Experimental study on blue diode laser induced powder bed fusion of Ti-6Al-4V for improvement of energy efficiency

Ti-6Al-4V (Ti64) plate was additively fabricated with high energy efficiency by a blue diode laser induced powder bed fusion (L-PBF). Ti64 is widely used in many industrial fields, such as aerospace and medical fields, due to its excellent properties such as specific strength, heat resistance, and corrosion resistance. However, the shape of the fabrication is limited because Ti64 is a difficult-to-machine material. Therefore, L-PBF, which is one of the Additive Manufacturing (AM) technologies, has attracted attention to fabricate object freely. L-PBF is a method of fabricating 3D parts by repeatedly melting and solidifying metal powders with a laser. In L-PBF, near-infrared (NIR) fiber laser was generally used. It has been reported that the Volumetric Energy Density (VED) was 59 J/mm³ for fabricating Ti64 part. The light absorption rate of Ti64 increases with shorter wavelengths of the laser. The absorption rate at a wavelength of 450 nm is 1.3 times higher than that of 1 μm. Therefore, we developed a L-PBF machine equipped with a 200 W blue diode laser. Using the device, Ti64 part was formed with a porosity of 0.03 % at a VED of 41 J/mm³ under the condition of a laser output of 200 W, a scanning speed of 400 mm/s, and a spot diameter of 250 μm.