RU2606679C2 - Palladium-based jewellery alloy (versions) - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy of noble metals and alloys, particularly to palladium-based alloys used in jewellery industry. According to one version alloy contains, wt%: palladium 50–95, nickel 3–5, silicon 0.5–2, boron 0.01–1.0, at least one element selected from a group comprising copper, gold, indium, gallium in amount of less than 1.0 each, at total content of nickel and silicon of up to 5 %, wherein alloy has a structure reinforced with intermetallide Ni₂Si. In another version alloy contains, wt%: palladium 50–85, nickel 11-13.5, aluminium 1.5–4, boron 0.01–1.0, at least one element selected from a group comprising copper, gold, indium, gallium, in amount of less than 1.0 each, at total content of nickel and aluminium of up to 15%, wherein alloy has structure reinforced with intermetallides Ni₃Al, NiAl, Ni₂Al₃.

EFFECT: technical result is improved strength properties and corrosion resistance of palladium alloy while maintaining level of casting properties, plasticity and white colour close to mounting plate.

2 cl, 2 ex

Description

The invention relates to the metallurgy of noble metals, in particular to palladium-based alloys intended for the manufacture of jewelry.

For a long time, palladium was used in the manufacture of alloys for jewelry production only as a ligature to a gold alloy to produce white gold. Recently, palladium began to be used as the main component of jewelry alloys. This is due to the fact that palladium, being a precious metal, is cheaper than platinum and has a number of unique properties: it is hypoallergenic, lightweight and plastic, so palladium jewelry is much lighter than gold and platinum products, which is very important for jewelry such as earrings, it has a lighter color than platinum, does not fade in air, scratches and cracks do not form on its surface, and the mirror shine lasts for decades. However, in terms of its chemical properties, palladium is inferior to platinum and other platinum group metals. In addition, unalloyed palladium has low strength properties, which are important when attaching gems to jewelry. Thus, the development of strong alloys based on palladium, which has a complex of inherent positive properties, is very promising.

Known casting alloys for jewelry based on palladium containing zinc or silicon to reduce the melting point and increase ductility (RU 2244762 C1, C22C 5/02, published January 20, 2005; RU 2479656 C1, C22C 5/04, published April 20, 2013) . Alloys have good fluidity, which contributes to the production of products from them by casting with high accuracy, however, these alloys have an insufficient level of mechanical properties, which does not allow their wide use to obtain products by shaping.

Known is a palladium-based jewelry alloy containing nickel and platinum, in which boron and zirconium are introduced to increase strength (RU 2395604 C1, C22C 5/04, published July 27, 2010). However, the strength of the alloy is insufficient for the manufacture of jewelry with stones, and the content of platinum in the amount of 12-15% significantly increases its cost.

Known jewelry alloy based on palladium, containing, by weight. %: 3.0-5.4 nickels, 5.0-10.0 copper, 0.5-1.5 zinc, 0.2-0.8 indium, 0.2-1.0 gallium, 85.0 -90.5 palladium (RU 2331683 C2, C22C 5/04, published 03/20/2008). The alloy is similar in appearance to platinum alloys, has a low nickel content, but has a low hardness. The specified alloy is accepted as the closest analogue.

The problem to which the invention is directed, is to create an alloy based on palladium, having a white color, close to platinum, which has the optimal physical and mechanical properties for jewelry manufacturing.

The technical result of the invention is to increase the strength properties, especially hardness, of a palladium alloy while maintaining the level of casting properties, ductility and white color close to platinum.

The technical result is achieved in that the palladium-based alloy for the manufacture of jewelry containing nickel additionally contains silicon, boron and at least one element selected from the group consisting of copper, gold, indium, gallium, in the following ratio of components, wt. %:

palladium 50-95 nickel 3-5 silicon 0.5-2 boron 0.01-1.0

at least one element selected from the group consisting of copper, gold, indium, gallium in an amount of less than 1.0 each, with a total nickel and silicon content not exceeding 5%, while the alloy has a structure hardened by intermetallic Ni ₂ Si .

In another embodiment of the invention, the technical result is achieved in that the palladium-based alloy for the manufacture of jewelry containing nickel and palladium additionally contains aluminum, boron and at least one element selected from the group consisting of copper, gold, indium, gallium, in the following ratio of components, wt. %:

palladium 50-85 nickel 11-13.5 aluminum 1,5-4 boron 0.01-1.0

at least one element selected from the group containing copper, gold, indium, gallium, in an amount of less than 1.0 each, with a total nickel and aluminum content not exceeding 15%, the alloy having a structure strengthened by nickel aluminides.

The invention consists in the following.

Increasing the hardness of alloys is very important for jewelry, as allows you to maintain their shine after polishing for a longer time and reduces the number of scratches. The claimed alloys have the ability to harden during thermal or thermomechanical processing, while they have a relatively low melting point and good processability during casting, hot and cold deformation.

The hardening of the claimed palladium alloys is based on the effect of dispersion hardening. The heat treatment of precipitation hardening alloys consists in heating them to form a supersaturated solid solution, followed by rapid cooling (quenching) and aging. As a result of such heat treatment, the solid solution decomposes with the release of nanophase particles of phases - hardeners. The strengthening effect is achieved due to the composition of the formed and released intermetallic compounds. The difference from hardeners of a different composition is significant both in the method of formation and in the structure, nature of the melting points, kinetics of decomposition of the solid solution, the effect of hardening and its stability. The method of hardening palladium alloys used for the manufacture of jewelry by using the dispersion hardening effect, which provides the necessary processability in the process of their manufacture and operation, involves doping the palladium base with two components that form a chemical compound between themselves. Nickel and silicon are used as such components in one embodiment of the invention, and nickel and aluminum in another embodiment. Their quantitative content in alloys is determined by the stoichiometric ratio necessary for the formation of intermetallic compounds Ni ₂ Si and Ni ₃ Al, NiAl, Ni ₂ Al _3, respectively.

Being a deoxidizing agent, boron in an amount of 0.01-1% reduces the effect of oxygen during smelting of alloys, reduces the loss of alloying components on fumes and reduces grain size.

Alloying the alloy in any combination with copper, gold, indium, gallium ensures a decrease in the melting point of the palladium alloy, an increase in casting properties and density of the product. The limitation of their quantitative content is less than 1.0 each due to the preservation of the color of the alloy close to platinum.

Examples of the invention

Example 1

The alloy of the following chemical composition was obtained:

Pd - base, 3.2% Ni, 1.1% Si, 0.08% B, 0.08% Au, impurities not more than 0.1%.

Melting was carried out in a vacuum furnace of resistive heating. An artificial sapphire crucible with charge materials was placed in a heated graphite crucible. Melting was carried out at a temperature of 1730 ° C. Cylindrical ingots with a diameter of 30 mm and a height of 8 mm were obtained. It should be noted that the introduction of boron increased the fluidity of the alloys and led to a decrease in linear shrinkage. Structural analysis showed a decrease in grain size. This significantly improves the consumer properties of these alloys.

The claimed alloys are dispersion hardening, therefore, in order to increase their hardness, work was carried out on the selection of heat treatment modes (hardening + aging), as a result of which heating and holding temperatures for hardening were set, ranging from 950 to 1150 ° C and from 10 to 30 minutes, respectively, and the aging and aging ranges from 450 to 600 ° C and from 2 to 4 hours, respectively.

In a specific implementation example, quenching was carried out in water after holding the alloy at a temperature of 1000 ° C for 15 minutes. After that, the alloy was aged at a temperature of 490 ° C for 4 hours.

The hardness of the alloy after heat treatment was 200 HB, which was almost two times higher than the hardness of cast alloys with solid solution hardening. The alloy had a beautiful warm shade, due to the introduction of gold into it within the specified limits, while maintaining a characteristic white color and luster. This became apparent after polishing using standard pastes used in jewelry production.

Example 2

An alloy was obtained containing Pd - base, 11.8% Ni, 2.8% Al, 0.07% B, 0.08% Au, and impurities no more than 0.1%.

Melting was carried out analogously to example 1 at a temperature of 1730 ° C. Quenching in water was carried out after holding the alloy at a temperature of 1000 ° C for 15 min. Aging was carried out at a temperature of 520 ° C with an exposure of 4 hours.

The alloy obtained after heat treatment had a hardness of 300 HB, which is ninety units higher than the hardness of the cast alloy of 210 HB, while maintaining the platinum color of the alloy.

Thus, the claimed alloys have an optimal level of hardness and have a beautiful white color while maintaining high casting properties and plasticity, which allows them to produce high-quality jewelry with the required properties.

Claims (8)

1. An alloy based on palladium for the manufacture of jewelry containing nickel, characterized in that it additionally contains silicon, boron and at least one element selected from the group consisting of copper, gold, indium, gallium, in the following ratio of components , wt.%: palladium 50-95 nickel 3-5 silicon 0.5-2 boron 0.01-1.0 at least one item selected from a group containing copper, gold, indium, gallium in an amount of less than 1.0 each, with a total nickel and silicon content of up to 5%, while the alloy has a structure hardened by intermetallic Ni ₂ Si. 2. An alloy based on palladium for the manufacture of jewelry containing nickel, characterized in that it additionally contains aluminum, boron and at least one element selected from the group consisting of copper, gold, indium, gallium, in the following ratio of components , wt.%: palladium 50-85 nickel 11-13.5 aluminum 1,5-4 boron 0.01-1.0 at least one item selected from groups containing copper, gold, indium, gallium, in an amount of less than 1.0 each, with a total nickel and aluminum content of up to 15%, the alloy having a structure hardened by intermetallic compounds Ni ₃ Al, NiAl, Ni ₂ Al ₃ .