Study on the influence of processing variables under various tilting angles of laser nozzle and substrate on the deposition quality of the multi-axis laser metal deposition

Abstract

This study developed a deposition guideline that considered the effect of processing variables, such as laser power, on the deposition quality at various tilting angles of laser nozzle and substrate when fabricating components of complex geometries like overhang and curved structures with the multi-axis laser metal deposition process. The guideline was based on analyzing the effect of processing variables, namely, laser power, beam diameter, and specific energy, on the deposition quality under six spatial variables. Spatial variables were defined by combining the angle of the substrate to the ground (0°, 45°, and 90°) with the angle of the laser nozzle to the substrate (90° and 45°). The bead contact angle and dilution were used as indexes of the deposition quality evaluation. If both the ideal ranges of the evaluation indexes are satisfied, the deposited material can exhibit high surface quality and geometrical accuracy. To prevent excessive dilution caused by the widened and flattened deposit under tilted laser nozzle conditions, a larger beam diameter, when compared to the state where the laser nozzle is perpendicular to the substrate, should be used. For a situation where the effect of the gravitational force is dominant, such as the substrate perpendicular to the ground, the laser power and the specific energy should be controlled simultaneously to maintain the ideal contact angle and dilution. In addition, the effect due to the change in the amount of melted powder on the cross-section geometry caused by beam diameter variation should be considered for every tilted motion.