Laser Shock Peening of Orthopaedic Ti-6Al-7Nb: Evaluation of Topography, Wetting Characteristics, Microstructure and Residual Stress
X. Shen, P. Shukla, F. Yao, S. Nath, Z. An and J. Lawrence
This paper is focused on a study of wetting characteristics post laser peening (LSP) of orthopaedic titanium alloy (Ti-6Al-7Nb) for the -time. A 10J, 8ns, 1064nm wavelength, Nd:YAG Laser was employed. Residual stress was measured using the incremental hole drilling method. Residual stress results showed maximum compressive stress of -420 MPa, and -100 MPa at a depth of 0.8mm. The surface roughness was increased from 0.15 μm to 0.87 μm after multiple LSP impacts. The contact angle measurements were undertaken by using a sessile drop device with water and ethylene glycol. Both liquids showed that LSP increase the contact angle by 17% and 30.4% respectively using water and ethylene glycol. In addition, further verification was made using the Fowkes model to calculate the surface energy. This yielded the total energy, diversion and polar component to have reduced. The increased contact angle of LSPned samples were affected by combination of increased surface roughness and decreased surface energy. The findings in this study not only form a base for further research, but also reveal the possibility of strengthening titanium implants and rendering them to become more biocompatible.
Keywords: LSP, wettability, contact angle, Ti-674-Nb, residual stress, SEM, 3-D profiling