The present study reveals for the first time the dry sliding wear behavior of a powder metallurgical pure titanium alloy (Cp-Ti) modified by shot peening. Cp-Ti samples were manufactured via powder metallurgy, and then their surface and subsurface features were modified using a custom-made, fully automated shot-peening system. The texture isotropy rate and the highest orientation angle of the shot-peened samples were 71.5% and 36°, respectively. The Abbott curves of the shot-peened surfaces revealed that the most common areal roughness value was 5.177 μm, with a frequency of 8.1%. Shot-peened surfaces exhibited an ~20% lower wear rate than unpeened surfaces under dry sliding wear, whereas the coefficient of friction was the same for both surfaces. Micro-ploughing, micro-cutting, oxidation, and three-body abrasion wear mechanisms were observed on the shot-peened and unpeened surfaces. High resolution 3D surface topographies of worn unpeened and shot-peened surfaces revealed micro-scratches and inhomogeneities along wear tracks, which are indicative of three-body abrasion mechanisms during contact. In addition, vertical and horizontal microcracks were visible just beneath the wear track, suggesting a clear indication of plastic deformation during contact. The cross-sectional hardness maps of shot-peened samples revealed the formation of a work-hardened surface layer with shot peening, which improved the wear resistance. These findings support that shot peening can be a useful tool to modify the surface and tribological properties of powder metallurgical Cp-Ti alloys.

For the first time, the present study investigates the corrosion, surface, and subsurface properties of a shot-peened Ti6Al4V powder metallurgical alloy produced via pressure-assisted sintering. Shot peening yielded a fine-grained microstructure beneath the surface down to 100 microns, showing that it caused severe plastic deformation. XRD analysis revealed that the sizes of the crystallites in unpeened and shot-peened Ti6Al4V alloy samples were 48.59 nm and 27.26 nm, respectively, indicating a substantial reduction in crystallite size with shot peening. Cross-sectional hardness maps of shot-peened samples showed a work-hardened surface layer, indicating a ~17% increase in near-surface hardness relative to unpeened samples. Three-dimensional surface topographies showed that shot peening yielded uniform peaks and valleys, with a maximum peak height of 4.83 μm and depth of 6.56 μm. With shot peening, the corrosion potential shifted from −0.386 V to −0.175 V, showing that the passive layer developed faster and was more stable than the unpeened sample, improving corrosion resistance. As determined via XRD analysis, the increased grain refinement (i.e., the number of grain boundaries) and the subsequent accumulation of TiO₂ and Al₅Ti₃V₂ compounds through shot peening also suggested the effective formation of a protective passive layer. As demonstrated via electrochemical impedance spectroscopy, the formation of this passive film improved the corrosion resistance of the alloy. The findings will likely advance surface engineering and corrosion research, enabling safer and more productive shot peening in corrosion-critical applications.

The present study investigates the microstructural, mechanical, and tribological properties of Inconel 718 alloy produced by selective laser melting (SLM) in relation to heat treatment. The SLM-processed samples received a two-step heat treatment: solutionizing at 1065 °C for 1 h, followed by double aging at 720 °C for 8 h and 620 °C for 6 h. The as-built sample exhibited a grain structure mostly characterized by fine Laves phases, while the hardening phases γ′ ((Ni₃ (Al, Ti)) and γ″ (Ni₃Nb) precipitated during the heat treatment. Following heat treatment, a transformation in crystallographic texture and dislocation density occurred, yielding a random texture and reduced dislocation density, particularly in the XZ direction, attributed to the formation of new grains via recrystallization in the microstructure. The grain size in the XY plane decreased following heat treatment, whereas the texture in the direction remained unaffected. The heat-treated samples had significantly higher tensile strength (1330 MPa vs. 960 MPa) and hardness (530 HV vs. 340 HV) relative to the as-built samples. The wear resistance of heat-treated samples surpassed that of the as-built sample due to enhanced mechanical properties resulting from the fine and dispersed γ′ and γ″ precipitates in the microstructure with heat treatment.

Interest in textured surfaces for biomaterials and implants is increasing, with shot peening emerging as a promising method for surface modification. This study investigates the influence of conventional and fine shot peening on the surface morphology, topography, wettability, and antibacterial properties of biomedical-grade Ti6Al4V alloy. Peening was conducted using a custom-built, fully automated system, employing fine (100–200 µm) and coarse (700–1000 µm) shots using well-controlled sets of parameters. Both treatments introduced severe plastic deformation on the surface, resulting in increased roughness. Conventionally shot-peened samples exhibited deeper and wider dimples compared to finely peened ones. Surface wettability shifted from hydrophilic (contact angle: ~4°, untreated) to hydrophobic, reaching contact angles of ~91° and ~100° for fine and conventional shot peening, respectively. Antibacterial assays against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) were evaluated by normalizing colony counts to the untreated Ti6Al4V surface. The inherent antibacterial response of Ti6Al4V against E. coli was preserved after both shot peening treatments, showing no notable increase in bacterial proliferation. In contrast, adhesion of S. aureus increased, more notably on fine shot-peened surfaces, indicating a strain-specific response influenced by surface roughness and wettability. In summary, both fine and conventional shot peening altered the surface morphology, topography, and wettability of Ti6Al4V. At the same time, their antibacterial influence was strain-dependent, underscoring the need for careful parameter selection in biomedical applications.