Microstructural anisotropy and near-isotropic tribological behavior of electron beam powder bed fusion Ti–6Al–2Sn–4Zr–2Mo alloy

Abstract Ti–6Al–2Sn–4Zr–2Mo (Ti6242) is a near-α titanium alloy developed for high-temperature applications, yet its tribological behavior in additively manufactured conditions remains insufficiently understood. This study aimed to investigate the influence of build orientation on the microstructure and tribological performance of Ti6242 components produced via electron beam powder bed fusion (EB-PBF) across temperatures from room temperature to 450 °C. The outcomes revealed that a higher fraction of equiaxed grains was observed in the horizontally oriented samples compared to the vertically oriented ones, reflecting the influence of build orientation on the microstructural anisotropy. Abrasive wear emerged as the predominant mechanism in EB-PBF-Ti6242 and Al 2 O 3 ball interactions under all tested conditions. The tribological behavior at 450 °C exhibited characteristics comparable to those at room temperature, with a friction coefficient of approximately 0.5 and a wear volume about 10% lower than that measured at room temperature, may be attributed to the formation of a TiO 2 tribolayer. Although the horizontal sample possessed smaller porosities and slightly higher hardness than the vertical one, no significant wear anisotropy was observed under a 5 N load, due to the combined effects of microstructure, surface topography and local stress response. The similarity in tribological performance of Ti6242 alloy at different temperatures, regardless of build direction, underscores its uniform wear resistance across a wide range of operating conditions.

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