Dispersion-hardened precious-metal alloy

Abstract

The invention relates to a dispersion-hardened platinum composition comprising at least 70 wt. % platinum, the platinum composition containing up to 29.95 wt. % of one of the metals rhodium, gold, iridium and palladium, between 0.05 wt. % and 1 wt. % oxides of the non-precious metals zirconium, yttrium and scandium, and, as the remainder, the platinum including impurities, wherein between 7.0 mol. % and 11.0 mol. % of the oxides of the non-precious metals is yttrium oxide, between 0.1 mol. % and 5.0 mol. % of the oxides is scandium oxide, and the remainder of the oxides is zirconia, including oxide impurities. The invention also relates to a crucible for crystal growing, a semi-finished product, a tool, a tube, a stirrer, a fiberglass nozzle or a component for producing or processing glass made of a platinum composition of this kind and to a method for the production of a platinum composition.

Claims

1. A dispersion-hardened platinum composition comprising at least 70 wt. % platinum, the platinum composition containing up to 29.95 wt. % of one or more of rhodium, gold, iridium and palladium, the platinum composition containing between 0.05 wt. % and 1 wt. % oxides of the non-precious metals zirconium, yttrium and scandium, and the platinum composition containing, as the remainder, the platinum including impurities, wherein between 8.0 mol. % and 10.0 mol. % of the oxides of the non-precious metals are yttrium oxide, between 0.1 mol. % and 5.0 mol. % of the oxides are scandium oxide, and the remainder of the oxides are zirconia, including oxide impurities.

2. The platinum composition of claim 1, wherein the oxides of the non-precious metals zirconium, yttrium and scandium are completely oxidized at least by 70%.

3. The platinum composition of claim 1, wherein the total proportion of impurities in the platinum composition is at most 1 wt. %.

4. The platinum composition of claim 1, wherein at least 50 mol. % of the oxides of the non-precious metals are cubic zirconia stabilized with yttrium oxide and/or scandium oxide.

5. The platinum composition of claim 1, wherein the platinum composition is produced by melting metallurgy, is then rolled out and is oxidized by heat treatment in an oxidizing medium such that the non-precious metals contained in the platinum composition are completely oxidized.

6. The platinum composition of claim 1, wherein the ratio of yttrium oxide to scandium oxide in the platinum composition is in a range of from 2.6:1 to 10:1.

7. The platinum composition of claim 1, wherein between 8.0 mol. % and 10.0 mol. % of the oxides are yttrium oxide.

8. The platinum composition of claim 1, wherein between 1.0 mol. % and 3.0 mol. % of the oxides are scandium oxide.

9. The platinum composition of claim 1, wherein the platinum composition contains at least 80 wt. % platinum including impurities, and/or the platinum composition contains at least 1 wt. % rhodium, gold, palladium or iridium.

10. The platinum composition of claim 1, wherein the platinum composition contains between 5 wt. % and 20 wt. % rhodium and no gold, iridium or palladium, except for impurities, or the platinum composition contains between 2 wt. % and 10 wt. % gold and no rhodium, iridium or palladium, except for impurities.

11. The platinum composition of claim 1, wherein the platinum composition has a creep strength of at least 500 h at 1400° C. under a load of 20 MPa.

12. The platinum composition of claim 1 produced by a process, the process comprising: A) producing a melt having at least 70 wt. % platinum, up to 29.95 wt. % of one or more of rhodium, gold, iridium and palladium, between 0.05 wt. % and 1 wt. % oxidizable non-precious metals in the form of zirconium, yttrium and scandium, and, as the remainder, platinum including impurities, wherein the ratio of zirconium to yttrium in the melt is in a range of from 5.9:1 to 4.3:1 and the ratio of zirconium to scandium in the melt is at least 17.5:1, B) hardening the melt to form a solid body, C) processing the solid body to form a volume body; and D) oxidizing the non-precious metals contained in the volume body by a heat treatment in an oxidizing medium over a time period of at least 48 hours at a temperature of at least 750° C.

13. The platinum composition of claim 1, wherein the oxides of the non-precious metals zirconium, yttrium and scandium are completely oxidized at least by 90%.

14. The platinum composition of claim 1, wherein at least 80 mol. % of the oxides of the non-precious metals are cubic zirconia stabilized with yttrium oxide and/or scandium oxide.

15. The platinum composition of claim 1, wherein between 8.5 mol. % and 9.5 mol. % of the oxides are yttrium oxide.

16. The platinum composition of claim 1, wherein between 1.5 mol. % and 2.5 mol. % of the oxides are scandium oxide.

17. A crucible for crystal growing, a semi-finished product, a tool, a tube, a stirrer, a fiberglass nozzle or a component for producing or processing glass having a platinum composition according to claim 1.

18. A temperature sensor having a platinum composition according to claim 1.

Description

COMPARATIVE EXAMPLE 1

(1) 10 wt. % rhodium, 1830 ppm zirconium, 295 ppm yttrium, 50 ppm scandium and the remainder platinum including usual impurities.

(2) This corresponds to a mole fraction of the oxide of the non-precious metal in the oxidized state of the platinum composition of 7.5 mol. % Y.sub.2O.sub.3 (yttrium oxide), 2.5 mol. % Sc.sub.2O.sub.3 (scandium oxide) and the remainder ZrO.sub.2 (zirconia).

(3) The oxidation of the non-precious metals of the 3 mm thick metal sheet takes place in the air at 900° C. After an oxidation time of 27 days, >90% of the non-precious metals in the metal sheet were oxidized. The metal sheet was then ductility-annealed at 1400° C. for 6 hours and thermomechanically processed as disclosed in WO 2015/082630 A1. As a result, a creep strength of 3 hours is brought about at 1400° C. and 20 MPa and a creep strength of 50 hours is brought about at 1600° C. and 9 MPa.

COMPARATIVE EXAMPLE 2

(4) 10 wt. % rhodium, 1830 ppm zirconium, 295 ppm yttrium, 50 ppm scandium and the remainder platinum including usual impurities.

(5) This corresponds to a mole fraction of the oxide of the non-precious metal in the oxidized state of the platinum composition of 7.5 mol. % Y.sub.2O.sub.3 (yttrium oxide), 2.5 mol. % Sc.sub.2O.sub.3 (scandium oxide) and the remainder ZrO.sub.2 (zirconia).

(6) The oxidation of the non-precious metals of the 3 mm thick metal sheet takes place in the air at 1000° C. After an oxidation time of 9 days, >90% of the non-precious metals in the metal sheet were oxidized. The metal sheet was then ductility-annealed at 1400° C. for 6 hours and the metal sheet was thermomechanically processed as disclosed in WO 2015/082630 A1. As a result, a creep strength of 0.5 hours is brought about at 1400° C. and 20 MPa and a creep strength of 3 hours is brought about at 1600° C. and 9 MPa.

EXAMPLE 3 (INVENTION)

(7) 10 wt. % rhodium, 2770 ppm zirconium, 546 ppm yttrium, 63 ppm scandium and the remainder platinum including usual impurities.

(8) This corresponds to a mole fraction of the oxide of the non-precious metal in the oxidized state of the platinum composition of 9.0 mol. % Y.sub.2O.sub.3 (yttrium oxide), 2.0 mol. % Sc.sub.2O.sub.3 (scandium oxide) and the remainder ZrO.sub.2 (zirconia).

(9) The oxidation of the non-precious metals of the 3 mm thick metal sheet takes place in the air at 900° C. After an oxidation time of just 19 days, >90% of the non-precious metals in the metal sheet were oxidized. The metal sheet was then ductility-annealed at 1400° C. for 6 hours and the metal sheet was thermomechanically processed as disclosed in WO 2015/082630 A1. As a result, a creep strength of over 500 hours is brought about at 1400° C. and 20 MPa and a creep strength of over 1000 hours is brought about at 1600° C. and 9 MPa.

EXAMPLE 4 (INVENTION)

(10) 10 wt. % rhodium, 2770 ppm zirconium, 546 ppm yttrium, 63 ppm scandium and the remainder platinum including usual impurities.

(11) This corresponds to a mole fraction of the oxide of the non-precious metal in the oxidized state of the platinum composition of 9.0 mol. % Y.sub.2O.sub.3 (yttrium oxide), 2.0 mol. % Sc.sub.2O.sub.3 (scandium oxide) and the remainder ZrO.sub.2 (zirconia).

(12) The oxidation of the non-precious metals of the 3 mm thick metal sheet takes place in the air at 1000° C. After an oxidation time of just 6 days, >90% of the non-precious metals in the metal sheet were oxidized.

(13) By optimizing the molar composition, i.e. the molar ratio of the oxide-forming non-precious metals, and by increasing the total quantity of oxide-forming non-precious metals (from 2150 ppm to 3400 ppm), the invention succeeds in reducing the oxidation time in the solid body by >25% while simultaneously improving the high-temperature properties.

EXAMPLE 5 (INVENTION)

(14) 10 wt. % rhodium, 2710 ppm zirconium, 511 ppm yttrium, 65 ppm scandium and the remainder platinum including impurities. A circular blank of 200 g was produced by means of arc melting.

(15) This corresponds to a mole fraction of the oxide of the non-precious metal in the oxidized state of the platinum composition of 8.6 mol. % Y.sub.2O.sub.3 (yttrium oxide), 2.2 mol. % Sc.sub.2O.sub.3 (scandium oxide) and the remainder ZrO.sub.2 (zirconia).

(16) The oxidation of the non-precious metals of the 2 mm thick metal sheet takes place in the air at 900° C. After an oxidation time of just 10 days, >90% of the non-precious metals in the metal sheet were oxidized. The metal sheet was then ductility-annealed at 1400° C. for 6 hours and the metal sheet was thermomechanically processed as disclosed in WO 2015/082630 A1. As a result, a creep strength of over 500 hours is brought about at 1400° C. and 20 MPa and a creep strength of over 1000 hours is brought about at 1600° C. and 9 MPa.

COMPARATIVE EXAMPLE 6

(17) 10 wt. % rhodium, 1870 ppm zirconium, 313 ppm yttrium, 33 ppm scandium and the remainder platinum including usual impurities. A circular blank of 200 g was produced by means of arc melting.

(18) This corresponds to a mole fraction of the oxide of the non-precious metal in the oxidized state of the platinum composition of 7.8 mol. % Y.sub.2O.sub.3 (yttrium oxide), 1.6 mol. % Sc.sub.2O.sub.3 (scandium oxide) and the remainder ZrO.sub.2 (zirconia).

(19) The oxidation of the non-precious metals of a 2 mm thick metal sheet takes place in the air at 900° C. After an oxidation time of 20 days, >90% of the non-precious metals in the metal sheet were oxidized. The metal sheet was then ductility-annealed at 1400° C. for 6 hours and the metal sheet was thermomechanically processed as disclosed in WO 2015/082630 A1. It results in a creep strength analogously to comparative example 1.

(20) For the further comparison, three additional comparative tests were carried out in which a combination of scandium oxide and niobium oxide (Nb.sub.2O.sub.5) instead of yttrium oxide and scandium oxide was introduced into the platinum composition for stabilizing the oxygen-ion-conducting cubic zirconia phase.

(21) The platinum compositions described in the following were produced by circular blanks having individual weights of 200 g each being produced by arc melting. In this way, 3 different platinum compositions containing 10 wt. % rhodium, 200 ppm scandium and variable proportions of niobium were produced. A 2 mm thick metal sheet of the platinum composition was produced by rolling and tempering.

(22) The proportion of the oxidized non-precious metals in the platinum composition was then determined by quantitative IR spectroscopy.

COMPARATIVE EXAMPLE 7

(23) 10 wt. % rhodium, 1800 ppm zirconium, 80 ppm niobium, 200 ppm scandium and the remainder platinum including usual impurities.

(24) This corresponds to a mole fraction of the oxide of the non-precious metal in the oxidized state of the platinum composition of 2.0 mol. % Nb.sub.2O.sub.5 (niobium oxide), 10.0 mol. % Sc.sub.2O.sub.3 (scandium oxide) and the remainder ZrO.sub.2 (zirconia).

(25) The oxidation of the non-precious metals of the 2 mm thick metal sheet takes place in the air at 900° C. After an oxidation time of 20 days, only 39% of the non-precious metals in the metal sheet were oxidized.

COMPARATIVE EXAMPLE 8

(26) 10 wt. % rhodium, 1800 ppm zirconium, 40 ppm niobium, 200 ppm scandium and the remainder platinum including usual impurities.

(27) This corresponds to a mole fraction of the oxide of the non-precious metal in the oxidized state of the platinum composition of 1.0 mol. % Nb.sub.2O.sub.5 (niobium oxide), 10.0 mol. % Sc.sub.2O.sub.3 (scandium oxide) and the remainder ZrO.sub.2 (zirconia).

(28) The oxidation of the non-precious metals of the 2 mm thick metal sheet takes place in the air at 900° C. After an oxidation time of 20 days, only 42% of the non-precious metals in the metal sheet were oxidized.

COMPARATIVE EXAMPLE 9

(29) 10 wt. % rhodium, 1800 ppm zirconium, 20 ppm niobium, 200 ppm scandium and the remainder platinum including usual impurities.

(30) This corresponds to a mole fraction of the oxide of the non-precious metal in the oxidized state of the platinum composition of 0.5 mol. % Nb.sub.2O.sub.5 (niobium oxide), 10.0 mol. % Sc.sub.2O.sub.3 (scandium oxide) and the remainder ZrO.sub.2 (zirconia).

(31) The oxidation of the non-precious metals of the 2 mm thick metal sheet takes place in the air at 900° C. After an oxidation time of 20 days, only 36% of the non-precious metals in the metal sheet were oxidized.

(32) The oxidation time in comparative examples 6, 7 and 8 was therefore considerably worse than in comparative example 5. This shows that a direct conclusion cannot be drawn on the oxidizability or oxidation time of the platinum composition from the oxygen ion conductivity of the oxides.

(33) The measurements show that, for the platinum composition, there is no simple connection such that an oxide having high ion conductivity would bring about an acceleration of the oxidation process. Accordingly, the selection of non-precious metals according to the invention in the platinum composition according to the invention results in surprising success.

(34) The features of the invention disclosed in the above description, as well as in the claims, drawings and exemplary embodiments, may be essential both individually and in any combination for realizing the invention in its various embodiment forms.