KR101231936B1 - Nickel-based semifinished product having a cube recrystallization texture, corresponding method of production and use - Google Patents

Abstract

The present invention relates to nickel-based semifinished products having a cube recrystallized texture, and methods and uses for their preparation. Semifinished products can be used, for example, as a support for physicochemical coatings having a high microstructural arrangement. Such a support is suitable as a substrate for ceramic coatings, for example as used in the field of high temperature superconductors. In these cases, the product is used in superconducting magnets, transformers, motors, tomography and superconducting current paths. It is an object of the present invention to provide a nickel-based semifinished product having improved performance characteristics when used as a support for physicochemical coatings having a high microstructural arrangement. In particular, the semifinished product should have a higher, thermally more stable cube structure, substantially inhibiting the formation of grain size grooving. For this purpose, Ag in the microalloy range is added to the semifinished material, and the added Ag is 0.3 atomic% or less. The semifinished products of the invention are suitable, for example, as supports for physicochemical coatings having a high microstructural arrangement.

Description

NICKEL-BASED SEMIFINISHED PRODUCT HAVING A CUBE RECRYSTALLIZATION TEXTURE, CORRESPONDING METHOD OF PRODUCTION AND USE}

The present invention relates to a nickel-based semifinished product having a cube recrystallized texture and a method for producing the same.

Semifinished products can be used, for example, as a base for physicochemical coatings arranged in highly microstructured structures. The base is suitable as a substrate for ceramic coating, for example as used in high temperature superconducting applications. In this case the semifinished product is used in superconducting magnets, transformers, motors, tomographs or superconducting current paths.

It is known that polycrystalline metals comprising cube surface centered grids, ie nickel, copper and aluminum, etc., can form an aggregate with a cube state upon subsequent recrystallization after a strong cold forging preceded by rolling (G. Wassermann : Aggregation of Metallic Materials, Springer Press, Berlin, 1939. Metal strips assembled in this manner, in particular nickel strips, are used as bases for metal coatings, ceramic buffer layers and ceramic superconducting layers. Suitability of the metal strip as a substrate material mainly depends on the degree of achievement of the texture and the stability of the texture within the temperature range in which the coating process is carried out.

Semi-finished products for the production of high temperature superconductors are known, which are composed of Ni-Cr, Ni-Cr-V, Ni-Cu and similar alloys (US 5, 964, 966; US 6, 106, 615).

Ni alloys containing Mo and W are also known for this purpose (DE 100 05 861 C1).

Known semifinished products have the following disadvantages.

Nickel has a very strong tendency to form coarse structures that are undesirable to achieve high cube texture after cold forging and recrystallization annealing.

Cold forged Ni strips have a very strong tendency to form grain boundary grabs, especially at higher temperatures (800-1500 ° C.) during recrystallization heat treatment.

Grain size grabs can significantly prevent the formation of highly biaxial cube textures.

Substrate materials comprising grain size grabs are not very suitable as bases for epitaxial layer deposition, such as buffer and superconducting layers.

It is an object of the present invention to provide a nickel-based semifinished product having improved use properties for use as a base for physicochemical coatings arranged in a microstructure. In particular, the semifinished product shall have a highly and thermally stable cube texture and should be prevented to form grain size grabs. It is also included in the object to provide a method for producing the semifinished product.

This object is achieved by the material of the semifinished product comprising Ag additives in the microalloy range, wherein the Ag additive is at most 0.3 atom-%.

According to a preferred embodiment of the invention the Ni alloy may comprise Mo and / or W as the alloying element.

The semifinished product may be provided with a cube textured NiO layer having an amount of texture greater than 90% in accordance with the present invention. The layer is suitable as a diffusion barrier and can form a high quality coating layer, especially under oxidizing conditions.

The Ag additive according to the present invention supports the formation of high cube texture and prevents the formation of grain size grabs on the Ni surface of the semifinished product. Ag additives also allow for high epitaxial growth by NiO layers with cube texture in semi-finished products.

The method according to the invention for the production of semifinished products is characterized in that the semifinished products are first produced by smelting metallurgy or powder metallurgy, taking into account mechanical alloying, the semifinished products technically having an Ag additive in the microalloy range. It is composed of a pure Ni or Ni alloy containing, the additive is 0.3 atom-% at the maximum. The semifinished product is then processed into strips or flat wires by subsequent high cold forging with a thickness reduction of more than 80% through hot forging. Finally the product can be recrystallized annealed to achieve a cube texture.

After or during recrystallization annealing, the semifinished product prepared above may be heat treated in an oxidizing atmosphere for epitaxial growth of the cube textured NiO layer according to the present invention.

The semifinished product can be used according to the invention, in particular as a base for physicochemical coatings arranged in highly microstructured structures for the production of high temperature superconductors in the form of wires or strips.

The invention is illustrated in detail by the examples which follow, which illustrate the successful implementation of the invention. Some of the implementation results are recorded in FIGS. 1 and 2 and Table 1 below.

Example 1

Functionally pure nickel with a purity of 99.9 atom-% Ni is transferred to the die cast under an alloy of 0.01 atom-% silver. The ingot is rolled into a cube structure (22 × 22) mm 2 at 1000 ° C., annealed and metallized while homogenized. Subsequently the cube material is cut and modified to obtain a defect free surface for subsequent cold forging by rolling. Cold rolling is carried out to a degree of rolling of at least 80%, in this case 99.6% thickness reduction. The resulting nickel strip has a thickness of 80 μm and has a highly rolled texture. The annealing treatment is then performed at 550 ° C. for 30 minutes in a non-oxidizing gas atmosphere.

The result is a very sharp cube recrystallized texture, as can be seen in the strip according to FIG. 1. The amount of microcrystals with a cube state is 98% and the amount of incinerated crystal grains is 98% as well. The full width at half maximum of the (111) -pole intensity upon X-ray diffraction is FWHM = 4.4 °.

Example 2

Functionally pure nickel with a purity of 99.9 atom-% Ni is melted in a vacuum induction furnace under an alloy of 0.01 atom-% silver and transferred to the die cast. The ingot is rolled into a cube structure (22 × 22) mm 2 at 1000 ° C., uniformly annealed and metallized. Subsequently the cube material is cut and modified to obtain a defect free surface for subsequent cold forging by rolling. Cold rolling is carried out to a degree of rolling of at least 80%, in this case 99.6% thickness reduction. The resulting nickel strip is a highly rolled texture with a thickness of 80 μm. It is then annealed in a reduced gas atmosphere at 550 ° C. for 30 minutes.

The result is a nearly complete cube recrystallization assembly. The strip is subsequently exposed to the oxide for 5 minutes at 1150 ° C. in pure oxygen gas.

The nickel oxide layer generated has a cube texture, and 97% of the particles have a cube state. The texture is rotated 45 ° relative to the texture of the nickel strip (see FIG. 2). The half width of the (111) -pole is 6.2 °.

Example 3

Functionally pure nickel is melted under an alloy of 0.1-% silver and transferred to the die cast. The ingot is rolled into a cube structure (22 × 22) mm 2 at 1000 ° C., uniformly annealed and metallized. Subsequently the cube material is cut and modified to obtain a defect free surface for subsequent cold forging by rolling. Cold rolling is carried out with a rolling degree of 85% thickness reduction. The resulting nickel strip is 3 mm thick and subsequently annealed at 850 ° C. for 30 minutes for recrystallization. The surface is then cleaned and the strip is cold deformed to 80 μm thickness. Subsequently anneal in a reducing atmosphere at 850 ° C. for at least 45 minutes to form a cube texture.

Example 4

Functionally pure nickel powder is a powder metallurgical process by adding 4.0 atom-% tungsten powder and 0.1 atom-% silver powder. After pressing, tempering and hot forging a bar material of (12 × 12) mm 2 is obtained. The surface is cut and modified to obtain a defect free surface for subsequent cold forging by rolling. Cold rolling is carried out from a size of (10 × 10) mm 2 to a manufacturing size of 80 μm thick. The edge regions of the strip are separated and scattered. The resulting nickel strip is first annealed in a reduced gas atmosphere at 550 ° C. for 30 minutes for recrystallization. The strip is then second annealed in a reduced atmosphere at 1100 ° C. for 8 minutes to obtain a cube state that can be subjected to high thermal loads.

In Table 1, the values of substrates 5 and 6 show the positive action of the Ag additive according to the present invention on the FWHM (111) value, unlike the prior art (substrate 1-4).

Board

FWHM (111) value Recrystallization Recrystallization 550 ° C, 30 minutes 850 ° C, 30 minutes One Ni 8.3 - 2 Ni + 0.1 Atom% Mo 7.4 7.2 3 Ni + 0.1 Atom% W 8.8 8.6 4 Ni 7.9 6.8 5 Ni + 0.05 Atom% Ag 4.8 5.1 6 Ni + 0.01 Atom% Ag 4.4 5.3

Claims (6)

In a semifinished product of a nickel-based strip or flat wire having a cube recrystallization texture composed of pure Ni or Ni alloy, The pure Ni or Ni alloy comprises an Ag additive, the Ag additive is a nickel-based semi-finished product having a cube recrystallized texture, characterized in that 0.1 to 0.3 atomic-%. delete 2. The nickel-based semifinished product with a cube recrystallized texture according to claim 1, wherein a NiO layer of cube texture having a texture portion of 90% or more is provided to the semifinished product. First, a smelt metallurgy or powder metallurgy method including mechanical alloying forms a semifinished product composed of pure Ni or Ni alloys containing Ag additives up to 0.3 atomic-%, and then the semifinished product has a thickness of more than 80%. A process for producing a semifinished product according to claim 1, wherein the semifinished product is processed into strips or flat wires by hot forging comprising a subsequent cold forging of reduction, and finally the semifinished product is recrystallized annealed to achieve a cube texture. The method according to claim 4, wherein the semifinished product is heat-treated in an oxidizing atmosphere for epitaxial growth of the cube textured NiO layer after recrystallization annealing or during annealing. The nickel-based semifinished product with a cube recrystallization texture according to claim 1, which is used as a base for physicochemical coatings for the production of high temperature superconductors in the form of wires or strips.

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