Acta Metallurgica Sinica (English Letters) ›› 2024, Vol. 37 ›› Issue (6): 1034-1046.DOI: 10.1007/s40195-024-01696-y

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

Iman Ansarian1, Reza Taghiabadi1(), Saeid Amini2, Mohammad Hossein Mosallanejad3, Luca Iuliano3, Abdollah Saboori3   

  1. 1Department of Materials Science and Metallurgy, Imam Khomeini International University (IKIU), Qazvin, Iran
    2Department of Mechanical Engineering, University of Kashan, Kashan, Iran
    3Integrated Additive Manufacturing Center, Department of Management and Production Engineering, Politecnico di Torino, Corso Duca Degli Abruzzi 24, 10129 Turin, Italy
  • Received:2023-11-07 Revised:2024-01-06 Accepted:2024-01-21 Online:2024-06-10 Published:2024-04-09
  • Contact: Reza Taghiabadi, taghiabadi@ikiu.ac.ir

Abstract:

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/Er, and H3/Er2 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 (Ra) and the skewness (Rsk) 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.

Key words: Laser powder bed fusion, Ultrasonic impact treatment, Commercially pure Ti (CP-Ti), Surface mechanical properties, Tribological properties