DE2032862A1 - Process for the preparation of mutual dispersions of carbides and metals or alloys and new products thus obtained - Google Patents

Description

Dr. F. Zumsteln sen. - Dr. E * Assmann Dr. R. Koenigsberger - DJpL-Phys. R. Holzbauer - Dr. F. Zumsteln Jun.

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3371/70
(Cas II)

AGENCE NATIONALE DE'VALORIZATION DE LA RECHERCHE (ANVAR),

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Puteaux / France

SSSSSSS = SS = SSSSSSSSsS - '. ■ -

Process for the preparation of mutual dispersions «SSSS S SSS SSSS S SS SS SSSS SSSSSSSS SSSSSSS SSSSSSSSS SSSSSSSSSSSSS

of carbides and metals or alloys and new, so he · * ■ ssssssBsssssssssssssssssssssssssssS'Sssassssssssssssssasssss

holding products

The present invention relates to a method of manufacture of reciprocal (reciprocal) dispersions of carbides and metals or alloys

Depending on whether the metal or the carbide is in the intended Dispersion: predominates, one speaks of a dispersion of a Carbides in; the metal or from a dispersion of a metal in the carbide.

The dispersions of the first of these two categories have with respect to the base metal or the base alloy, reinforced mechanical properties, in particular; what the durability and creep resistance, particularly at high temperature, as regards · ■

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In the dispersions of the second of the above categories the metal acts as a binder between the granules of a carbide powder to be sintered. Achieved well understood one can improve the mechanical properties of the sintered pieces.

The present invention also relates to simple or mixed dispersions of carbides in metals or alloys which have properties that make them new industrial products do.

The present invention is particularly concerned with "providing a method that is easy to perform and which ensures a constant quality of the resulting products.

The inventive method is characterized in that one

- in a first stage a mixed oxide, a hydroxide coprecipitate or a mixed complex of a first metal, such as Ti, V, Nb, Ta or Cr (or several metals, if one wants to produce a mixed carbide), which serves to make the carbide to provide the dispersion, and a second metal (or several metals, when one wants to produce an alloy) such as Pe, Co, Ni, Cu, Zn, Cd, Ag, Sn, ^Pb,:

"Bi, Ge or Tl, which serves to be the metal of the dispersion to deliver, manufactures.

- and in a second step, the compound thus obtained in a simultaneously reducing and carbonizing (carbide) atmosphere containing hydrogen and a hydrocarbon such as methane, comprising a thermal treatment of subjects whose temperature - below 1100 _C and duration are selected in such a way that the reduction of all oxides and the carburization (carbide formation) of the first metal.

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The dispersions of carbides in metals according to the invention are characterized in that they are simple or mixed Carbide particles evenly distributed in the elementary granules of the selected metal or alloy.

The particle dimensions of the dispersed ones lie in these products Phase - those not at the grain boundaries of the metallic Phase concentrated, but evenly inside the the latter are distributed - in the range from 5 to 500 nm.

In the case of the dispersion of a metal or an alloy in a carbide, the metal is located at the grain boundaries of the Carbids localized. Here, too, are the dimensions of the Particles before sintering in the range of 5 to 500mu.

If one wants to produce an metallic phase that is characterized by ■ If an alloy is formed, a mixed oxide of the metals of the second group is assumed.

In the case where the carbide of the second metal in the conditions the simultaneous formation of carbide and reduction is stable, this stage is followed by a further reduction treatment with pure hydrogen at the same temperature and a time sufficient to convert the carbide of the second To reduce metal completely.

The process according to the invention can be carried out in a fixed bed or a fluidized bed.

According to the chosen method, you can either use a device use, as shown schematically in Fig. 1, or a device of the type as shown in Fig. 2 schematically is shown.

In both cases the hydrogen and the methane or occur another hydrocarbon through lines 1 and 2, respectively a, which open into a single line 3, which the gas

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shaped mixture into the interior of a casing 4, which is heated by the heating elements 5.

In the case of Fig. 1, the casing 4 is oriented horizontally and the product 6 to be treated is in a thin one Layer distributed in a container 7 in the interior of this envelope. The treatment gas enters the surface of the Product 6 in contact.

In the case of FIG. 2, the casing is oriented vertically, with the product 6 forming a fluidized bed above the grid 8. This device allows work in the fixed bed at the same time, with the treatment gas then the layer of the product 6 penetrates.

The device of Fig. 2 allows larger amounts of the To treat product 6 in shorter reaction times than is the case with the fixed bed or the fluidized bed, in that a better contact is established between the product 6 and the treatment gas.

To give numbers, let it be said that the duration of the simultaneous reduction and carbide formation step - in the case of the fixed bed treatment with the aid of a device according to FIG. 1 · is generally 10 to 20 hours.

The proportions of hydrogen and hydrocarbon in the atmosphere used in this stage are in the range of 99.0 to 90 or 1 to 10%. In practice, one keeps within the range of theoretical proportions in order to crack the Avoid hydrocarbons.

It has been found that the carbide formation of a hydroxide or a mixed oxide, which is accompanied by a reduction of one of the metallic elements to the metallic state, according to the process according to the invention is lighter than the carbide formation of a simple oxide, which is becoming more and more crystalline

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lized and therefore less reactive. This is particularly evident in the case of the carbide formation of titanium in the presence of, for example, iron, nickel or cobalt: The carbide TiC then forms between 800 and 1000 ^° C., whereas it is impossible to obtain it in this temperature range if one has a Mixture of hydrogen / methane on titanium hydroxide [Ti (OH) ₄ ] or titanium oxide (TiO ₃ ) can act.

The dispersions of the invention made with the aid of the above Process can be used using classical powder metallurgy techniques by sintering them as they are, or it sinters after it has been mixed with the powder of a second metal when the amount of carbide in the final product. material should be reduced.

The invention is further illustrated by the following examples.

example 1

If you want to make a dispersion of a chromium carbide in iron that contains 95% iron, you start by making the mixed oxalate complex (NH ₄ ^ Fe _x Cr ^ _x (CgO _4, which is obtained by simultaneous crystallization of the complex oxalates of each of the two metals receives.

The product obtained in this way is subjected to a selective carbide formation by increasing the temperature of the product at a rate of 250 ° C / hour to 900 ° C in a gas flow which is distributed by a mixed-metering pump, the gas flow being replaced by hydrogen (21, 80 l / h) and methane (0.44 l / h) is formed, ie it contains 2% methane. After 18 hours at 900 ° C. in this atmosphere, the X-ray cristenographic analysis shows that the product obtained is biphasic and contains the orthorhombic chromium carbide C ₂ finely divided in α-iron. The product is available

in the form of a fine gray powder.

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Example 2

If you want to make a dispersion of chromium carbide in iron that contains 60% iron by weight, you start with Preparation of the mixed oxalate complex in the desired composition, as indicated in Example 1.

The product thus obtained is subjected to the carbide formation at 900 ⁰ C and at the temperature conditions and the gas flow rates, as indicated in Example 1. After 16-hour hold at 900 ⁰ C in the appropriate atmosphere rontgenkristallographische analysis shows the presence of a single hexagonal carbide Cr ₇ C _3, which is dispersed in α-iron.

Example 3

If one wishes to prepare a dispersion of titanium carbide in cobalt containing 70% by weight of cobalt, one begins with the preparation of a coprecipitate of the hydrated oxides in the following manner: at the same time, but separately, an aqueous solution of 69.1 g is added dropwise Cobalt nitrate Co (NO ₃ ) ₂ · 6H ₂ O and 23.2 g of titanyl sulfate TiOSO ₄ MH ₂ O and a 3N sodium hydroxide solution to about 1 liter of vigorously stirred water in a 2 liter Pyrex flask. The simultaneous precipitation of the two hydroxides takes place drop by drop; the very fine precipitate obtained is filtered off with. Washed boiling water until the disappearance of sulfate and sodium ions and ^{dried for 20 hours at 110 0} C in a drying cabinet.

The feinverriebene product thus obtained is subjected to a simultaneous reduction and carbide formation by raising the temperature to 800 ⁰ C at a rate of 25O ° C / one. in a gas stream which is formed by hydrogen (21.80 l / h) and methane (1.15 l / h), ie increases in a gas stream which contains 5 % methane. After holding in this atmosphere for 16 hours, X-ray crystallographic analysis shows.

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that a fine dispersion of titanium carbide TiC in cubic ß-cobalt has been obtained. The titanium carbide thus obtained at 8OO ° C is in the form of fine granules, as shown by the broad diffraction rays. .

Example 4

If you have a dispersion of titanium carbide in nickel, the 90% by weight If one wants to produce nickel, one begins with the production of the coprecipitate of the two to hydrate Oxides by following the procedure outlined in Example 3 and a salt solution of nickel nitrate and titanyl sulfate used. ·

The compound thus obtained is subjected to simultaneous reduction and carbide formation by changing its temperature in a gas stream formed by water, substance (21.80 l / h.) and methane (0.56 l / h.), which contains 2.5% methane, increases to 880 ° C. After a 16 hour hold In this atmosphere, a fine dispersion of the TiC carbide in metallic nickel is obtained.

Example 5

If one wishes to prepare a dispersion of vanadium carbide in cobalt containing 80% by weight of cobalt, one begins with the preparation of the coprecipitate of the two hydrated oxides using the procedure described in Example 3 by making a precipitate, based on a salt solution of cobalt nitrate and vanadyl sulphate caused by a three-fold diluted commercial ammonia solution. When precipitation is complete, the mixture is heated to boiling, to bring the _pH value to 7 and to destroy the vanadate, which could have formed. * '

The compound thus obtained is subjected to a simultaneous reduction and carbide formation by changing its temperature in a gas stream which is formed by hydrogen (21, 80 l / h. JLUid MsQfn Sl ^ LS l / Sfed.), Ie the 5 %

Contains methane, at 800 ⁰ C "increases after 14-hour hold at 8OO ° C in this atmosphere to obtain a fine dispersion of vanadium carbide VC in cubic .beta.-cobalt _o

Example 6

_What if you get a dispersion of vanadium carbide in iron? which contains 80% by weight of iron, one begins with the preparation of the coprecipitate of the two hydrated oxidesj using the procedure described in Example 3 and by starting the precipitate from a salt solution of iron XIX- nitrate and Va = nadyl sulfate, formed by adding a three-fold diluted commercial ammonia solution ».

The compound thus obtained is subjected to a simultaneous reduction and carbide formation ₉ by setting its temperature in a gas stream formed by hydrogen (21.80 l / h) and methane (0.44 l / h), i 'contains h _o einera gas stream 2% methane, increases to 92o C. "

After holding at 920 ° C. for 20 hours, the X-ray single crystal! © graphic analysis shows the presence of. very little a <= iron _s of cementite Fe ₃ C ₁ and cubic vanadium carbide VC. Annealing the above product under hydrogen (about 15 l / h) allows the cementite to be destroyed, and after annealing for 14 hours one obtains 920 ° C α-iron and finely dispersed Fe ₃ C (very little) and carbide VC. Another 13-hour glow at 920 ° C in a hydrogen stream then leads to the desired product, a dispersion of vanadium carbide in α-iron.

Example 7

If one wishes to produce a dispersion of niobium carbide in iron which contains 70% by weight of iron, one begins by producing an intimate mixture which has been obtained by simultaneous evaporation of the complex oxalates (HH ₄ ) ₃ [Pe (C ₂ O ₄ ) ₃ ] u

ORfQINAL INSPHCTISD

The mixture thus obtained is subjected to a simultaneous reduction and carbide formation by changing its temperature in a gas flow formed by hydrogen (21.80 l / h) and methane (0.44 l / h), ie “a gas flow , which contains 2 % methane, increases to 900 ° C. After holding at 900 ° C for 15 hours, a dispersion of carbide NbC in α-iron is obtained,

Example 8

If one wishes to produce a dispersion of a solid solution of the carbides of titanium and tantalum in cobalt, which contains 90% by weight of cobalt, one assumes an intimate mixture which was obtained by simultaneous evaporation of the oxalates CoC ₂ O ₄ , (NH ₄ J ₂ [TiO (C ₂ O ₄ ) ₂ ] and (NH ₄ ) ₃ [Ta0 (C ₂ 0 ₄ ) ₃ ] in suitable ratios, which are present in the atomic ratio of Ti / Ta = 1.

The compound thus obtained is subjected to a simultaneous reduction and carbide formation by changing its temperature in a gas stream formed by hydrogen (21.50 l / h.) And methane (0.44 l / h.), Ie in one Gas stream containing 2 % methane increases to 95O ° C. After holding at 95O ° C for 15 hours in the atmosphere given above, the X-ray crystallographic analysis shows the presence of the solid solution of the carbides TiC and TaC, which is dispersed in a mixture of hexagonal α-cobalt and cubic ß-cobalt.

Example 9

If one wants to produce a dispersion of a solid solution of the carbides of titanium and niobium in iron, which contains 80% iron, one assumes an intimate mixture, which was obtained by simultaneous evaporation of the oxalates (ΝΗ ₄ ) ₃ [Ρβ (α ₂ 0 ₄ ) ₃ ] and. (NH ₄ ) ₂ [TiO (C ₂ O ₄ ) ₂ ] and (NH ₄ ) ₃ [NbO (C ₂ O ₄ > ₃ J in suitable proportions that give a The atomic ratio of Ti / Nb ■ corresponds to 1.

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The compound thus obtained is subjected to simultaneous reduction and carbide formation by changing its temperature in a gas stream formed by hydrogen (21.80 l / h) and methane (0.22 l / h), ie a gas stream , which contains 1 % methane, increases to 1050 ^° C. »After cold for 15 hours at 1050 ° C. in the atmosphere given above, the X-ray crystallographic analysis shows the presence of a solid solution of the carbides TiC and NbC, which is dispersed in α-iron®

Example 10

If you want to produce a dispersion of chromium carbide Cr ₃ C ₃ in copper which contains 60% copper, you start with the production of the starting compound, ie an intimate mixture obtained by evaporating a solution of the citrates of copper and chromium. This solution is obtained by refluxing an excess aqueous solution of diammonium citrate for 2 hours, to which copper powder, chromic anhydride CrO ₃ and a little hydrogen peroxide are added. It is filtered in order to remove the last unaffected copper traces and the filtrate is evaporated on a sand bath.

The finely divided compound thus obtained is then subjected to W oxidation in air for 12 hours at 66o C ^0, which leads to an intimate mixture of cupric oxide CuO and cupric chromite CuCr ₂ O ^. This finely divided mixture is then subjected to a simultaneous reduction and carbide formation ^! by setting their temperature in a gas stream formed by hydrogen (21.50 l / h) and methane (0.22 l / h), ie in a gas stream containing 1% methane, to 1000 ° C increases. After 15-hour hold at 1000 ⁰ C in the above atmosphere, shows the X-ray, kristenographische analysis that 'a dispersion of chromium carbide ^Cr 3 ^C received 2 ^ ⁿ copper.

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Example il

If you want to produce a perronickel alloy containing 48% iron and 52% nickel with 3% vanadium carbide in finely dispersed form, one begins with the production of the starting product, ie a coprecipitate of the three hydrated oxides using the procedure as described in Example 3, starting from a salt solution of ferric nitrate. Nickel chloride and vanadyl sulfate, a precipitate forms · ammonia by addition of 25%, by operating at a p _H value of ~ 7.5.

The compound so obtained undergoes a simultaneous reduction and subjected to carbide formation by changing their temperature in a gas stream which is formed by hydrogen - (21.80 l / h) and methane (0.44 l / h), i.e. one. Gas stream containing 2% methane, 'increases to 95O ° C. To Hold at this temperature for 15 hours in the above specified Atmosphere shows the X-ray crystallographic analysis, that a dispersion of vanadium carbide VC in perronickel is obtained with a cubic, flat surface. Structure _ similar to the -g * iron with a lattice constant a = 3.585 Α

Example 12

If you have a dispersion of 3% by weight of titanium carbide in a If you want to produce a nickel-cobalt alloy of the composition 90% by weight ^ .Ni and 10% by weight Co, you start with the Prepare the coprecipitate of the three hydrated oxides using the procedure described in Example 3 was made by starting from a salt solution of the chlorides of nickel, cobalt and titanyl sulphate in suitable. Conditions, a precipitate is formed by adding 3N sodium hydroxide solution. "■■ ..-:

The compound so obtained undergoes a simultaneous reduction and subjected to carbide formation by changing their temperature in a gas stream that is formed by hydrogen

■ 00988541525.

(21.80 l / h.) And methane (0.22 l / h.), I.e., a gas stream, which contains 1% methane, increases to 1O2O ° C »After 16 hours Hold at 1O2O ° C in the atmosphere given above the X-ray crystallographic analysis that one is a ß-nickel-cobalt alloy with a face-centered cubic structure, which is very similar to that of nickel, has received the one Dispersion of titanium carbide TiC contains »

Example 13

If you have a refractory composition based on Titanium carbide, which contains 6% by weight of cobalt, which serves as the binding phase during sintering, is to be produced, so one begins with the preparation of a coprecipitate of the two hydrated oxides by following the procedure outlined in Example 3, applies, forming a precipitate starting from "an aqueous solution of titanyl sulfate and cobalt chloride in suitable proportions by adding 25% ammonia. During the whole process the p "value should not exceed 8.

The compound thus obtained is subjected to simultaneous reduction and carbide formation by changing its temperature in a gas stream formed by hydrogen (21.80 l / h) and methane (0.22 l / h),, d, » H. a gas stream containing 1% methane, increases to 1030 ° C. After holding at 1030 ^° C. for 20 hours in the atmosphere specified above and cooling, a gray-black powder is obtained. The X-ray crystallographic analysis confirms the presence of face-centered cubic titanium carbide TiC and a face-centered cubic binding phase of ß-cobalt.

It goes without saying that the present invention does not relate to the embodiments mentioned in the description is limited, but also includes all variants.

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Claims (5)

Claims S SS SS SS -SS SS ± 5 SSl -SS SS SS SS SSSS SS S SS-SS SS S S 2 SSSS SSSS SS-JS SS ■. ■ ■ ■ ι ■ 1.) Process for producing a mutual (reciprocal) Dispersion of carbides and metals or alloys, characterized in that one - in a first stage a mixed oxide, a hydroxide coprecipitate or a mixed complex of a first metal such as Ti _? V, Nb, Ta or Cr (or more metals if you want to get a mixed carbide), which serves to form the carbide of the dispersion, and a second metal, such as Fe, Co, Ni, Cu, Zn, Cd, Ag, Sn, Pb, Bi, Ge or Tl (or several metals, if you want to obtain an alloy) that forms the metal of the dispersion, - in a second stage the compound thus obtained in a simultaneously reducing and carbidbiIdenden atmosphere containing hydrogen and a hydrocarbon such as methane, comprising subjecting to a thermal treatment, whose temperature • -unterhalb 1100 ⁰ C -> and duration are selected in such a way that the reduction of all oxides and the formation of carbides of the first metal are ensured, the increase in temperature preferably taking place at a rate in the range from 100 to 40 ° C / h; d _s . 2.) The method according to claim 1, characterized in that the step of simultaneous reduction and carbide formation in is carried out on a fixed bed 3.) The method according to claim 1, characterized in that the The simultaneous reduction and carbide formation stage is carried out in a fluidized bed. 4.) Method according to claim 2, characterized in that «the duration of the simultaneous reduction * and carbide formation stage is in the range of 10 to 20 hours« 00988571525 5.) Process according to claim 1 to 3, characterized in that the ratio of hydrogen to hydrocarbon in the atmosphere used during the simultaneous reduction · * · and carbide formation stage is in the range from 99 to or 1 to 10 % · 6.) Process according to claim 1, characterized in that in the case that the carbide of the second metal is stable under the conditions of simultaneous carbide formation and reduction, this stage is followed by a further reduction treatment with pure hydrogen at the same temperature during a period of time sufficient to completely reduce the ψ carbide of the second metal ζμ, 7 ·) Dispersion of simple or mixed carbides in a base metal or a metallic base alloy, thereby characterized that di.c particles of the simple or mixed Carbides evenly in the elementary granules of the selected base metal or the selected base alloy are distributed. 009885 / 152S