Effect of low-power nanosecond fiber laser nozzle position on surface quality of inclined Ti-6Al-4V alloy plate

In this study, a detailed comparison between flat and inclined Ti-6Al-4V alloy plates under nanosecond fiber laser machining is presented, focusing on the combined effects of laser parameters and surface inclination on machining outcomes. The results demonstrate a strong interaction between laser power, beam inclination, and workpiece angle, significantly influencing the width, depth, and heat-affected zone (HAZ) of the machined surfaces. The width of the laser-treated region is highly sensitive to average laser power, exhibiting the greatest impact at the focal position (84.63%) and a similarly substantial effect near the nozzle (+15 mm defocus, 73.92%), while beam angle also contributes to width variations, though to a lesser extent. Groove depth is primarily governed by average power at focus (77.85%), with its influence decreasing at off-focus positions (−15 mm, 30.06%), whereas beam angle plays a more prominent role at defocused positions (42.76% at −15 mm). The HAZ is affected by both average power (64.65% at focus and 61.50% at −15 mm) and beam angle (7.42% at focus and 5.44% at −15 mm). Inclinations of 10° or higher result in increased spatter formation and a higher likelihood of micro-fracture, particularly at focal and +15 mm positions. This work highlights the importance of prioritizing width in laser machining, while depth can be adjusted according to other response requirements. The findings provide valuable insights for optimizing laser parameters to achieve superior surface quality in precision-critical industries such as aerospace, automotive, and medical device manufacturing.