Laser powder bed fusion of Ti6Al4V using low-cost high efficiency 450 nm diode point melting

Abstract

Laser Powder Bed Fusion (LPBF) is a commonly used Additive Manufacturing (AM) method for the production of geometrically complex metal components that are used in high-value sectors. It uses high power fibre lasers directed by a galvanometric scanner to rapidly melt powdered feedstock. LPBF systems are expensive, making them inaccessible to many sectors and have challenges related to in-process thermal control, production of large components and scalability limitations. As an alternative to traditional LPBF, this study introduces Diode Point Melting (DPM), combining multiple low-power, energy efficient blue (450 nm) diode lasers into a single focal point. DPM's laser source is fixed to a scanning gantry axis that traverses across the powder bed, creating a low-cost alternative to traditional LPBF (∼x10 lower laser hardware cost). DPM processes slower than LPBF, generating reduced thermal gradients with improved material laser energy absorption due to use of a shorter laser wavelength. DPM processing of Ti6Al4V was undertaken using 38W creating samples that were 99.41% dense. DPM's slower melt pool solidification rate enabled the formation of a stable α + β phase creating harder samples. The grain size of Ti6Al4V samples fabricated using DPM were significantly larger compared to those produced by LPBF (grain size area ∼ x30 larger). Young's modulus of the samples produced via DPM was found to be higher than LPBF manufactured Ti6Al4V, indicating increased stiffness. DPM is a promising low-cost alternative to LPBF, offering the opportunity to make net-shape metal AM more widely accessible in both academic and industrial sectors.

Keywords

• Additive manufacturing
• Laser powder bed fusion
• Ti6Al4V
• Diode point melting (DPM)
• Process optimization
• Microstructure