Effect of Laser Surface Melting Process Parameters on the Melt Pool, Microstructural Evolution, and High-Temperature Oxidation Study of Ti6Al4V Alloy Fabricated by Laser Powder Bed Fusion

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Abstract
This study investigates the effect of laser surface melting (LSM) process parameters on melt pool characteristics, microstructural evolution, and the high-temperature oxidation behavior of Ti6Al4V alloy specimens fabricated via laser powder bed fusion (LPBF). Ti6Al4V samples measuring 25 × 25 × 4 mm were fabricated by LPBF and then subjected to LSM with varying laser powers (400, 600, 800 W) and scanning speeds (300, 600, 900 mm/min). Results indicate that surface roughness decreased from 14.6 to 11.8 μm (a reduction of 19.18%) after LSM for 400 W and 900 mm/min conditions, due to the removal of powder particle adhesion and surface cracks. At higher laser power (800 W) and laser scan speeds of 300, 600, and 900 mm/min, a keyhole melt pool was formed with penetration depths of 1.90, 1.61, and 1.16 mm, respectively, which are known for good strength and ductility. The LSM zone exhibited 99.4% refined α’ martensite with a dendritic microstructure and a reduced β-phase content of 0.6%, attributable to rapid cooling rates. Microhardness increased significantly from 382 ± 13 to 614 ± 16 HV (increased up to 60.7%) due to the fine martensitic with dendritic structure. The oxidation analysis showed that as-deposited (AD) samples exhibited greater weight gain due to increased oxygen exposure, whereas LSM regions showed reduced weight gain because an Al-rich layer inhibited oxygen diffusion.

[Other] Effect of Laser Surface Melting Process Parameters on the Melt Pool, Microstructural Evolution, and High-Temperature Oxidation Study of Ti6Al4V Alloy Fabricated by Laser Powder Bed Fusion

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[Other] Effect of Laser Surface Melting Process Parameters on the Melt Pool, Microstructural Evolution, and High-Temperature Oxidation Study of Ti6Al4V Alloy Fabricated by Laser Powder Bed Fusion Copy

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[Other] Effect of Laser Surface Melting Process Parameters on the Melt Pool, Microstructural Evolution, and High-Temperature Oxidation Study of Ti6Al4V Alloy Fabricated by Laser Powder Bed Fusion