Mechanical properties of laser-welded cast titanium joints under different conditions

Statement of the problem. Data on optimal conditions for laser welding commercial pure cast titanium used in dental restorations are sparse and not well established. Purpose. The mechanical properties of laser-welded cast commercially pure titanium under different laser welding conditions were evaluated to find the optimal parameters in terms of duration and voltage (energy level). Material and methods. Fifty-seven cast pure titanium specimens according to ISO specification 6871 were divided into nine experimental groups and one control group. The sectioned titanium bars were laser welded under different duration (8, 10, and 12 ms) and energy (290, 300, and 310 V) levels and evaluated for ranges of ultimate tensile strength (374 to 562 MPa), 0.2% yield strength (206 to 338 MPa), and percentage elongation (2.49% to 10.58%). Results. Under a suitable laser-welding setting parameter the ultimate tensile strength and 0.2% yield strength of experimental groups were weaker than the unsectioned control specimens (control group ultimate tensile strength 540 +/- 11 MPa, 0.2% yield strength 258 +/- 49 MPa) or too brittle (control group percentage elongation 12.41% +/- 1.83%). Two-way ANOVA, nonparametric tests showed that voltage was the only significant factor for all parameters studied (p < 0.01). Optimal conditions were determined with three-dimensional response curves (305 V, 12 ms ultimate tensile strength; 310 V, 10 ms 0.2% yield strength; 300 V, 12 ms percentage elongation). Conclusion. Optimal duration and voltage (energy level) used in laser welding for cast CP grade I titanium bar was superior to or comparable with and produced properties that were superior to or comparable with the unsectioned control specimens.