Influence of Surface Laser Treatment on Mechanical Properties and Residual Stresses of Titanium and its Alloys

Abstract

Surface modification of the titanium and its alloys used in implantology with a long-pulse laser can change the surface topography, but it also leads to changes in the stress sign and magnitude in the resulting subsurface layer. The presented research was aimed at evaluating the state of stress after laser remelting with the Nd:YAG laser of pre-etched titanium alloys Ti6Al4V and Ti13Nb13Zr and pure titanium. The obtained surface layers were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), optical profilography, and nanoindentation studies. Based on the results obtained after the nanoindentation tests, the character of the stresses generated in the melted layers was calculated and determined. Laser processing resulted in surface layer thicknesses between 191-320 µm and surface roughness Ra between 2.89-5.40 µm. Laser processing caused increasing hardness, and its highest value was observed for the titanium alloy Ti13Nb13Zr - 5.18 GPa. The tensile stresses appeared following laser treatment and increased with elevating laser power up to the highest value for titanium.

Keywords

• titanium
• mechanical properties
• roughness
• laser treatment
• residual stresses