CZ309351B6 - Alloy based on Fe-Al-Si-X and its use - Google Patents

Abstract

The Fe-Al-Si-X-based alloy with oxidation resistance at up to 1100 °C and mechanical and tribological resistance at least up to 750 °C contains a basic Fe-Al-Si alloy matrix with an Al content of 16 ± 4 by weight %, of 6 ± 4 by weight %, and at least one alloy element X of 4 ± 3 by weight % from the group of Zr, Cr, Nb, Ni, Ti, W, V and Mo, and the rest is Fe. The basic alloy matrix may also contain at least one additional alloy element Y from 0.01 to 1.5 by weight %, from the group of elements Zr, Cr, Nb, Ni, Ti, W, V, B and Sc, different from the element X. The alloy can be used as cast semi-finished products, in products from the group of forged semi-finished products, wire for welding and wire for hot spraying and in powder form.

Description

Alloy based on Fe-Al-Si-X and its use

Field of technology

The invention relates to an alloy based on Fe-Al-Si-X with oxidation resistance at temperatures up to 1100 °C and very good mechanical and tribological resistance up to at least 750 °C, especially for thermally and mechanically loaded components of internal combustion engines. It is a material capable of working with increased durability and abrasion resistance in specific conditions. It is a material capable of withstanding high temperatures and cyclic and thermal fatigue while maintaining very good tribological resistance. These are alloys containing iron with a significant proportion of aluminum with silicon and other elements that modify the properties and workability of the material. The expected main application use is for pairs of valves and valve seats in the heads of internal combustion engines, but the alloy will be able to be used in other areas as well, such as turbine components, brake equipment components, furnace components, etc.

Current state of the art

Currently, in an effort to reduce emissions released into the environment, materials based on austenitic steels, e.g. with a composition of 13%Ni, 13%Cr, 2.5 % W and 1.5 % Mn, or cobalt-based stellites, 17 to 32 % Cr, 2 to 16 % W, 0.1 to 2.5 % C, 3 to 22 % Ni, 1 to 8 % Mo and units of percent Fe and Si. Seats and valves are usually made of one piece of material, but often the functional surfaces are improved by welding or joining/welding several parts. It is similar for other types of components.

These alloys contain critical elements such as Cr, Ni and Co, which are expensive and can cause problems in the final material.

Existing alloys have a higher aluminum content, which reduces their toughness. The minimum silicon content can have a negative effect on high-temperature mechanical properties and thermal and oxidation resistance. Higher C content can cause weather damage. Mechanical properties, especially toughness, are relatively low, while their corrosion resistance at elevated temperatures is lower.

The essence of the invention

The above-mentioned shortcomings are largely eliminated by the Fe-Al-Si-X-based alloy with excellent oxidation resistance at temperatures up to 1100 °C and very good mechanical and tribological resistance at least up to 750 °C according to this invention. Its essence is that it contains a Fe-Al-Si alloy matrix with an AI content of 16 ± 4 mass. %, Si 6 ± 4 wt. %, and at least one alloy element X in the amount of 4 ± 3 mass. % which is selected from the group of Zr, Cr, Nb, Ni, Ti, W, V and Mo, and the rest is Fe.

The alloy in a preferred embodiment further contains at least one additional alloy element Y in the range from 0.01 to 1.5 mass. %, selected from the group of elements Zr, Cr, Nb, Ni, Ti, W, V, B and Sc, different from the element X.

Another essence of the invention is the use of an alloy in the form of a cast semi-finished product, a formed semi-finished product, a wire intended for welding, a wire intended for heat injection, powder using an atomizer or mechanical alloying.

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An advantageous solution involves the use of an alloy in the form of powders for 3D printing of metal materials, sintering and the creation of functional layers realized using coatings and cold or heat spraying, or for metal powder injection technologies.

The essence of the invention is a new material with a specifically defined mutual ratio of the average content of individual elements and a defined maximum and minimum content of individual alloying elements. The mutual ratio and defined range of the elements guarantees the heat strength and heat resistance of the material up to temperatures of around 1100 °C, and at the same time it also guarantees mechanical and tribological resistance at temperatures up to 750 °C even in environments containing S. The material can be used in cast and forged state, but given element ratios can also be applied in powder form and used for coatings, heat spraying, diffusion plating and for the production of parts using sintering and additive technologies. At the same time, the invention enables a complete replacement or significant reduction of the content of existing expensive and rare alloying elements such as Co, Cr, W, Ni, Mo, occurring in significant volumes in the materials used today.

Alloys according to the invention will enable the use of higher working temperatures, while maintaining or extending the life of the above components. The benefit is also a significant reduction in the content of critical alloying elements, especially those imported from outside the EU, which will be reflected in a reduction in the price of input raw materials, and therefore also in the price of the product. When compared to currently used high-temperature alloys, a weight saving of up to 25% of the components is possible due to the lower specific weight. Alloys are also characterized by higher corrosion resistance in aqueous environments. The reason is the formation of a passive layer made of aluminum oxide at a pH higher than about 3. At lower pH values, the passive layer is made of silica and also has a protective effect.

It is also possible to use recycled material as input raw materials for the preparation of alloys, e.g. engine blocks made of Al-Si alloys, even with a possible share of steel parts.

In contrast to the above-mentioned materials, in the proposed Fe-Al-Si-X and Fe-Al-Si-X-Y alloys, the above-mentioned critical elements, i.e. Cr, Ni, Co, are not represented either at all or in amounts of units of percent. At the same time, the useful properties of the proposed alloys are better or remain similar to those of commercially used alloys.

Compared to the pyroferal material, the proposed alloys have a lower aluminum content, which leads to higher toughness, and the increased silicon content compared to the pyroferal alloy (patent CS 115312 B5) has a positive effect on high-temperature mechanical properties and thermal and oxidation resistance. The proposed alloy has less C content so that weathering damage is avoided and this leads to product stability.

When comparing the proposed alloys and purely binary Fc^AI alloys or alloys of the same alloys, the proposed alloys show a significantly smaller grain size and thus better mechanical properties, especially higher toughness, but also higher corrosion resistance at elevated temperatures, especially oxidation.

Clarification of drawings

The alloy based on Fe-Al-Si-X according to the present invention will be described in more detail on concrete examples of implementation with the help of the attached drawings, where Fig. 1 shows the mechanical properties during the pressure test of the Fe-Al-Si5 alloy prepared by casting. Fig. 2 shows the oxidation resistance of the Fe-Al-Si5 alloy prepared by powder metallurgy in comparison with the Fe-Al binary alloy. Fig. 3 shows a semi-finished product for the production of a valve seat from the Fe-Al-Si alloy.

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Examples of implementation of the invention

The invention will be described in more detail in the following text with the help of specific examples, which are only illustrative and do not limit the scope of the invention in any way.

It is an alloy based on Fe-Al-Si-X with oxidation resistance at temperatures up to 1100 °C and mechanical and tribological resistance at least up to 750 °C, which contains an Fe-Al-Si alloy matrix with an Al content of 16 ± 4, Si 6 ± 4 mass. %, at least one alloy element X in the amount of 4 ± 3 mass. % which is selected from the group of Zr, Cr, Nb, Ni, Ti, W, V and Mo, and the rest is Fe.

In another case, it is an alloy, where the alloy matrix further contains at least one other alloy element in the range from 0.01 to 1.5 mass. %, selected from the group of elements Zr, Cr, Nb, Ni, Ti, W, V, B and Sc, which is different from the element in the previous alloy.

Example 1

Preparation of Fe-Al-Si5 alloy by casting: An alloy containing 16 ± 4 mass. % Al and 3 ± 2 wt. % Si was prepared by melting in a vacuum furnace. A copper mold was used for casting.

Example 2

The Fe-Al-Si5 alloy was prepared by mechanical alloying and plasma sintering. Oxidation resistance at 800 °C was tested and compared with Fe-Al binary alloy. The alloy with the addition of silicon achieves a significantly lower oxidation rate than the reference Fe-Al binary alloy.

Example 3

The Fe-Al-Si5 alloy was prepared by mechanical alloying and sintering in plasma and on a heat-treated material, the production of a valve seat was tested with the help of electric spark machining, see the semi-finished product in Fig. 3.

Example 4

Powder produced by atomization from the base alloy Fe, Al 16 ± 4, Si 6 ± 2 mass. %, supplemented by element X, which is Ti in an amount of 2 ± 1 mass. %, and by element Y, which in this case is B in an amount of 0.6 ± 0.2 mass. %. The powder is used for heat spraying using plasma or the HVOF method and to create a functional layer with significantly increased tribological resistance up to temperatures of 700 °C. An example of use is, for example, with brake discs within the framework of the creation of a compact layer and a composite spray distribution.

Example 5

Powder produced by grinding from the base alloy Fe, Al 16 ± 4, Si 6 ± 2 mass. %, supplemented by element X, which is W in the amount of 1 ± 0.5 mass. %, and by element Y, which is Nb in the amount of 0.4 ± 0.15 mass. %. The powder is used for 3D printing using the SLS method, for example for the production of shaped inserts in molds for injection using the MIM and CIM methods. The insert created in this way has increased temperature and abrasion resistance against ceramic and metal particles injected by the MIM and CIM methods.

Example 6

Powder produced by grinding from the base alloy Fe, Al 16 ± 4, Si 3 ± 2 mass. %, supplemented by element X, which is Mo in an amount of 1.5 ± 0.5 mass. %, and by element Y, which is V in the amount of 0.3 ±0.1 mass. %. The powder is used for 3D printing using the SLM method, for example for the production of components that can be used in the energy sector. In this case, it is specifically a house for the distribution of steam

-3 CZ 309351 B6 located before the first stage of the steam turbine. The part created in this way has sufficient corrosion and abrasion resistance at temperatures up to 580 °C, as well as long-term temperature stability.

Example 7

Powder produced by grinding from the base alloy Fe, AI 16 ± 4, Si 3 ± 2 mass. %, supplemented by element X, which is Zr in an amount of 1.2 ± 0.5 mass. %. The powder is used for laser welding of functional contact surfaces on parts of welding fixtures intended for large-scale production of automotive components. The layers formed in this way have approximately 1.2 times greater abrasion resistance than parts with nitrided or cemented surfaces.

Example 8

Arc welding wire made by casting and subsequent forming from a base alloy of Fe, AI 16 ± 4, Si 3 ± 2 mass. %, supplemented by element X, which is Cr in an amount of 2 ± 0.5 mass. %, and by element Y, which is Ti in the amount of 1 ± 0.4 mass. %. The wire is used for the renovation of worn valves and valves in the primary circuit and in steam superheaters.

Industrial applicability

The alloy according to this invention is intended for products intended mainly for two industrial segments, namely for high-temperature applications up to 1100 °C, which include, for example, furnace components such as bearing parts, refractory partitions, grates, muffles, resistance heating elements, etc., and also high-temperature pipes, burner nozzles, slide valves and valves, and also for products designed for applications with very good mechanical and tribological resistance, at least up to a temperature of 750 °C. Examples include components of internal combustion engines and turbochargers, components of combustion, steam, gas and steam turbines, or components of braking devices such as discs, brake segments, etc.

Claims (6)

PATENT CLAIMS 1. Alloy based on Fe-Al-Si-X with oxidation resistance at temperatures up to 1100 °C and mechanical and tribological resistance at least up to 750 °C, characterized by the fact that it contains an Fe-Al-Si alloy matrix with AI 16 content ± 4% by weight, Si 6 ± 4% by weight, and at least one alloying element X in an amount of 4 ± 3% by weight, which is selected from the group of Zr, Cr, Nb, Ni, Ti, W, V and Mo, and the rest is Fe. 2. The alloy according to claim 1 or 2, characterized in that it further contains at least one additional alloy element Y in the range of 0.01 to 1.5 wt.%, selected from the group of elements Zr, Cr, Nb, Ni, Ti, W, V, B and Sc, different from the X element. 3. Use of the alloy according to claim 1 or 2 for cast semi-finished products. 4. Use of the alloy according to claim 1 or 2 for products selected from the group of formed semi-finished products, wire intended for welding and wire intended for heat spraying. 5. Use of the alloy according to claim 1 or 2 for the production of powder. 6. Use of the alloy according to claim 5 in the form of powders for 3D printing of metal materials, sintering and the creation of functional layers realized by means of coatings and cold or heat spraying, or for metal powder injection technologies.