Enhanced oxidation resistance of a titanium–based alloy by the addition of boron and the application of electron beam melting

•TiB precipitates were significantly refined in the EB-PBF-built Ti-6242S-1.0B alloy compared with forged alloys.•Finer oxides contributed to the formation of more compact oxidation layers in the EB-PBF-built alloy than as-forged alloy.•Evaporation of B2O3 from coarse TiB particles destabilized the oxidation layer in the as-forged alloy.•Evaporation of B2O3 from fine TiB particles did not destabilize the oxidation layer in the EB-PBF-built alloy.•EB-PBF-built Ti-6242S-1.0B alloy was more resistant to oxidation than the as-forged alloy. Refined TiB precipitates significantly enhance the oxidation resistance of Ti-6Al-2Sn-4Zr-2Mo-0.1Si-1.0B alloy fabricated by electron beam powder bed fusion (EB-PBF). Refined TiB precipitates in the EB-PBF-built alloy enable finer oxide formation than the larger precipitates in the forged alloy, and the resulting oxidation layers are more compact. Evaporation of scattered B2O3 generated by the refined TiB precipitates in the EB-PBF-built alloy do not significantly accelerate detachment of the oxidation layer from the substrate. However, collective evaporation of B2O3 generated by larger TiB precipitates in the forged alloy accelerate detachment. The oxidation layer on the EB-PBF-fabricated alloy was more stable, preventing further oxidation and improving oxidation resistance.