The effect of laser surface re-melting on the surface roughness and micro-hardness of selective laser melting (SLM) fabricated Ti-6Al-4V samples

Abstract

Ti-6Al-4V is favourable due to its exquisite properties for example, low modulus, light weight, excellent strength, and corrosion resistance. Despite the excellent properties of the material, the fabrication process of titanium components is challenging due to the poor final surface quality components caused by non-uniform powder distribution during additive manufacturing (AM) using selective laser melting (SLM) process. SLM process produces fully denser parts with better mechanical properties compared to the bulk materials, although the surface quality is poor. This work aims to study the effect of laser surface re-melting (LSM) on the hardness and surface properties of Ti-6Al-4V alloy. The fabricated Ti-6Al-4V sheet was re-melted by a 3 kW IPG Fiber laser. Microstructural evaluations of the Ti-6Al-4V sheet were characterized using an optical microscope. Micro-hardness and surface roughness measurements were determined by means of an HV Vickers tester under an applied load of 300g and load time of 10s and MarSurf PS1 roughness tester machine respectively. Microstructural evolution and hardness properties were all examined before and after the LSM treatment. The experimental results showed the formation of martensitic structure on the areas treated. Micro-hardness depth profiling results showed an average increase of 15–25% which was higher compared to the average hardness of the as-received. The results indicated that the roughness measurements lowered when both the residence time and irradiance increase. Laser surface re-melting treatment showed an improvement of the microstructural modifications and hardness properties therefore, the process can be used to modify the component’s surface for reliable and best surface finish.