Tribological Response of Laser Powder Bed Fusion-Fabricated Ti–6Al–4V Alloy: Role of Microstructure, Mechanical Properties, and Scanning Speed

Abstract The tribological behavior of Ti–6Al–4V alloy fabricated via laser powder bed fusion (LPBF) is highly sensitive to process parameters, particularly scanning speed, which significantly influences microstructure evolution, mechanical properties, and wear performance. This study examines how different scanning speeds influence microstructural features—such as acicular martensitic α′ phases, grain refinement, and residual stresses—and their impact on tribological performance. Intermediate speeds (600–700 mm/s) led to fine, uniformly spaced α′ phases and minimal defects, resulting in reduced internal strain and smaller grain sizes (5.97 ± 0.09 µm). These features enhanced dislocation pinning and thermal stability, improving microhardness and wear resistance. At 700 mm/s, hardness increased by ∼6% (from 380.2 ± 1.3 HV at 500 mm/s to 403.8 HV ± 2.0) and wear loss decreased by ∼19% (from 5389.6 mm3 at 500 mm/s to 4384.4 mm3), while the coefficient of friction profile was more stable, consistent with reduced porosity (0.23 ± 0.11%). In contrast, extreme scanning speeds (500 and 800 mm/s) resulted in coarser structures and higher porosity, which diminished overall performance.