15: Precious metal alloys

15

Precious metal alloys

Figure 15.1 Face-centered tetragonal superlattice of AuCu.

c15-fig-0001


Box 15.1 Requirements of casting alloys
Castability
Solderability
Accuracy of fit
Mechanical strength
Corrosion resistance


Box 15.2 Noble metals
Gold
Platinum
Palladium
Iridium
Rhodium
Osmium
Ruthenium

Table 15.1 Effect of hardening on gold alloys

As-cast Hardened
Proportional limit (MPa) 359 587
Tensile strength (MPa) 483 794
Elastic modulus (GPa) 97 100
Elongation (%) 15 5
Hardness (BHN) 130 220

Table 15.2 Dental gold casting alloys

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Table 15.3 Average properties of dental casting alloys

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Table 15.4 Average properties of low-gold casting alloys

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Table 15.5 Casting conditions for low-gold alloys

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Table 15.6 Heat treatments for gold alloys

Hardening Softening
Heat at 450° for 2 minutes
Slow cool to 250° over 30 minutes
Water quench to room temperature
or
Heat at 350° for 10–15 minutes
Water quench to room temperature
Heat to 700°
Water quench to room temperature

Table 15.7 Casting defects

Problem Possible cause

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Jan 1, 2015 | Posted by in Dental Materials | Comments Off on 15: Precious metal alloys
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