Comparative study on torsional strength, ductility and fracture characteristics of laser-welded alpha+beta Ti-6Al-7Nb alloy, CP Titanium and Co-Cr alloy dental castings.
OBJECTIVE
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 220V or 260V of laser voltage. After being laser welded, all cast specimens were tested with a multi-axial hydraulic testing machine (MTS 858 Mini Bionix) 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.


CONCLUSIONS
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.
Department of Prosthodontics, Faculty of Dentistry, Chulalongkorn University, Henri-Dunant Road, Bangkok 10330, Thailand. Viritpon.S@chula.ac.th
Viritpon
V
Srimaneepong
Takayuki
T
Yoneyama
Equo
E
Kobayashi
Hisashi
H
Doi
Takao
T
Hanawa
D002858:Chromium Alloys / Q000737:chemistry*; D003722:Dental Alloys / Q000737:chemistry*; D003734:Dental Casting Investment / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry; D012994:Dental Soldering / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D053844:Lasers, Solid-State; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D018583:Pliability; D013314:Stress, Mechanical; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*; D054159:Torsion, Mechanical
D002858:Chromium Alloys; D003722:Dental Alloys; D003734:Dental Casting Investment; D003764:Dental Materials; C070282:Ti-6Al-7Nb alloy; D014025:Titanium