Jewelry Alloys

Platinum Alloys for Jewelry

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Platinum 95% Ruthenium 5%

950 Platinum Ruthenium (950PtRu) is the most widely used platinum jewelry alloy in the United States. With a hardness of 130 Vickers, it is malleable enough for easy setting but strong enough to stand up to daily wear. Its natural white color is nearly identical to platinum-iridium alloys often seen in antique jewelry.

 

As-Cast Properties

BrilliantPt™ with HIP Properties

Yield Strength:32.6 ksi34.2 ksi
Ultimate Tensile Strength:59.7 ksi60.9 ksi
Elongation:30%39%
Reduction of Area:55%87%
Vickers Hardness (HV0.5):130130

 

Pro Tip: 950PtRu has a greater tendency to form porosity during casting than most other alloys, but this is easily healed through Hot Isostatic Pressing (HIP).

Platinum 95% Cobalt 5%

950 Platinum Cobalt (950PtCo) is unmatched for filling fine cross-sections and design details. PtCo has the greatest molten flow capability of any platinum jewelry alloys on the market and has a good hardness of 135 Vickers. Its color has a slight blue hue compared to 950PtRu.

As-Cast Properties

BrilliantPt™ with HIP Properties

Yield Strength:31.9 ksi27.4 ksi
Ultimate Tensile Strength:65.5 ksi65.1 ksi
Elongation:36%38%
Reduction of Area:76%82%
Vickers Hardness (HV0.5):135135

 

Pro Tip: 950PtCo is slightly magnetic and oxidizes when exposed to heat. While this might be troubling on the bench, but the oxidation is easily removed. 950PtCo is often preferred for its ability to cast fine designs and polish more quickly.

Platinum 95% Ruthenium-Gallium- 5%

950 Platinum Hard Cast (950PtHCA) is a harder platinum jewelry alloy that offers extra protection against wear and distortion. The 5% Ruthenium-Gallium offers superior hardness at 180 Vickers. It has a natural white color nearly identical to 950PtRu.

As-Cast Properties

BrilliantPt™ with HIP Properties

Yield Strength:N/A ksiN/A ksi
Ultimate Tensile Strength:N/A ksiN/A ksi
Elongation:N/A%N/A%
Reduction of Area:N/A%N/A%
Vickers Hardness (HV0.5):180180

 

Pro Tip: 950PtHCA is excellent for hard-on-jewelry customers who tend to abuse their rings. This jewelry alloy has lower molten flow capability so extra care is required in design to fill thin or delicate areas.

Platinum 90% Iridium 10%

Widely used for years in both casting and fabrication, 900PtIr and 950PtIr have been demonstrated to be too soft for jewelry applications when used purely in cast form. Both anecdotal and scientific research confirm this fact, so we actively encourage jewelers to switch to one of our other jewelry  alloys due to their greater wear resistance.

As-Cast Properties

BrilliantPt™ with HIP Properties

Yield Strength:31.7 ksi32.7 ksi
Ultimate Tensile Strength:51.1 ksi51.2 ksi
Elongation:33%36%
Reduction of Area:90%87%
Vickers Hardness (HV0.5):110110

More Jewelry Alloys to Explore

316L Stainless is the workhorse alloy for the jewelry industry’s stainless needs. It is composed of approximately 60% iron, 18% chromium, and 14% nickel, with small percentages of molybdenum, manganese, and others. Despite the fact that 316L has 14% nickel, it is still considered among the most biocompatible of the stainless series. It has been used in the medical industry for heart stents and spinal implants, amongst others. Nevertheless, it is important to be aware of the risk for nickel sensitivity when using this as a jewelry alloy. This is particularly true for piercing designs where, ironically, it is the most popular.

Other benefits of 316L are its rust resistance and malleability—both key factors for jewelry use. Stones can be set with relative ease and rust is better inhibited by the specific combination of elements used in 316L versus other stainless steels.

Stainless steel is priced in two ways, either by a full or partial flask as follows:

  • Full Flask:  For this option we will fit as many pieces of your jewelry design as reasonably possible into a 5 ½” x 7” flask.
  • Partial Flask:  For this option you will share your flask with another customer and will pay only for the portion of the flask that you consume.
  • Minimum Charge:  We have a $125.00 minimum charge that applies to one-off orders for stainless steel jewelry castings.  This pricing does not apply to large pieces such as bangle bracelets or other designs that consume large portions of the flask.

For the pricing on full or partial flasks, please call 503-652-5224 or send an email to info@techformcasting.com and we will be happy to advise you.

Cobalt-Chrome as a Jewelry Alloy

Cobalt-chrome is an alloy composed of approximately 67% Cobalt, 27% Chromium, and 6% Molybdenum. Renowned in the metals industry for its superb wear resistance, cobalt chrome is the metal of choice for artificial joints including knees, hips, fingers, toes, and others. As such, the metal is highly biocompatible and ideal for use in certain jewelry applications as well.

While Cobalt-Chrome has an incredible luster after high polish, it does, however, have certain limitations among the jewelry alloys. The high level of wear resistance also causes it to resist tools, making it very difficult to drill holes, set stones, or size in a traditional manner. The best use for this metal can therefore be found in pendants, earrings, cufflinks, necklaces, bracelets, etc. that do not require sizing and designs that showcase the metal versus stones. Stones, when needed, can be riveted or glued in place. Another benefit of cobalt chrome is its susceptibility to blackening. Blackening is done through a chemical process that creates a black oxide layer providing a wonderful contrast with platinum, palladium, and gold alloys. The blackening process itself is not widely published; however, many jewelers have devised their own methods for the durable blackening of this metal.