Comparative study on torsional strength, ductility and fracture characteristics of laser-welded α plus β Ti-6Al-7Nb alloy, CP Titanium and Co-Cr alloy dental castings

Objectives. The purpose of this study was to compare torsional strength, ductility and fracture behaviors of Ti-6Al-7Nb, CP Ti and Co-Cr alloy castings after laser welding. Methods. Dumbbell-shaped castings of three metal alloys (Ti-6Al-7Nb alloy, CP Ti, Co-Cr alloy) were cut in half and laser welded with a Nd:YAG pulse laser-welding machine at either 220 V or 260 V of laser voltage. After being laser welded, all cast specimens were tested with a multi-axial hydraulic testing machine (MTS 858 Mini Bionix (R)) using a torsional test. The fracture surfaces were investigated with a scanning electron microscope. Results. None of the laser-welded Ti-6Al-7Nb alloy and CP Ti castings was broken within the welded joint, showing torsional strength as high as the unwelded castings. Unlike the other groups, the laser-welded Co-Cr alloy castings exhibited brittle fracture appearance and provided substantially less torsional strength. Significance. The torsional strength of the laser-welded Ti-6Al-7Nb alloy and CP Ti castings was as high as that of the unwelded castings while this finding could not apply to the Co-Cr alloy castings. This indicates that the mechanical strength of the laser-welded Ti-6Al-7Nb alloy dental casting is sufficient for clinical applications. (C) 2007 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.