Investigating double-scan strategies for reducing heat-affected zone in laser surface melting

Laser surface melting (LSM) is a technique for modifying surface topography without adding or removing material. LSM may result in large heat-affected zones (HAZs) that may be undesirable in several applications. The current work aims to investigate double-scan strategies to reduce HAZ. This strategy used two laser scans, each at half the line energy density used for a single scan. A numerical model is developed for LSM to predict the MZ and HAZ and is validated against experimental results using Ti6Al4V. In addition, the effect of the double-scan strategy on the surface roughness, hardness and residual stresses is evaluated. The experimental results show the HAZ depth decreased by 26%, the surface hardness was improved, and the resultant residual stresses were preserved for the double scan strategy compared to the single scan. However, it resulted in a relatively rougher surface finish.