition effect disappears, and when a single pulse acts alone, its temperature gradient is large and the heat conduction time is short, making the cooling effect of the high-speed airflow insignificant.
Under the premise of a pulse width of 0.3 ms and a supersonic cutting airflow with combined action, average power is the most important factor affecting the thickness of the recast layer, followed by cutting speed, and then pulse frequency. Average power is a key factor determining the peak energy of a single pulse, which in turn is a key factor determining the temperature gradient, i.e., the depth of heat conduction. Increasing the pulse frequency can improve the pulse overlap, but it does not necessarily lead to heat accumulation or an increase in the equivalent amount of heat conduction to both sides of the cut. Increasing the cutting speed essentially reduces the heat accumulation caused by pulse overlap until the thickness of ceramic that a single pulse can cut is reached. Therefore, selecting an appropriate average power, coupled with matching the cutting speed and pulse frequency, is a prerequisite for obtaining a smaller recast layer thickness.
