DE1260279B - Process for the production of a ductile diffusion connection between heat-resistant alloys - Google Patents

Description

Process for producing a ductile diffusion connection between Creep Resistant Alloys The invention relates to a method of manufacturing a ductile connection between heat-resistant alloys. Since the inventive Process is characterized by a diffusion in the solid state or the connection between the metallic parts through a special diffusion process comes, such a connection is referred to below as a diffusion connection.

Refractory alloys are currently commonly used with relative low-melting, nickel-based brazing alloys. These nickel alloys, which melt at temperatures between 1000 and 1200 ° C, are indeed for the production simple connections are suitable, but they are not sufficient in those cases in which higher demands are placed on the toughness and strength of the connections. The hard solders have their own hardness and brittleness, and those with Compounds made from them tend to have the same or similar properties to accept. Compounds that are more hard and brittle than the base metal have, but affect the durability and usability of the through them created constructions.

The prior art also includes making connections which, through suitable measures, produce a eutectic, i.e. a liquid phase is exploited. The magazine "Materials in Design Engineering", Vol. 51, Born in 1960, April issue, p. 14 to 16, it can be seen that parts of a heat-resistant Let the zirconium alloy bond by means of nickel by annealing above it made the eutectic temperature and then brought about a post-diffusion will.

The procedure is also based on a bond via a eutectic phase directed according to the German patent application G 4681 VI a / 49h: For cohesive Connection between iron parts are the surfaces to be welded with a Soot layer covered and then heated, with a formation of low-melting on the surface Iron carbides enter and diffuse in in the further course of the annealing treatment takes place inside the base metal. It also becomes a material connection For non-ferrous metal parts, the first aim was to form a low-melting alloy and then made a post-diffusion; for this purpose, phosphorus has proven to be a suitable substance Material proven.

According to French Patent 1196 554, phosphorus can be used as Also use eutectic formers to create a compound with iron. Distinctive Measure of this method for joining heat-resistant metallic objects is always the initially desired formation of a eutectic, i.e. a liquid Phase. Therefore, the annealing temperature for making the connection is also in each case higher than the eutectic temperature. By taking advantage of a eutectic phase Although connections can be made at relatively low temperatures, in the eutectically melted area of the connection, however, there remains a zone in which the ductility is lower than in the base metal. Also through a subsequent After diffusion, the mechanical-technological properties of this connection area, primarily its toughness and deformability, do not improve sufficiently.

The invention is based on the stated disadvantages to fix, in particular those connections are avoided that are under exploitation a eutectic or other liquid phase can be produced.

The invention uses the property to solve the problem some chemical elements made to diffuse very quickly. These elements are Used individually or in combination as a means to create a reliable between heat-resistant parts Establish a diffusion bond of great strength.

According to the method according to the invention is to connect structural parts, the one den Composition corresponding to heat-resistant alloys have to ensure that on the surfaces to be connected by diffusion at least one element from the group consisting of boron, carbon and silicon is present. In particular, according to the method according to the invention, a relatively thin, from a homogeneous, d. H. single-phase alloy existing sheet metal used in which at least one very rapidly diffusing element from the group consisting of boron and carbon and silicon present as a small but essential component of the alloy is.

The diffusion connections achieved by the method according to the invention retain their strength even at higher temperatures.

The inventive method for producing a ductile diffusion connection high strength between parts made of heat-resistant alloys to not molten path is characterized in that between the provided to be connected surfaces of the parts to be connected at least one of the because of their small atomic diameter easily diffusing chemical elements from the group Boron, carbon and silicon is introduced and the parts so arranged in close contact with each other to at least 900 ° C for a period of at least 20 seconds until a strong metallic diffusion in the solid state Binding of the parts is achieved.

The process can expediently be carried out in the following way: The surfaces of the parts of the heat-resistant alloys to be connected become flush superimposed. A thin sheet is placed between these surfaces to be connected pushed. This thin sheet consists of an alloy that contains at least one the elements boron, carbon or silicon has. The arrangement is in protective gas heated to at least 900 ° C for at least 20 seconds. The temperature can be up to to 1250 ° C and the annealing time is 1 hour or more depending on the composition the parts to be connected. The fast diffusing element or elements that are present in the intermediate sheet, diffuse quickly into the adjacent adhesive surfaces the metallic parts to be connected. This rapid "diffusion ahead" accelerates now also the diffusion of the more inert basic elements of the metallic elements to be connected Parts. This creates a metallic bond and it becomes a connecting zone Great strength created the small amounts of the rapidly diffusing elements contains. The junction is therefore usually due to a grain growth over the adhesive surfaces of the two metallic construction parts are marked.

It has been found to be useful in the diffusion bonding process proved that the rapidly diffusing elements are in the form of a homogeneous alloy are used, in addition to at least 0.1% of boron, carbon and / or silicon consists of iron, cobalt, nickel, chromium and / or manganese as the base metals.

The diffusion bonding method of this invention can be applied to nickel, Cobalt and iron based alloys are used. The alloys can one or more components of titanium, molybdenum, chromium, manganese, aluminum, vanadium and tungsten in substantial proportions. Pure nickel, iron and cobalt can be joined as well as their alloys.

It was found that the very rapidly diffusing elements carbon, Silicon and boron, necessary for the production of a diffusion connection according to the invention are suitable, have certain critical properties. The elements should be with a very high speed into the structure of the base metals to be joined diffuse in. While now all metallic elements are capable of being in the solid To diffuse state, those elements that are of interest here have one very high speed of diffusion. The elements carbon, silicon and Boron are referred to below as highly diffusible elements. Elements with small atomic radii diffuse very quickly in a wide variety of metals. These highly diffusible elements also exhibit significant solubility in the base metal or in the base metals to be joined. On the adhesive surfaces as a result, mixed crystal formation takes place, and indeed faster than the formation more brittle intermetallic compounds. The highly diffusible elements also have a certain solubility in the various metals; the then too thin intermediate sheets can be processed.

The carbon atom has a very small atomic radius (0.77 Å) and diffuses very quickly into the base metals. Carbon also has one noticeable solubility in various elements, e.g. B. in cobalt, iron, Manganese, nickel and titanium. Through the diffusion of carbon into these elements or alloys of these elements become mixed crystals or homogeneous alloys formed with carbon.

The carbon can be applied to the surfaces to be connected in different ways Way to be applied. One or both of the parts to be connected will be attached to their Carburized adhesive surfaces. At the diffusion temperature, the carbon dissolves in the structure of the materials and diffuses across the connecting surfaces, whereby the bond is promoted. Carbon can also be precipitated by adding a suspension of carbon in a neutral liquid to the brings surfaces to be connected. As stated above, is carbon soluble in a number of elements. The necessary carbon concentration for production The diffusion bond can also be obtained by making thin, carbon brings alloyed sheets between the adhesive surfaces.

The silicon atom has a relatively small atomic radius (1.17 Å) and is able to diffuse rapidly in certain base metals. Silicon has a substantial solubility in various elements between room temperature and diffusion temperature on. It can therefore also be used here to produce the diffusion connection according to the invention thin sheet metal alloyed with silicon is produced between the adhesive surfaces the parts to be connected are to be accommodated.

The boron atom is also relatively small (0.97A) and is known to diffuse rapidly in various high temperature alloys. Boron is also soluble in a number of elements so that alloys can be made therefrom to provide a diffusion bond according to the invention. The thin intermediate sheet to be used for the diffusion connection to be produced according to the invention contains at least one of the elements carbon, boron and silicon in an amount of at least 0.10 / 0. As a practical matter, it is desirable to have at least 0.2% carbon, boron or silicon, or a combination of two or more of these elements. Larger proportions z. B. up to 10% can be present in these sheets. The maximum of the sum is determined by the base metal in which the carbon, silicon or boron are present, since their solubility in this base metal will vary.

The diffusion element can be in a thin sheet of such a binding alloy be included. The binding alloy can, however, also be in another form, so z. B. in powder form, in braided wires, wire nets and the like harder to perform and less controllable this way can be purer Carbon, silicon or boron also in powder form in a neutral liquid suspended and brushed onto the surfaces to be connected. As above mentioned, intermediate plates have proven satisfactory in use.

About the influence of carbon as a rapidly diffusing element To be enumerated in a diffusion bond alloy, a nickel-carbon alloy became manufactured. At temperatures from 1000 to 1300 ° C, carbon in nickel is between 0.23 and 0.65 percent by weight soluble. However, a practical area of Set 0.2 to 0.7 percent by weight carbon. Exceeding the solubility limit of carbon in nickel by small amounts is not a major disadvantage. One Nickel-carbon alloy, which contains 0.35 percent carbon by weight, was made manufactured and processed to a thickness of 0.076 to 0.101 mm. This alloy is hereinafter referred to as "alloy 2406". In the adjacent table I will look at the composition of various high-temperature alloys to which the Method according to the invention was applied, described.

The alloy AISI 347, alloy D, alloy I and alloy H of Table I, which were in the form of strips, were polished and degreased and then connected by diffusion according to the invention with a strip of alloy 2406, the strip between the surfaces to be connected Sample was brought. The joint was a simple overlap that was the same length as the thickness of the base metal. The connection was made in a vacuum of 0.05 to 0.07 microns. While the bond was being formed, no pressure was applied to promote the bond. However, the application of pressure would secure the contact for making the diffusion bond and can be used in special circumstances. In some cases initial melting occurs and the small amount of molten alloys provides good contact for the solid state diffusion process. The various temperatures and times used are described in Table 1I. Table 1I also contains the greatest shear strength of the samples tested at room temperature. Table 1I Production of the diffusion compound according to the invention using various base metals and a nickel-carbon alloy 2406 (nickel with 0.35 percent by weight carbon) as an intermediate sheet L1d. No. Base metal Diffusion temperature Diffusion time Greatest shear strength ° C Minutes kg / mm2 24 AISI347 1225 10 15.1 25 AISI347 1225 10 25.7 35 alloy D 1125 10 25.8 36 alloy D 1225 10 23.9 28 alloy 1 1150 10 37.9 48 alloy H 1225 10 28.4 The test results in Table II show particularly clearly that nickel-carbon alloys can be used according to the invention in order to create joints with excellent strength. Furthermore, nickel-based alloys containing 0.20-0.70% carbon can be used to diffuse a variety of high temperature alloys. In these alloys, the carbon remains in solid solution with the nickel at working temperatures and therefore enables the production of thin strips from these alloys. If such strips are placed between the adhesive surfaces of the base alloys to be joined and heating takes place up to the diffusion temperature, the carbon dissolved in the nickel diffuses into the adhesive surfaces of the base alloy and thus promotes diffusion formation. The direct contact of the adhesive surfaces can be supported by pressure, but is not necessary for a diffusion connection if the adhesive surfaces are flat and are in close contact with one another. Instead of the nickel-carbon alloy, other carbon-containing alloys can also be used as the intermediate sheet. These alloys can contain base metals such as B. cobalt, iron, manganese and titanium, all of which have some solubility for carbon at the diffusion bond temperatures between 900 and Table HI Diffusion diffusion time Greatest Sample base metal alloy of the intermediate plate temperature shear strength ° C minutes kg / mm2 1 alloy PH 2759 (0.75 percent by weight boron, 1140 to 1250 5 19.0 Remainder cobalt) 2 Alloy PH 2760 (1.50 percent by weight 1145 to 1225 5 13.4 Silicon, remainder nickel) 3 Alloy N 2759 1145 to 1170 5 39.6 4 Alloy N 2760 1150 to 1200 5 28.1 The traps in the test pieces discussed in the table above were created by a simple overlap, the overlap roughly corresponding to the thickness of the base metal whose parts were connected to one another. No pressure was applied. The surface contact only came about due to the weight of the upper part.

The strength achieved by these compounds with silicon and boron as highly diffusible element shows 1300 ° C. It can e.g. B. alloys Cobalt bases containing 0.2 to 10/0 carbon can be used according to the invention. Alloys of these elements in various combinations among themselves or with other alloy elements, such as. B. chromium, molybdenum and tungsten can be used in Depending on the composition of the metal of the parts that are joined together should be used.

Other attempts have been made with alloys containing silicon or boron undertaken. The most common concentration for boron is e.g. B. in an alloy on a cobalt basis at about 0.2 to 2 percent by weight. The most common concentration level a nickel-based alloy is 0.2 to 10% for silicon, and for a This cobalt-based alloy has a silicon content of 0.2 to 8%.

Further experiments are listed in Table III. The trials were with the alloys "PH" and with the alloys "N" of Table I in the degreased and polished condition of the corresponding sheets. As intermediate sheets those of a cobalt-boron alloy (2759) or a nickel-silicon alloy were used (2760). The connection was made in vacuo at a pressure of 0.05 to 0.07 microns manufactured. There was no pressure to ensure good contact between the adhesive surfaces applied. that in this way very useful connections are made can.

The effectiveness of carbon, boron and silicon for the invention Establishment of a diffusion connection is proven by the tests carried out been. Metals or alloys that are capable of these diffusible elements in To hold a solid solution and have sufficient ductility, as Interlayer alloy can be used in the form of thin sheets. carbon can for this purpose with cobalt, iron, manganese, titanium and with alloys of these Elements are alloyed. Other alloy partners, such as B. chromium, molybdenum and tungsten, can be present.

Silicon shows a similar solubility between room temperature and 1300 ° C and shows comparable diffusion temperatures in cobalt, chromium, copper, Iron, manganese, molybdenum, nickel, platinum, titanium, tungsten and zircon. Intermediate sheets for the method according to the invention for producing a diffusion compound can also be made using these elements.

Also boron, which has a solubility in cobalt, copper, Table IV Solubility Solubility Solubility of silicon of silicon of silicon Element in the temperature element Element in the temperature element Element in the temperature element Weight weight weight percent ° C percent ° C percent ° C Al 1.65 577 Ni 8.0 1150 V 7.5 -1840 <0.1 room- 5.0 room- 5.0 900 temperature temperature Co -7.0 1100 Pt 0.2 830 W 0.9 1800 -7.0 775 <0.2 room- 111 0.5 room- temperature temperature Fe 13.0 1250 Rh 0.5 space Zn 1.62 850 5.0 room temperature 0.06 600 temperature Mn 10.0 880 Ta 0.2 1300 Zr 0.2 1600 8.0 600 0.1 860 Ti 3.0 1330 <0.44 860 From these illustrations it can be seen that there are a remarkable number of silicon-containing alloys for use as shim, comprising the elements iron, nickel, manganese and cobalt. Nickel-based alloys with a total content of 20 to 30 percent by weight iron, manganese and cobalt, with about 8% chromium to strengthen the corrosion resistance and about 4% silicon as a highly diffusible element are excellent alloys for the production of diffusion compounds according to the invention when higher temperatures are used. These alloys, with a total content of at least 95% iron, nickel, manganese, cobalt and chromium, keep almost all of the silicon in solution at diffusion temperatures of 900 to 1000 ° C. Furthermore, they can be processed into thin strips in the form of intermediate sheets.

The compounds according to the invention were prepared in vacuo, however, a vacuum is not essential for a good bond to be formed. Of the direct contact of the parts to be connected is more important.

Can be used as intermediate sheets for the production of the diffusion connection those with a thickness of 0.62 mm are used. Thinner sheets make stronger ones Joints, and the preferred thickness range of these sheets is 0.012 to 0.12 mm.

The term intermediate sheet used here includes both strips as well as foils. Iron, palladium, tantalum and zirconium can be combined with these Metals, individually or in combination, for the purpose of making intermediate sheets be alloyed.

For the development of alloys that are used for the manufacture of a Diffusion bonding are suitable and have similar properties as the alloys of the parts to be joined, it is essential to have the solubility of the diffusible Element in the various elements of such alloys. The following Table gives the solubility of silicon in a number of important elements which can serve as intermediate sheets in elemental or in alloyed form.

Claims (7)

Claims: 1. A method for producing a ductile diffusion connection high strength between parts made of heat-resistant alloys to not molten path, d a d u r c h g e - indicates that between the intended to be connected surfaces of the parts to be connected at least one of the because of their small atomic diameter easily diffusing chemical elements from the group Boron, carbon and silicon is introduced and the parts so arranged in close contact with each other to at least 900 ° C for a period of at least 20 seconds until a strong metallic diffusion in the solid state Binding of the parts is achieved. 2. The method according to claim 1, characterized in that that boron, carbon and / or silicon in powder form, in suspended form, in Form of a precipitate from a gaseous or a liquid phase or in the form of a homogeneous alloy between or on the intended adhesive surfaces is brought 3. The method according to claim 2, characterized in that the homogeneous Alloy in addition to at least 0.1% boron, carbon and / or silicon made of iron, cobalt, Nickel, chromium and / or manganese as the base metals. 4th Method according to claim 3, characterized in that the homogeneous alloy is on Boron, carbon and / or silicon is saturated. 5. The method according to any one of the claims 2 to 4, characterized in that the homogeneous alloy in the form of a thin Sheet metal, wire mesh or powder is used. 6. The method according to claim 5, characterized in that sheets are used with a thickness below 0.65 mm. 7. The method according to any one of claims 1 to 6, characterized in that the diffusion annealing is carried out in a protective gas atmosphere. B. The method according to any one of claims 1 to 7, characterized in that the parts to be connected to one another are pressed against one another during the diffusion annealing. Considered publications: German patent application G 6481 VIa / 49h (published on October 9, 1952); ° French patent specification No. 1 196 554; "Materials in Design Engineering", 51 (1960), April, pp. 14 to 16, and 53 (1961), March, p. 9; M. Hansen, "Constitution of Binary Alloys," 1958, p. 354.