DE7609579U1 - WORKPIECE CONSISTING OF AT LEAST TWO COMMON METALLIC CONTACT SURFACES - Google Patents

Description

The subject of the innovation is at least one out two common metallic contact surfaces comprising individual parts of an existing workpiece, tool or object of daily use, intended for use in an inert atmosphere and made of a nickel-containing one Alloy.

Adhesion, friction and wear, touching, Metal parts at rest as well as in reciprocal sliding or ron motion take πόγτγ. «! with increasing temperature. The difficulties this poses can be portable Limits are kept as long as the ambient atmosphere Contains oxygen or this together with water vapor and the partner materials made of high-temperature, stable, oxide-forming alloys exist. These oxidic surface layers prevent intimate metallic contact. It is true that here, too, occur at the touching surface tips very high specific surface pressures even under relatively small loads, so that the surface tips become plastically deformed.

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The protective oxide films break through and it localized welds occur. During the gliding process, however, these welding bridges become · ■ -sheared off. The broken metallic surface areas are chemically highly active and immediately cover themselves again in an oxidizing ambient atmosphere a new protective oxide film.

However, this healing process cannot take place if the friction partners are in a vacuum or in an inert atmosphere. The poles of it are very high coefficients of friction before, - ίΐ, ^ Ι and a rapid Zer- ^,! disturbance of the surfaces, associated with high wear. [ If the two resting bodies move over,; If this is not the case for a longer period of time, then in extensive surface areas: cL-areh Or ⁺ * ¹ 1 «Vvp. Welding, alloying can occur. The adhesive forces can become so great that they die Achieve strength of the material itself.

This problem is of particular importance in connection with the development of He gas turbines and Ee-cooled high-temperature reactors , which is, for example, caused by cutting ahead; len wear and failure of bearings, due to the warping and tearing of parts, including pipes, which are in the _; The occurrence of temperature gradients are no longer able to move freely, due to diffusion welding of visual connections, splashing, blade attachments or noticeable

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"makes cash.

It was therefore the object to provide these workpieces, work equipment and utensils with a diffusion barrier for ^l in saueretofffreier inert preference as helium-atmosphere through which the disadvantages, especially so Duffionsverschweißungen the interfaces avoided v / ground.

It has now been found that such a diffusion barrier arises when eire between the netall contact surfaces film-like layer of finely divided, hexagonally crystallized boron nitride is arranged. The figure shows neighboring Metal parts 1 and 2, between which a layer 3, containing boron nitride, is arranged as a diffusion barrier is.

This layer is produced by a separating agent from a paste-like, spatula-able, spreadable or liquid-sprayable suspension, the $ 5 - $ 50, preferably 15 - 40 io hexagonally crystallized boron nitride, 0.5 io - 30 i » binder, 2 io - 6 $ swelling agent and 50 F -. 95 io liquid optionally contains corrosion inhibitors containing one- or multi-component suspending medium.

This release agent is applied to the boundary surfaces, followed by forming a protective film, the at temperatures Võti 100 ⁰ C - 500 ⁰ C for 0.25 - is baked for 3 hours.

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In this case, this suspension is expediently applied to adjacent metal parts which are made of a nickel-alloyed material Alloy with smooth interfaces are made and connected to each other by fasteners or sliding against one another, for example in a thermally elastic manner Suspension or are arranged in sheet metal stacks.

The use of boron nitride as a lubricant, as a poor shield and to prevent sticking together of glass beads is known from DT-AS 1 104 930, DT-AS 1 102 710 and DT-OS 1 667 696, for example. Also knows one preparations of boron nitride with binders by DT-AS 1 467 050 and DT-PS 282 748.

But with these uses, the problem set out above kane Solle, according to which in inert Atmosphere Welding of adjacent metal parts can take place, which must be prevented. It is surprising that in such cases an arrangement of boron nitride between the interfaces acts as a diffusion barrier.

It has been found that the strong Adhäsionsvers described welds avoided, and the friction and wear can be effectively reduced if at least one of the two has an ¥ lax! effect

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Solid body covered at the point of contact with a thin protective layer containing hexagonal boron nitride will. The protective layer fulfills the following important requirements:

■ It acts as a diffusion barrier and prevents

! ... so the metallic contact of the touching ones

j body.

■ It does not diffuse into the carrier material and

can therefore also over long holding times at high

Do not move temperature.

It has excellent sliding properties.

It is chemically stable and therefore does not form any decomposition products.

It is in a very wide temperature range effective.

It is also stable in an oxidizing atmosphere and at temperatures up to 14-00 ⁰ C, so that its protective effect is not endangered by any strong contamination in a He atmosphere - e.g. water vapor breakdown,

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It has a high thermal conductivity, so \ 7 . that no heat transfer problems occur.

It has a high thermal shock resistance The advantage of inflation can be seen from the following:

Two pairs of splashbacks made of a highly heat-resistant Pe-Cr-Ni turbine material are examined for comparison. Paddling pair no. 1 is untreated. The contact surface of a flange of the paddling pair Ur. 2 is treated with an aqueous suspension containing 30% by weight of hexagonal boron nitride, 4% by weight of sodium metaborate as the inorganic binder and 3% by weight of carboxymethyl cellulose as the swelling agent, so that a thin, uniform protective film is formed. The layer is baked ^{in air at 40O 0} G for 1/2 hour.

Both pairs of paddles are screwed together with bolts, with the thread of the bolts also being used beforehand were coated with the protective film described and with an average surface pressure of 50 kp / cm pressed together. After heat treatment of

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100 Il "at 75O ⁰ C in pure helium, with a water vapor and oxygen content each below 5 ppm, it tries to separate the Planschpaare again, whereby the following results are obtained:

All screw connections can be easily loosened.

Flange pair Ur. 2 shows no adhesion whatsoever -jjaxL can can be separated undamaged and effortlessly.

Paddling pair ITr. 1 is so tightly welded that it is

cannot be separated by tensile forces of 200 kp / cm.

In another experiment, 10 housing screws were-Cr-Co Ni-Iegierung treated from a high temperature-resistant with a paste, the $> an organic binder, acrylic-based in an organic! Solvent consists of 25 wt. 56 hexagonal boron nitride and 10 wt.. Only the threaded bolt was dealt with. Before screwing, the lacquer was ^{baked at 120 °} C. for 2 hours. The screw connections were tightened with a torque of 4 mkp. In addition, an equal number of untreated screw connections made of the same material were also screwed together with 4 mkp. · '

After heat treatment of all fittings for 100 hours at 75O ⁰ C in pure helium could all, 7,609,579 10/28/76 """

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Screw connections treated with the paste containing boron nitride can be loosened with a torque of 1 to 3 mkp, whereas the untreated screw connections are diffusion-welded and could no longer be loosened or were torn off when applying too high a torque the .

The innovation also relates to pipelines that carry hot gases such as helium. Step here

Relative movements in the sheet metal stacks and metal mats forming the insulation due to temperature changes. If there is no longer free mobility due to local diffusion welds, distortions occur that can destroy the insulation or at least greatly reduce its insulating effect.

When using the innovation "make here besides the Separating effect the good sliding properties of the hexagonal Boron nitride advantageously noticeable.

With regard to the application of the release agent containing hexagonal boron nitride, there is a choice between one aqueous and an organic suspension, preferably the aqueous suspension is to be used because by the presence of a suitable swelling agent: it has certain thixotropic properties, i.e. that it is relatively easy to deform, but takes on a relatively high apparent viscosity immediately after application, which counteracts any too rapid spreading and draining before drying. The organic suspension is applicable in cases where the presence of a

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mineral binder has a disruptive effect, i.e. in the Cases where, after thermal treatment, pure, unbound boron nitride remains as a dry lubricant target.

In an aqueous suspension, boron nitride is the proportion of the binder is lower, et- ^r a select of 0.5% "$ to 2.5. It is desirable that as a swelling agent which Hatriumsalz of the carboxymethyl cellulose in the range of 2 fo fo Ms 6 , preferably from 3 _£>} to use. As a corrosion inhibitor may be added to about 0.5 i- ITatriumnitrit.

In the case of an organic boron nitride suspension, the proportion of binder will generally be higher, depending on the desired consistency about 6 to 15 $> (for compounds that can be troweled, the upper values, even up to 30 ? <>). The same .Stoff (polymer compound) can occur both as a binder and as a swelling agent (increase in viscosity) in the suspension. The rest is a mixture of organic solvents.

With regard to the release agent components, it can be said that that 'in aqueous suspensions, sodium phosphate is used as a binder, sodium carbonate, sodium metasilicate and sodium metaborate can be used. With regard to

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Sodium metaborate is particularly suitable for the suspended boron nitride.

Commercially available sodium salt of carboxymethyl cellulose can be used as the swelling agent, but others can also be used Commercially available swelling agents are suitable.

In the case of organic suspensions, polymethyl methacrylate is particularly suitable as a binding and swelling agent Has the property of volatilizing at higher temperatures without residue or extensive decomposition. Other Polymers, e.g. polystyrene, can also be used.

As such suspending media are on the one hand to use, which dissolve the polymeric binder, una the other hand, allow a progressive drying, with the following Zusa mm ensetzung is exemplary low '

40 tfo methylene chloride,

$ 30>acetone,;

20 ia methyl ethyl ketone,

10 ^ toluene.

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Claims (1)

LABORATOIRE SUISSE DE RECHERCHES HORLOtfÄREÜ NEUCHATEL / SUISSE GUTEHOEPNUNGSHÜTTE STERKRADE
Corporation PA-Dr. Ho / Ri 4200 Oberhausen 11, June 18, 1976 File number: G 76 09 579-9 i ——_— - ———_———— ι Protection claim: j [From at least two common metallic | Individual parts having touching surfaces Workpiece *} Tool switch or commodity that is used for Is intended for use in an inert atmosphere and consists of an alloy containing nickel, characterized, that in the area of the contact surfaces between the individual parts a film-like separating layer is arranged, which contains hexagonally crystallized, finely divided boron nitride. 7609579 28.18.76