RU2311262C1 - Method for manufacturing porous-fibrous metallic material - Google Patents

Abstract

FIELD: manufacture of porous materials from metallic fibers, namely processes for producing fibrous metallic materials of high porosity from heat resistant alloys for sound absorbing structures of hot tract of gas turbine engine, other structures with high demands to their strength and heat resistance such as high temperature filters, vibration insulation materials and so on.

SUBSTANCE: method for making fibrous metallic materials with porosity up to 95% for gas turbine engines operating at 450-600°C comprises steps of preliminarily forming metallic mat of fibrous mass including metallic fibers with length no less than 100 mm due to needle punching of them with closeness 0.5 x 10⁴ - 1 x 10⁴ m ^-2. Diameter of metallic fibers of heat resistant metals or alloys is in range 15 - 30 micrometers. Prepared metallic mat is subjected to sintering in container having limiting members in vacuum or protection atmosphere at temperature consisting 0.75 - 0.85 of material melting temperature.

EFFECT: enhanced strength, heat resistance and sound absorbing efficiency.

4 cl, 1 tbl, 4 ex

Description

The invention relates to methods for producing porous materials from metal fibers, and in particular to methods for producing fibrous metal materials with high porosity (up to 95%) from heat-resistant alloys for sound-absorbing structures (GPC) of a hot path of a gas turbine engine (GTE) at operating temperatures of 450-600 ° C, which can also be used for the manufacture of other structures with high requirements for their strength and heat resistance, such as high-temperature filters, vibration insulation materials, etc.

Porous metallic materials have been known for a long time and due to the combination of their properties (high porosity with a sufficiently high strength and flexibility) find their application in various fields of technology.

Porous fibrous metal materials are most suitable for creating high-temperature ZPK. They have effective absorption properties that are practically independent of the sound pressure level and provide noise reduction over a wide frequency range. Such materials have high characteristics of temperature resistance, fire safety, mushroom resistance and little absorb various liquids.

To date, several methods for producing porous fibrous metal materials are known. All of them have a number of disadvantages and limitations of use.

A known method of obtaining a porous metal material, comprising making a suspension of fibers in a liquid medium, followed by deposition of the suspension on a vibrating perforated base or by introducing the suspension into a mold with porous walls. After draining the liquid, a sheet or article of a given shape is obtained, which is then pressed and sintered into a low-density material (US Pat. No. 3,127,668).

The disadvantages of this method are the low porosity of the materials obtained and the difficulty of preparing a suspension of long metal fibers in a liquid medium. In addition, particles of the liquid or products of its reaction with metal fibers remain on the surface of the fibers, which adversely affects further sintering.

A known method of obtaining a porous metal material from thin metal fibers by air layering and subsequent mechanical bonding or pressing of a porous structure (US patent No. 3.469.297).

The disadvantages of this method are the absence of a sintering process and a small cross-section of the fibers (the best results when using this technology with a fiber thickness of 4 μm), which reduces the strength when obtaining material with high porosity.

A known method of manufacturing a reinforced non-woven metal material by processing a mass of free metal threads using conventional equipment of the textile industry to obtain a fabric of metal threads and the application of several such paintings to one another to obtain a multilayer structure. A reinforcing substrate is placed between the webs, as a result of which a reinforced non-woven metal sheet material with high strength and durability is formed (US Pat. No. 5,972,814).

The disadvantages of this method are the use of a reinforcing substrate, which reduces the overall porosity of the fibrous material and the need to use metal fibers with an uneven cross-section (rough surface) for bonding between the individual fibers.

The prototype adopted a method of obtaining porous-fibrous metal materials with a uniform structure, including the preliminary formation of a metal mat from the pulp and its further sintering. The formation of a metal mat is carried out by sieving the crushed metal fibers on a substrate with the formation of one or more layers. In this case, each layer is coated with adhesive or a binder, after which a subsequent layer is applied to it, etc. until the mat is of the required thickness. Then the mat is dried, subjected to sintering and, if necessary, pressing (US patent No. 3,811.976).

The disadvantages of the prototype method:

- despite the possibility of obtaining a porous-fibrous metal material with high porosity, the known method does not provide high performance properties of this material at an operating temperature of 450-600 ° C in the conditions of a hot gas turbine engine;

- this method does not provide a porous material from long metal fibers;

- in the prototype method in the manufacture of a porous metal material, a binder is used, which does not exclude the presence of its residues or products of its reaction before sintering.

The technical task of this invention is to develop a method of manufacturing a porous fibrous metal material from long metal fibers (from 100 mm), with high strength and heat resistance, operable at temperatures of 450-600 ° C in the conditions of the hot gas turbine engine, with low specific gravity and high porosity (up to 95%) with high acoustic efficiency; without the use of various binders, liquids, and other additional materials in the manufacturing process of such material, the presence of which adversely affects the properties of the porous-fibrous metal material.

To solve this problem, a method for producing a porous-fibrous metal material is proposed, including the preliminary formation of a metal mat from pulp and its further sintering, characterized in that the metal mat is formed by needle-piercing a pulp consisting of metal fibers with a length of at least 100 mm and a density punching 0.5 × 10 ⁴ -1 × 10 ⁴ m ^-2 .

As the starting material, long metal fibers with a diameter of preferably from 15 to 30 μm obtained by melt extraction or deformation can be used.

Sintering is carried out in a vacuum or protective atmosphere at a temperature of 0.75-0.85 of the melting temperature of the material, which allows to obtain sufficient strength at the points of contact of the fibers.

Sintering is carried out in containers with dimensions corresponding to the geometric parameters of the porous fibrous material, under load, using metal or ceramic mandrel limiters, which provide the required height of the porous fibrous material during sintering.

As the material of the fibers can be used metals or alloys with high heat-resistant properties, for example, based on iron or nickel.

The proposed method for producing porous fibrous metal materials by needle-punching a pulp with a punching density of 0.5 × 10 ⁴ -1 × 10 ⁴ m ^-2 followed by sintering of the metal mat allows to obtain materials from long metal fibers with a given porosity, with high acoustic efficiency as applied for example, to aircraft turbojet engines, characterized by a fairly uniform absorption spectrum at frequencies above 1.6 kHz with an efficiency of about 6-8 dB in conditions close to uyuschim in GTE.

The selected length of the fibers and the density of penetration of the pulp provide sufficient strength and plastic characteristics of the material with its high porosity and high sound-absorbing properties. When the penetration density is less than 0.5 × 10 ⁴ m ^{-2, the} porosity of the fibrous material does not increase, but its strength decreases. When needle-piercing with a density of more than 1 × 10 ⁴ m ^{-2 the} porosity of the finished porous-fibrous metal material does not exceed 90%, while its strength increases slightly.

Examples of implementation

Example No. 1

An X20H80 grade alloy wire (T _pl = 1400 ° C) with a length of 100 mm and a diameter of 30 μm was used as a starting material.

The formation of pulp was carried out on the installation to obtain a fibrous layer with a uniform distribution of the density of metal fibers in volume.

Needle piercing was performed on a fiber bonding unit with a moving needle table with punching needles at a piercing density of 0.5 × 10 ⁴ m ^-2 .

As a result of needle punching, a nonwoven mat with a porosity of 98% was obtained.

Sintering was carried out in a container with metal stops under load at a vacuum of 10 ^-4 mm Hg. and a temperature of 1150 ° C for 2.5 hours. The height of the limiters was selected based on the specified parameters of the porous material.

As a result, a porous fibrous metal material with a porosity of 95% was obtained.

Example No. 2

Metal fibers from an alloy of the brand X20H80 with a diameter of 15-20 μm, a length of 150 mm, obtained by extraction of a hanging drop of melt, were felted in a pulp formation unit. The resulting mass was punched with needles with a piercing density of 1 × 10 ⁴ m ^-2 . The resulting non-woven mat with a porosity of 96% was sintered in a container under load with metal stops at a vacuum of 10 ^-4 mm Hg. and a temperature of 1100 ° C for 2.5 hours.

As a result, a porous fibrous metal material with a porosity of 85% was obtained.

Example No. 3

Metal fibers from an alloy of the grade 12X18H9T (T _pl = 1450 ° C) with a diameter of 15 μm and a length of 300 mm after felting were punched with needles with a piercing density of 0.8 × 10 ^-4 m ^-2 . The resulting non-woven mat with a porosity of 97% was sintered in a container under load with metal stops at a vacuum of 10 ^-4 mm Hg. and a temperature of 1200 ° C for 3 hours.

As a result, a porous fibrous metal material with a porosity of 85% was obtained.

Example No. 4

According to the known method (prototype), a porous fibrous metal material was made from fibers of an alloy of the brand X20H80 with a diameter of 50 μm, a length of 5-10 mm, which is a fiber mat with a porosity of 85%.

Comparative results of studies of samples of materials manufactured by the proposed method and prototype are presented in table 1, where examples 1-3 are the proposed method, example 4 is the prototype.

The table shows that the materials manufactured by the proposed method have a porosity of up to 95%, large values of sound absorption coefficient, heat-resistant and significantly superior to the material made by the prototype method, in terms of strength.

In addition, the use in the proposed method of long metal fibers in the manufacture of a porous material for high-temperature ZPK aircraft engine can reduce the gradual destruction of porous-fibrous metal materials under the action of high-intensity sound.

The resulting material can be machined and calibrated in a press to the required dimensions while maintaining a uniform structure.

Thus, the application of the proposed method allows to obtain porous fibrous metal materials from long fibers with high strength and heat resistance, with low specific gravity, porosity up to 95%, with high acoustic efficiency, operable at a temperature of 450-600 ° C.

The proposed method is more economical, eliminates the pressing process and the use of various binders.

Sound-absorbing structures made of the obtained porous-fibrous materials have high performance characteristics required for new generation products.

Table 1 Example No. Fiber material Porosity,% Heat resistance (at a temperature of 600 ° C, holding time of 100 hours),% Sound absorption coefficient, α σ _B , kg / cm Acoustic efficiency, dB one X20H80 95 1.89 one 150 6-8 2 X20H80 85 1,52 0.9 280 6-8 3 12X18H9T 85 2.00 0.9 300 6-8 four X20H80 85 2.01 0.7 fifty collapsed during the test

Claims (4)

1. A method of obtaining a porous fibrous metal material, including the preliminary formation of a metal mat from the pulp and its further sintering, characterized in that the metal mat is formed from a fibrous mass consisting of metal fibers with a length of at least 100 mm, by needle piercing with a penetration density of 0 , 5 × 10 ⁴ -1 × 10 ⁴ m ^-2 . 2. The method according to claim 1, characterized in that the diameter of the metal fibers is 15-30 microns. 3. The method according to claim 1, characterized in that the metal fibers are made of heat-resistant metals or alloys. 4. The method according to claim 1, characterized in that the sintering of the metal mat of the required height is carried out in vacuum or in a protective atmosphere at a temperature of 0.75-0.85 of the melting temperature of the material in the container with limiters.