Effect of heat treatment on joint properties of laser-welded Ag-Au-Cu-Pd and Co-Cr alloys.
OBJECTIVE
This study investigated the effect of heat treatment on the strengths of laser-welded cast Ag-Au-Cu-Pd and Co-Cr alloys.


METHODS
Cast plates of Ag-Au-Cu-Pd (Ag) and Co-Cr (Co) alloys were prepared. After polishing the surfaces to be welded, the plates were matched and butted Ag to Ag (Ag/Ag), Co to Co (Co/Co), and Ag to Co (Ag/Co) and welded using Nd:YAG laser at a pulse duration of 10 ms, spot diameter of 1 mm, and voltage of 200 V. Five specimens were prepared for each experimental condition by bilaterally welding them with five spots. The Ag/Ag, Ag/Co, and control Ag underwent two heat treatments-softening (ST) and hardening (AH). A group of as-cast specimens serving as controls was not given either heat treatment. The failure load and percent elongation were measured at a crosshead speed of 1.0 mm/min.


RESULTS
The fracture resistance of Co/Co was similar to that of the control Co, while the fracture resistance of Co/Ag was significantly lower than that of both like alloy pairings for all heat-treating conditions. The control Ag had greater fracture resistance after AH and lower fracture resistance after ST. The AH treatment increased the fracture resistance, and the ST treatment decreased the fracture resistance of both Ag/Ag and Co/Ag, although not significantly. The percentage of elongation appeared to positively correlate with the fracture resistance results.


CONCLUSIONS
The results obtained in this study indicated that the age-hardening heat treatment increased the weld strength between the paired Au-Ag-Cu-Pd alloys and between the Au-Ag-Cu-Pd and Co-Cr alloys.
Watanabe
Ikuya
I
Department of Biomaterials Science, Baylor College of Dentistry, Texas A&M University System Health Science Center, Dallas, TX 75246, USA. iwatanabe@bcd.tamhsc.edu
Benson
Andrew P
AP
Nguyen
Khoi
K
D002858:Chromium Alloys; D003035:Cobalt; D003722:Dental Alloys; D012994:Dental Soldering / Q000295:instrumentation / Q000379:methods*; D003799:Dental Stress Analysis; D004868:Equipment Failure; D006244:Hardness; D006358:Hot Temperature; D007834:Lasers; D008422:Materials Testing; D013718:Tensile Strength; D014896:Welding / Q000295:instrumentation / Q000379:methods
C120982:Ag-Pd-Cu-Au alloy; D002858:Chromium Alloys; D003722:Dental Alloys; D003035:Cobalt