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PALLADIUM CASTING STUDY
Overview of Findings: FEM Palladium Casting Study
By Linus Drogs / Palladium Jewelry Casting Consultant, Palladium Alliance International
Palladium Alliance International (PAI) and Forschungsinstitut Edelmetalle & Metallchemie (FEM) recently
conducted a deliberate and intense study on Palladium Casting. After reading and studying the report,
it is my professional opinion that several procedural “do’s” and “don’ts” have been established. I believe
that by incorporating these findings into recommended practices and procedures, improved casting of
palladium will result.
My recommendations pertain to the three primary variables of casting palladium alloys. These variables are
melting parameters, refractory materials and casting parameters.
PALLADIUM CASTING PARAMETERS
- High flask temperatures and moderate speeds are suggested
- An optimum feed-sprue system is required
- Absorbed gas will release during solidification
- Optimum choice is a multiple-sprue system
- Reduction of centrifugal forces leads to smoother as-cast surfaces
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Palladium: An Introduction
In a series of technical briefs extracted from their evolving palladium technical manual, Palladium - An Introduction, Johnson Matthey New York identify the optimal manufacturing opportunities for this intriguing ’new’ metal.
To receive a copy of Palladium - An Introduction in both PDF and CD formats, visit the Johnson Mathey New York website.
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MELTING PARAMETERS AND METAL CHARACTERISTICS
- Palladium is able to absorb large quantities of oxygen
- Palladium tends to decompose refractory material
- Argon protection minimizes reaction of refractories
- Addition of a vacuum removes source of gas porosity
- Full vacuum increases reactivity with investment
- Evacuation of the casting chamber followed by argon backfill is optimal
- Melting range should be between 2822° F-3002° F
- Three (3) cycles of a 60-70% recycling material was used
- Some reasons for embrittlement are exposure to hydrogen, humidity and corrosive atmospheres
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INVESTMENT MATERIALS AND CRUCIBLE OPTIONS
- Both 1 part and 2 part investments will produce gas porosity-free castings
- Palladium is prone to investment reaction
- A casting process with vacuum is sensitive to poorly prepared investment
- Decomposition of crucible material was not identified as a concern
- Zirconium Oxide coatings were used in the testing
- Pre-heating crucibles prolonged lifetime
