Laser surface treatment to improve mechanical properties of cast titanium

Objective. The aim of this study was to investigate the effect of laser surface treatment on the mechanical properties of cast titanium and to compare with those of the Co-Cr alloy. Methods. Dumbbell-shaped cast specimens were prepared for commercially pure titanium (grade 2) and Co-Cr alloy. The cast titanium specimens were laser-treated on the surface using a dental Nd:YAG laser machine at 240 V and 300 V. After laser treatment, tensile testing was conducted to obtain the tensile strength, percent elongation and modulus of elasticity. The hardness depth profile was made from the cast subsurface (25 mu m) to 1500 mu m in depth using the cross-sections of the cast rods with the same diameter as the dumbbell. The data were statistically analyzed by ANOVA/post hoc tests (p < 0.05). Results. The highest tensile strength was obtained for the titanium specimens laser-treated with 300V followed by the 240V and the control specimens. The laser-treated titanium specimens with 300V showed a tensile strength equivalent to the Co-Cr alloy. Although the highest modulus of elasticity was found for the specimens laser-treated with 240V, there were no significant differences in elastic modulus among 240 V, 300 V and Co-Cr. The laser-treated groups showed significantly lower hardness at the subsurface of 25 mu m and maintained their hardness until the depth of 400 mu m. The hardness of the control group was very high at 25 mu m depth, and dramatically decreased until the 200 mu m depth. Conclusion. The results of tensile testing and hardness depth-profiling indicated that the laser treatment significantly improved the mechanical properties of cast titanium by improving the surface integrity of the cast surface contamination. (C) 2008 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.