Improvement of Surface Mechanical and Tribological Characteristics of L-PBF Processed Commercially Pure Titanium through Ultrasonic Impact Treatment

• Published in: Acta metallurgica sinica : English letters 2024-06, Vol.37 (6), p.1034-1046
• Main Authors: Ansarian, Iman, Taghiabadi, Reza, Amini, Saeid, Mosallanejad, Mohammad Hossein, Iuliano, Luca, Saboori, Abdollah
• Format: Article
• Language: English
• Subjects: Acicular powders; Alloys; Characterization and Evaluation of Materials; Chemistry and Materials Science; Coefficient of friction; Corrosion and Coatings; Deformation; Investigations; Lasers; Manufacturing; Materials Science; Mechanical properties; Metallic Materials; Microstructure; Nanohardness; Nanoindentation; Nanotechnology; Organometallic Chemistry; Powder beds; Residual stress; Spectroscopy/Spectrometry; Styli; Topography; Transplants & implants; Tribology; Wear rate
• ISSN: 1006-7191; 2194-1289
• DOI: 10.1007/s40195-024-01696-y

Multi-pass ultrasonic impact treatment (UIT) was applied to modify the microstructure and improve the mechanical and tribological characteristics at the near-surface region of commercially pure Ti (CP-Ti) specimens produced by the laser powder bed fusion (L-PBF) method. UIT considerably refined the L-PBF process-related acicular martensites (α′-M) and produced a well-homogenized and dense surface microstructure, where the porosity content of 1-, 3-, and 5-pass UITed samples was reduced by 43, 60, and 67%, respectively. The UITed samples showed an enhancement in their near-surface mechanical properties up to a depth of about 300 μm. The nanoindentation results for the 3-pass UITed sample revealed an increase of about 53, 45, and 220% in its nanohardness, H / E r , and H 3 / E r 2 indices, respectively. The stylus profilometry results showed that performing the UIT removed the L-PBF-related features/defects and offered a smooth surface. The roughness average ( R a ) and the skewness ( R sk ) of the 3-pass UITed sample were found to be lower than those of the L-PBFed sample by 95 and 223%, respectively. Applying the UIT also enhanced the material ratio, where the maximum load-bearing capacity (~ 100%) in as-L-PBFed (as-built) and 3-pass UITed samples was obtained at 60- and 10-µm depths, respectively. The tribological investigations showed that applying the UIT resulted in a significant reduction of wear rate and average coefficient of friction (COF) of CP-Ti. For instance, under the normal pressures of 0.05 and 0.2 MPa, the wear rate and COF of the 3-pass UITed sample were lower than those of the L-PBFed sample by 65 and 58%, and 20 and 17%, respectively.