A new method for laser grooving titanium alloy with the assist of a hybrid of gas jet and waterjet

High efficiency and low thermal damage grooving with a good surface quality is critical for the positioning and assembly of titanium alloy parts, which are widely used in aviation manufacturing and shipbuilding industry. In this paper, a new method of laser grooving by the assist of a hybrid of gas jet and waterjet was proposed, and Ti6Al4V titanium alloy was used as the specimen. The gas jet was applied co-axially to the laser, while the waterjet was applied off-axially. The effects of relative direction between the waterjet and laser traverse, the gas/water pressure, and the waterjet nozzle diameter on the groove characteristics and heat-affected zone were investigated. The surface macro morphology and microstructure were also examined, as well as the compositional change. Results show that larger grooves with a better quality can be fabricated and the range of heat-affected zone is still limited below 100 µm, when compared with other laser grooving methods. In addition, reverse-grooving creates a deeper and cleaner groove than the other two directions used in this study. The largest groove size can be obtained when the water pressure, gas pressure and nozzle diameter are 10 MPa, 0.1 MPa, and 0.4 mm, respectively. Moreover, the metallographic photo and spectrogram obtained by scanning electron microscope (SEM) indicate that fine acicular martensite and titanium oxidation can be formed near the groove. This work provides a new approach for improving the waterjet assisted laser processing quality and helps understand its mechanism.