Optimizing mechanical properties of laser-welded gold alloy through heat treatment.
OBJECTIVE
The goal of this work was to improve the mechanical strength of laser-welded gold alloy with age-hardenability at intraoral temperature.


METHODS
The gold alloy was cast conventionally in plate patterns (0.5 mm x 3.0 mm x 20 mm). After bench-cooling the mold to room temperature (as-cast state), transverse sections of the plate were made at mid-span. They were butted against one another and welded using Nd:YAG laser (current: 320 A; time: 10 ms; spot diameter: 1 mm). Three laser pulses were applied from both sides to cover the joint width (3.0 mm) of the specimens before or after solution heat treatment at 700 degrees C/5 min. Uncut control specimens (non-welded) were also prepared. After solution treatment, two different heat treatments were given the laser-welded specimens: high-temperature aging at 250 degrees C/15 min, or intraoral aging at 37 degrees C/3 days. Control specimens underwent all of the heat treatments after solution treatment. Tensile testing was conducted at a crosshead speed of 2 mm/min and a gauge length of 10 mm.


RESULTS
Solution treatment of the gold alloy before laser-welding did not improve the mechanical strength of laser-welded gold alloy after high-temperature aging or intraoral aging. The joint strengths of laser-welded gold alloy were improved only by solution heat treatments after laser-welding and subsequent aging treatment at high or intraoral temperatures.


CONCLUSIONS
The results of this study indicated that laser-welded cast gold alloy prostheses aged at high or intraoral temperatures produce high strength when they are solution-treated after laser-welding.
Watanabe
Ikuya
I
Department of Biomaterials Science, Baylor College of Dentistry, Texas A&M University System Health Science Center, 3302 Gaston Avenue, Dallas, TX 75246, USA. iwatanabe@bcd.tamhsc.edu
Liu
Jie
J
Baba
Naoki
N
Atsuta
Mitsuru
M
Okabe
Toru
T
D012994:Dental Soldering / Q000379:methods*; D003799:Dental Stress Analysis; D006047:Gold Alloys; D006244:Hardness; D006358:Hot Temperature; D007834:Lasers; D008422:Materials Testing; D012996:Solutions; D013314:Stress, Mechanical; D013718:Tensile Strength; D014896:Welding / Q000379:methods
D006047:Gold Alloys; D012996:Solutions