Effect of built orientation on direct metal laser sintering of Ti-6Al-4V

Abstract

The use of direct metal laser sintering for fabrication of three-dimensional engineering parts is fast gaining momentum in the engineering industries. This process consolidates metallic powders by using a laser source. In this study, the effect of built direction (horizontal and vertical) on the microstructure, mechanical properties and corrosion resistance of Ti-6Al-4V alloy printed using direct metal laser sintering (DMLS) technology was investigated. Results show that microstructure of Ti-6Al-4V surface have few pores. The melt pool of vertically built parts revealed the presence of fine cellular-dendritic martensite. Microhardness of vertical built specimens was relatively higher than the horizontal built specimens which could be due to the presence of vanadium carbide. Fractography analysis revealed that horizontal built specimens displayed higher ductility than the vertical built. For horizontal built sample, the corrosion current densities in 3.5% NaCl and 1 M HCl solutions are significantly lower when compared with that of 1 M H₂SO₄, which might be because of stable oxide layer formation. Generally, horizontal build parts yield relatively better mechanical properties and corrosion resistance supported by ideal microstructure. In case of vertical built-up, it is better to limit to a maximum height of 40 mm for the set parameters.