Mechanical and elemental characterization of solder joints and welds using a gold-palladium alloy☆,☆☆,★,★★,♢
Section snippets
MATERIAL AND METHODS
Five techniques were compared: two conventional techniques, propane-oxygen torch and furnace heating, and three novel approaches, preceramic and postceramic soldering with an infrared heat source and laser welding. Comparisons were based on mechanical tests by determining the ultimate tensile strength and the resistance to fatigue failure on diffusion analysis of metal elements to and from the solder and on the evaluation of fractographs (Fig. 1). The compositions of the parent metal and the
Ultimate tensile strength
The UTS values are illustrated in Figure 4. Three groups emerged: the parent metal with a mean UTS of 812 MPa, the laser welds (633 MPa), and the furnace, torch, and IR-soldered specimens with UTSs in the 357 to 490 MPa range.
Resistance to cyclic loading
The fatigue resistance of the six joints investigated is depicted in Figure 5.
Preparation of the test specimens
Machining the Au-Pd rods instead of casting the specimens was at variance with normal laboratory procedures. Nevertheless, this approach was advisable when considering the following. First, the production cost of the rods was markedly reduced when they were industrially manufactured instead of being cast individually and, second, machining the specimens excludes significant variations in the parent metal, because what is being tested is the solder joint not the parent metal. Whether the heat
CONCLUSION
Although they were not included as variables in this investigation, two technical aspects should be mentioned. First, it was nearly impossible to maintain both rods in their original relationship during laser welding. The initial welding impact always distorted the coaxial arrangement, which could be somewhat reestablished by a second weld on the opposite side. A welding technique that ensures uniform stress distribution during joint formation is needed. Second, both the laser and the IR
Acknowledgements
The help of the following persons is gratefully acknowledged: Dr. C. Susz, for his technical advice and for supplying the alloys tested, Dr. R. Barraud for his helpful hints and suggestions, Messrs. G. Devenoge and D. Werner for their help in specimen preparation for SEM and microprobe analyses.
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Cited by (0)
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a Lecturer, Division of Fixed Prosthodontics.
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b Research Associate, Institute of Mineralogy and Petrography, University of Lausanne.
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c Professor and Chairman, Division of Fixed Prosthodontics.
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Reprint requests to: Dr. H. W. A. Wiskott Division of Fixed Prosthodontics School of Dentistry University of Geneva 19, Rue Barthelemey-Menn 1205 Geneva SWITZERLAND
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0022-3913/97/$5.00 + 0. 10/1/81596