Residual tensile stress mitigation and surface hardness enhancement in Ti6Al4V alloy via elevated temperature laser surface melting

Abstract

Laser surface melting (LSM) is a versatile technique used to modify surface properties without affecting the bulk characteristics of materials. This paper investigates the effects of LSM with pre-heating at different temperatures on the induced residual tensile stresses, hardness, and surface topography of Ti6Al4V alloy. A finite element-based numerical model is developed to analyse the cooling rate during the process. Cooling rates decrease, and melt pool dimensions increase in LSM at elevated temperatures. This decreases the residual tensile stresses and increases the microhardness. Experimental results reveal that higher pre-heating temperatures lead to up to 42 % reduction in residual tensile stress and up to 25 % improvement in microhardness, with minimal effect on surface topography. This study highlights the efficacy of elevated temperature LSM to mitigate residual tensile stresses and enhance surface hardness, which is promising for defence, aerospace, and automotive applications.