JPH10195561A - Heat resistant platinum material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a platinum material having slight crystalline grain growth as well as creep rupture strength as high as possible at high temp. and capable of being easily manufactured by melt metallurgy by specifying a composition consisting of Hf, one element among Y, La, and Gd, and Pt. SOLUTION: The platinum alloy as a ternary alloy consisting of platinum and transition elements has a composition consisting of, by weight, 0.1-0.4%, preferably 0.2-0.4%, of Hf, 0.1-0.4%, preferably 0.15-0.3%, of one element among Y, La, and Gd, and >=99.5% of Pt. It is preferable to obtain this alloy by preparing a prealloy of Pt as a base material and alloy components by the use of a ZrO2 crucible in a vacuum induction melting furnace and further accurately regulating small amounts of working metallic additives. By the addition of Hf, the mixed crystal hardening of Pt and the solubility of Y, La, and Gd and be improved, and further, the effect of addition of the other element can be produced only in the case where Hf is a second matrix metal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heat-resistant platinum material containing at least 99.5% by weight of platinum and a rare earth element.

[0002]

BACKGROUND OF THE INVENTION Heat-resistant platinum materials can be used for many applications in industry and in the laboratory, with particular demands on mechanical, thermal and chemical stability. A special field of application is glass melting technology, in which platinum melting crucibles and platinum structural parts are increasingly used for the production of highly pure and homogeneous optical glass for flat screens, television cathode ray tubes, PC monitors and glass fibers. Proven suitable.

[0003] Various technical solutions are known for improving the high-temperature strength of platinum in long-term use. The most efficient method is to use a small amount of thermally stable, hard and insoluble matrix metal particles having a particle size of less than 50 nm,
Uniformly dispersed, based on dispersion hardening. This kind of dispersion prevents dislocation movement in the lattice and thus macroscopic deformation at long loading times and high temperatures. The dispersion thus prevents premature damage of the material due to the formation of coarse particles and slippage of the viscous particles.

[0004] Various variants of powder metallurgy are used to produce the material, but this is fundamentally expensive and is not always applicable given the various use requirements. Not exclusively.

[0005] Also mentioned are production methods which are based on customary melt metallurgy and which attempt to achieve grain size stabilization and structure hardening by means of alloy technology. This basically uses a combination of precipitation hardening (dispersion hardening by homogeneous but not thermally stable particles), mixed crystal hardening and grain boundary deflection mechanisms.

[0006] Thus, for example, the addition of small amounts of boron to a platinum / zirconium alloy results in a material of this kind with a high creep rupture strength and a stable particle (DE-A-195 31 342). This results in 0.21% by weight of zirconium and 0.009% of boron.
A platinum alloy having a wt.% Achieves a creep rupture strength of 4.3 MPa at 1300 ° C. for 100 hours, whereas only the creep rupture strength of 2.2 MPa without boron addition is achieved. Yes (pure platinum is only 1.8 MPa under the same conditions).

Investigations on alloys of platinum with rare earth metals have shown that, although improved strength can be achieved, the very limited solubility of these elements in platinum is not sufficiently practical. It is known. Already upon hardening, relatively coarse intermetallic deposits occur with little effect on strength.

Another document (Platinum Metals Review, 1995)
(39), 167-171) report a heat-resistant platinum material based on the synergistic effect of the addition of zirconium and yttrium. A compound of yttrium and zirconium is assumed as a hardening phase. However, the material does not yet have optimal properties with respect to high temperature strength.

[0009]

It is therefore an object of the present invention to contain more than 99.5% of platinum and rare earths, to have as high a creep rupture strength as possible at high temperatures and to have a small grain growth, and to be easy to use. To provide a heat-resistant platinum material that can be manufactured by melt metallurgy.

[0010]

According to the present invention, there is provided, according to the present invention, 0.1 to 0.4% by weight of hafnium and 0.1 to 0.4% by weight of yttrium and / or lanthanum and / or gadolinium in total. The balance is solved by a platinum material containing at least 99.5% by weight of platinum.

Advantageously, the material comprises at least 99.
5% by weight, 0.2 to 0.4% by weight of hafnium and 0.15 to 0.3% by weight in total of yttrium and / or lanthanum and / or gadolinium.

The mode of action of the addition of hafnium is based on the mixed crystal hardening of platinum and the increasing solubility limits for the elements yttrium, gadolinium and lanthanum. Concentrations less than 0.1% by weight of hafnium have no significant effect in this regard, and additions above 0.4% by weight (in relation to other ternary additives) degrade the desired properties.

[0013] Precipitation hardening is achieved by a stable intermetallic phase, eg, Y
Pt ₃ , YPt ₅ , GdPt ₅ , GdPt ₂ , LaPt ₅ ,
Based on the formation of LaPt ₂ , HfPt ₃ and HfPt ₅ . In this case, if the concentration of hafnium exceeds 0.4% by weight, the solubility in the solid state is clearly exceeded,
And the phase already has relatively coarse crystals (> 10 μm) upon curing.
m). This clearly has a detrimental effect on creep rupture strength. 0.1
If it is less than% by weight, the volume fraction of the precipitated phase is significantly reduced, and thus also an undesired reduction in strength.

It has been found that the combination of alloying elements produces a clear effect, that is, only when hafnium is the second matrix metal, additives to the alloy of yttrium, gadolinium and lanthanum lead to the effect described. Appropriate concentrations of the individual elements (yttrium, hafnium, gadolinium and lanthanum) do not have the results that ternary alloys achieve.

Surprisingly, when the rare earth content is the same, the addition of hafnium gives a better value for the creep rupture strength at 1200 ° C. than using the same amount of the known additive element zirconium. Is achieved. It has been found that the intermetallic phase of hafnium with platinum and rare earths is more stable than the intermetallic phase with zirconium, and that hafnium imparts basic strength to platinum.

Advantageously, in order to produce the material, small amounts of the working metal additive can be adjusted as precisely as possible.
We start by pre-alloying with the base material platinum. In this sense, the prealloys according to Table 1 are produced for the examples.

[0017]

The following examples illustrate the invention in detail.

1. Pure platinum 1000g, pre-alloy PtHf3
(No. F) 150 g and pre-alloy PtY2.6 (N
o.G) 45 g was melted in a vacuum induction melting furnace in a zirconium oxide crucible under argon under a pressure of about 200 mbar;
And cast into a copper mold, small metal (size 50 × 30 × 1
5 mm). 1200 to homogenize the casting metal
C. for 8 hours in air, and quenched with water. Subsequently, the casting surface was removed by a milling machine to remove a thickness of about 1.0 mm, and a sheet metal having a thickness of 0.5 mm was produced from the base metal by ordinary temperature rolling. After the final annealing (0.5 hours, 1000 ° C.), the characteristic values shown in Table 2 were confirmed. The target composition of the alloy is PtHf / Y
0.38 / 0.10%.

2. Pure platinum 1000g / pre-alloy PtHf3
(No. F) 95 g and pre-alloy PtY2.6 (No.
G) 90 g were produced as in Example 1 and processed into sheet metal. The material property values are likewise described in Table 2. The target composition is PtHf / Y 0.25 / 0.22%.

3-5. The other three alloys were prepared in the same manner as in Examples 1 and 2 by changing the Hf and Y contents in each case.
Manufactured in the t-Hf-Y system and tested. The results are also listed in the table. The alloy according to Example 5 is outside the range according to the invention in Hf content and therefore has a relatively low high-temperature strength.

6. 500g pure platinum, pre-alloy PtHf3
60 g, and 6 g of the pre-alloy PtGd19.2 (A) were coated with a powder suspension of Gd ₂ O _{3 in} a vacuum induction melting furnace.
In an O ₂ crucible, melted at 1000 mbar under argon and cast into a copper mold, a small metal (about 60 × 40
× 10 mm). The castings were subsequently processed as described in 1 and 2 and then the material samples were subjected to similar strength tests. See Table 2 for results. The target composition is PtHf / Gd 0.32 / 0.20%.

7. 500g pure platinum, pre-alloy PtHf3
60 g and 6 g of the prealloy PtLa 19.6 (B) were prepared in a manner analogous to Example 6, and subsequently Examples 1 and 2
Was processed into a test material having a thickness of 0.5 mm according to the description. The results are shown in Table 2. The target composition is PtHf / La
0.32 / 0.17%.

For comparison, Table 2 lists some known heat-resistant platinum materials according to the prior art (8-14).
Of particular interest is the comparison of Examples 2 and 13. The only difference is that the alloy of 2) contains 0.25% by weight of hafnium and the alloy of 13) contains 0.25% by weight of zirconium instead of hafnium. Zirconium-containing platinum alloys have substantially lower creep rupture strength than hafnium-containing alloys.

[0024]

[Table 1]

[0025]

[Table 2]

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Stephann Zeuiner Germany Friedrichsdorf Albert-Schweizer-Strasse 16

Claims (2)

[Claims] 1. A heat-resistant platinum material in the form of a ternary alloy comprising platinum and a transition element, said alloy comprising hafnium 0.5.
Heat-resistant platinum, characterized in that it comprises 1 to 0.4% by weight, 0.1 to 0.4% by weight of one element of yttrium, lanthanum or gadolinium and the balance at least 99.5% by weight of platinum. material. 2. The heat-resistant platinum material according to claim 1, wherein said alloy contains 0.2 to 0.4% by weight of hafnium and 0.15 to 0.30% by weight of an element yttrium, lanthanum or gadolinium.