Temperature Monitoring of Ti-6Al-4V Alloy in Laser Surface Smoothing with Near-Infrared Spectroscopy and Its Influence on Surface Roughness

Abstract Laser Surface Smoothing (LSS) is a widely used technique for improving the surface quality of materials, particularly in additive manufacturing (AM), where high surface roughness and porosity are prevalent. Despite the benefits of LSS, the technique faces challenges due to the fluctuation of input parameters, such as laser power and scanning speed, leading to inadequate surface smoothening. Hence, this study ultilised the processing temperature which has been determined via near-infrared spectroscopic method as a monitoring parameter for LSS. The LSS of Ti-6Al-4V alloy was carried out with a continuous-wave ytterbium fiber laser with various power in the range of 120 to 540 W. The near-infrared spectroscopic system captured the thermal radiation spectra emitted during the LSS. The processing temperatures were extracted from each spectra using Planck’s law fitting. Thus, the optimum processing temperature for an efficient LSS of Ti-6Al-4V alloy was determined to be 2060 K. The study observed a consistent processing temperature throughout each laser power input during the LSS. A direct relationship between laser power and processing temperature was established. These findings can lead to the development of a reliable monitoring method for LSS, ensuring stability and consistency in the technique, and contributing to the literature on LSS for the Ti-6Al-4V alloy.