Effect of boron addition on microstructure, hardness and wear performance of Ti-6Al-4 V alloy manufactured by laser powder bed fusion additive manufacturing

In the present work, the effect of the addition of elemental boron in Ti-6Al-4V alloy powder for in-situ fabrication of TiB/Ti-6Al-4V nanocomposites using laser powder bed fusion (L-PBF) technique with commercial processing parameter of EOSINT 280 machine was studied. The microstructural evolution with varying boron addition was examined using an optical microscope (OM), field emission scanning electron microscope (FESEM), and electron backscatter diffraction (EBSD). The added boron (0.1–1.5 wt%) reacted completely with Ti to form needle-like nano/micro TiB particles and induced grain refinement in the microstructure. The L-PBF fabricated TiB/Ti-6Al-4V composites with 0.5 wt% B and above altered the microstructure drastically from martensitic lath to equiaxed α. The microhardness and wear properties of the nanocomposite improved significantly with the increased concentration of boron. Nearly four-fold improvement in wear performance was associated with grain refinement and the formation of nano-sized TiB precipitates.