Effect of machining parameters on heat-affected zone and kerf width in hybrid laser- waterjet process

One of the problems with laser machining is the heat-affected zone (HAZ) generated due to the intense heat applied to the workpiece. Moreover, in laser micromachining, the imprecise kerf width control reduces precision. A hybrid waterjet–laser (WJL) process without abrasive particles was used to counter these problems. In the hybrid WJL process, water pressure flushes out molten materials from the cut section, thus reducing the kerf width. Waterjet also enhances workpiece cooling compared to dry laser and results in reduced depth of HAZ. In this study, first a waterjet nozzle with a diameter of 0.4 mm was attached to a laser fiber machine featuring a constant wavelength of 1080 nm and power of 1500 W. Then, the interactions of cutting speed, laser power, focal length, and waterjet pressure on the HAZ and kerf width were investigated. CK75 high-carbon steel was used in this study. It was observed that increasing the cutting diameter leads to reduced HAZ depth and kerf width; whereas, increasing the power increases both said parameters. Furthermore, increasing waterjet pressure reduced HAZ depth and kerf width. The minimum HAZ depth and kerf width were obtained at a focal length of 3 mm., whereas the best HAZ depth and kerf width were 57 micrometers and 217 micrometers, respectively.