DE2148390C3 - Cobalt alloy and process for its processing - Google Patents

Description

where in the presence of titanium and aluminum

and / or niobium the iron content max. 10%
which, if there is no titanium, also

is free of aluminum and niobium, or in the case of a titanium, the invention relates to a cobalt alloy. Included

content of ibis 5% also aluminum and / or niobium 20, the invention is particularly concerned with a

contains with the proviso that the mathematical cobalt alloy, which in combination mi:

matic expression of excellent corrosion resistance, high strength

N η M Kij.nir _n jm Fp ^and ductility, one in a cubic

^ T (Ir , Λ * Z, 'face-centered matrix dispersed, platelet-

-t- 4.00 er -r 3.00 Mo, _{25-shaped Cj has} hexagonal close-packed phase and

in which the chemical symbols are essentially free of embrittling phases,

mean effective atomic ratio in which the as well as with a method for processing such

the element in question is contained in the alloy, alloys.

Defined number of electron gaps N _v in the case of alloy- In the following, all percentages apply in counter with an iron content of 16 to 25% high weight percent.

»Is at least equal to 2.55 and alloys with From US Pat. No. 33 56 542 there is already a cobalt one Iron content of more than 6 to 16% a nickel-chromium-molybdenum alloy known to be made up Does not exceed value of (2.82 - 0.017 Wpe), 5 to 45% nickel, 7 to 16% molybdenum, 13 to 25% Whereby in the above expression "W ^ e" the chromium, up to 0.05% carbon, up to 2% aluminum-iron content of the alloy in percent by weight 35 minium, up to 2% titanium, up to 2% zirconium, up to means. 6% iron, the remainder at least 25% cobalt, with

2. cobalt alloy according to claim 1, characterized in that the sum of the contents of aluminum indicates that it is titanium, aluminum and minium, titanium and zirconium not greater than 4%. is niobium-free. Furthermore, this known alloy is the sum

3. cobalt alloy according to claim 1, characterized in 4 ° of the contents of cobalt and nickel between 62 and characterized as being titanium and at least 80% and is the ratio of the sum of the contents contains one of the elements aluminum and niobium. of cobalt and nickel for the chromium content at 2.6.

4. cobalt alloy according to one of claims 1 This known alloy is corrosion resistant and to 3, characterized in that it can at most under certain temperature conditions through Contains 23% iron. 45 deformation or machining are hardened so that

5. cobalt alloy according to claim 3, which then has very high tensile strengths and yield strengths characterized in that it contains at most 10% iron. Alloys of the type mentioned can be used in contains. Depending on the temperature in one or two

6. Process for processing a cobalt crystal phase or modifications exist and Alloy according to one of the claims Ibis 5, characterized by 5 ° characterized by one of their combinations, that they are at a temperature-dependent transformation temperature range below the range in which the hexagonal from, in which transformations of the one crystal tightly packed Phase in the face-centered cubic modification in the other take place at above the Phase converts by at least 5% to the lower limit of the transition temperature range Cross-sectional area related, is cold-formed. 55 lying temperatures are the alloys in the

7. The method according to claim 6, characterized in that the cubic face-centered (CFC) modification is stable, draws that the cold deformation at room- At temperatures below the lower limit temperature he follows. temperature of the transition temperature range,

8. The method according to claim 6 or 7, characterized in contrast, the hexagonal close-packed (HDG) characterized in that the ^{degree of deformation high-6} ° modification resistant. By cold working of at least 70%. metastable, cubic, face-centered material

9. The method according to any one of claims 6 to 8, one below the lower limit of the transition thereby characterized in that the alloy is a temperature before a temperature range the cold deformation is annealed in a homogenizing manner. Part of the material in the hexagonal close-packed

10. The method according to claim 9, characterized in ^{6 converted} 5 modification, which then indicates in the form of that the homogenization is present in the platelet, which takes place in a matrix of cubic temperature range from 1121 to 1177 ^C C. face-centered material are distributed. On this

11. The method according to any one of claims 6 phase transformation under the effect of a cold

Deformation are based on the excellent tensile strength - cheaper alloy elements can reduce it

and yield strengths of the known alloy. be seen in that by using

However, this known alloy is the occurrence of cheaper alloy elements

disadvantageous as they feared high contents of relatively expensive brittle phases in the material. at

Alloy elements such as nickel, molybdenum and such brittle phases are topological

Cobalt, required and also especially with increased densely packed phases, such as the sigma-, my- or chi-

Temperatures above unsatisfactory intrinsic ductility phase.

stocks. Thus, the known alloy possesses the alloys according to the invention

at most 6% iron and already loses its ductility in platelet-shaped, hexagonal close-packed phase, the

at relatively lower temperatures of 10 in a matrix of a face-centered cubic

for example 149 to 204 "C, provided the known crystal phase is embedded.

Alloys with the highest tensile strength considered The iron content of cobalt alloys according to the invention

will. is preferably a maximum of 23%.

The invention is therefore based on the object, As already mentioned above, the

to create a cobalt alloy, which savings 15 cobalt alloys according to the invention are titanium-free,

designed on expensive alloy elements and although they are then neither aluminum nor

Nevertheless, they may contain essentially about the same good niobium. On the other hand, the

Has performance properties like the known cobalt alloys according to the invention but 1 to 5%

higher contents of high-quality components contain titanium, but then at least one of the

holding alloy. This task includes 20 elements aluminum and niobium in the above

the requirement to create a cobalt alloy, specified maximum levels must be present.

which its ductility even at elevated temperatures. So titanium in the alloy is in the specified range

maintains. Salary limits of 1 to 5%, so AI must also

According to the invention, this object is achieved by minium and / or niobium being present, whereas

a cobalt alloy, consisting of 0 to 0.05% 25 in the case of titanium-free alloys also aluminum and niobium

Carbon, 18 to 40% nickel, 6 to 12% molybdenum must be missing.

15 to 25% chromium, more than 6 to 25% iron, 0 to Furthermore, it should be underlined that with titanium-containing 0.1% boron, 0 or 1 to 5% titanium, 0 to 1% aluminum, alloys, which accordingly also contain AIu-0 to 2% niobium, the remainder cobalt, with the presence of minium and / or niobium, the iron content of titanium and aluminum and / or niobium, the iron content being a maximum of 10%. This titanium-containing maximum is 10%, which, if no titanium is present, cobalt alloys are a special design, also free of aluminum and niobium, or in a form of the invention that is also aluminum and or due to a high tensile titanium content of 1 to 5% strengths and contains niobium even at high temperatures with the proviso that they are characterized by permanent ductility.
Mathematical expression 35 alloys which are only their composition N _v = 0.61 Ni + 1.71 Co + 2.66 Fe + 4.66 Cr ^{according to} limits within the above-mentioned content of 4-5 66 M, but not the restrictive limits Conditions with regard to the electron gap number N ₁ , in which the chemical symbols in each case suffice, do not belong to the effective atomic ratio according to the invention, in which this means 40 alloys, since they can be rich in brittle phases. relevant element is contained in the alloy, alloys according to the invention are characterized by a defined electron gap number N _v in alloys that, depending on the alloy composition, with an iron content of 16 to 25%, the maximum value for the electron gap adjustment is 2.55 and for alloys with an iron - are not exceeded, as an excess of more than 6 to 16 percent by weight does not exceed a specified maximum value for the occurrence of brittleness of (2.82 - 0.017 W _Fe ), whereby phases lead.

in the above expression "(Vv _e " the iron content of the alloys with an iron content of 16 to

Alloy in percent by weight means. 25%, but preferably up to a maximum of 23%,

With the aid of the cobalt according to the invention, the number of electron gaps may reach a maximum value of

alloy compared to the known cobalt alloy do not exceed 5 ° 2.55. For alloys with a

Achievable technical progress is primarily iron content between 6 and 16% are higher Λ 'values

to see that the alloy according to the invention is permissible, the maximum permissible value being at

Because of their high iron content, it is cheap on the alloys with 6% iron.

Can be brought to the market without this being able to iron, amounts to 2.72. For alloys with a rich alloy in its properties of the well-known 55 iron content of more than 6 to 16% is the permissible

Alloy would be inferior. The maximum value according to the invention of the electron gap number N _v by the

Alloys in which titanium and aluminum have a mathematical relationship

and / or niobium is present, are distinguished from the ^ ^ 2 87 - 0 017 HV - known alloy in that they are also at

maintain their ductility at elevated temperatures. 60 defines in which HVo the iron content of the Le

Because of its excellent mechanical properties, it is represented in percent by weight. The influence of voi

Shafts even at "higher temperatures are the carbon and / or boron with respect to the electrons

Cobalt alloys according to the invention, in particular gaps, are negligible in these alloys

for use in jet engines by aviation passengers.

testify suitable. 65 The electron gap number N ₁ - is a measure of di

The reason for the fact that the specialist world has not up to now an average number of Elcktronenfehlstellc

had gone over to the proportion of extremely expensive or gaps in the 3d sub-shells from Chrorr

1 Ruierunesclementc through increased use of priced cobalt, iron and nickel! as well as the 4d unlcr shell

5 ^v 6

of molybdenum. The formation of brittle phases is discussed in.) Furthermore, it is assumed that the particular alloys can be associated with these electron formation of these compounds to a precipitation gap, since this hardening of the alloys in question leads to the electrons being transferred to those of transition ^ smetallen einge- the conversion of CFC phase in HDG-to-phase gangenen chemical bonds are involved. Supplemented by 5 traceable hardening effect and thus the definition and meaning of the »effective atomic possible, a higher tensile strength with less strong percentages«, which are used to calculate the Λ ',. Used to achieve cold working or deformation, as this will be, to understand, one has to go further than what was previously possible.

information on the microstructure of the alloys for the "effective atomic ratios" of the elements

»Nd with regard to the relationship between the structure io in these alloys, which are used to calculate the

and the properties of the alloy. tronenlützenzummer / V, -be used is the above

As already mentioned, it is assumed that the postulated conversion of a portion into account existing transformation of a metastable phase in CFC Metallatomc platform, in particular nickel atoms, in conjunc- phase HDG Chen from stable the reason for the high fertilize the formula Ni X ₁₁ .
Tensile strength of both the known and the 15 Thus, in the case of alloys that do not contain titanium (and consequently cobalt alloys, since also no aluminum and / or niobium), a theory developed in this regard is the formation of the "effective atomic ratio" of each of these Platelets from HDG phase in the CFC matrix existing elements equal to the actual atom the relative movement or translation along the sliding ratio in which the element in question inhibits or prevents existing planes that are responsible for the failure 20, since none are present in these alloys Forming compounds of metals or breaking or tearing of metals of the formula Ni ₃ X.

responsible for. However, the Duk alloys, the "X" or "hardening elements"

tility of these alloys with the phenomenon of (titanium, aluminum and / or niobium)

Bring the phase transformation into relationship, and one first has the total atomic percentage for each of the in

indeed the surprising ductility of these elements in a given alloy

gations the occurrence of a phase change is calculated from the respective proportion in percent by weight.

deformation, such as in a tensile test, where carbon is present in the alloy

attributed to. In any case, the proportions are insofar and / or boron is disregarded. The respective

far unequivocally clear when it is established that enictility gives the total atomic percentage the number of atoms

of these alloys, the lower the strength of the element in question, the lower it is in the alloy

they are cold-worked or cold-hardened and the higher 100 atoms are present. The total atomic

their tensile strength is. Percentages of hardening elements are totaled

Thus, the alloys lose ductility if and multiply the sum by 4, which results in the

cold machined to increase its strength it contains the approximate number of atoms that is different from 100 atoms

will. Furthermore, the remaining ductility in the alloy takes part in the formation of Ni ₃ X

continues to decrease with increasing temperature. are. However, this value still needs to be corrected.

The loss of high temperature ductility suffered by Le-RW Guard and employees in an in gation, for example, when they were employed as a security company. Aime, 215. 807 (1959), published articles supply medium in a flying jet engine used "The Alloying Behavior of Ni ₃ Al (gamma prime is, the ability of such a reduced fastening 4 ° phase)" showed that cobalt. Iron, chromium and molybdenum agents to adapt to a locally concentrated problem in such a Ni ₃ X compound in amounts of stress or point stress and these occur up to 23, 15, 16 or 1%. To compensate for the peak atomic load and thus the percentage, or the number of atoms per 100, can lead to failure or breakage, while determining an atom for each of these metals, the more ductile material would deform to become 45 as well the Ni ₃ X phase is bound and thus to adapt to such a stress and not compensate for the formation of a voltage that _{does not consist of Ni 3 X.} Alloy matrix is available, approximately

One way of obtaining ductility is to determine the maximum prior art alloy for each metal is to use the percentage solubility product in Ni ₃ X, the atomic extent of the cold working or deformation 5 ° ratio in which it will decrease in the alloy in question. Less heavily cold worked alloys are included and the total number of atoms, which however also have a lower tensile strength. be present _{as Ni 3} X per 100 alloy atoms

The alloys according to the invention that can contain titanium are formed or determined.

Combination with aluminum and / or niobium contain, the number of Ni, Co, Fe, Cr · and Mo atoms, overcome the above-described, in alloys, those present in the respective alloy according to the prior art The given problem, are then corrected by subtracting the numerical value of the cobalt according to the invention, which represents the subset of the metal which has already been met with less severe cold working and which is in the Ni ₃ X phase or deformation ( The difference formed in this way gives, in addition to the ductility at elevated temperatures, a higher proportion of the nominal composite tensile strength achieved than with alloys. sctzung or the total alloy-related atoms which do not contain the elements mentioned. Percentage again, which in the TU for the learning

It is assumed that these elements are available for Vcr matrix formation (more actual

form bonds of the formula »Νί, Χ«, in which X is titanium. Atomic percentage). As the sum of the actual

Means aluminum and / or niobium. (It will be auge- 65 atomic percentage less than 100 is'., Then it will be for

it is assumed that in these compounds the elements mentioned are each related to this sum

Elements calculated to some extent by other elements "effective alom percentage". The effective one

Substituted, which is detailed below in atomic ratio. which divides the by 100

represents effective atomic percent salt, is finally used to determine the number of vacancies N ₁ . of the alloy in question. This calculation is explained in detail below using an example.

To prepare the erfindungsgcmüßen Kobaltlegicrungcn the components are first melted, and that suitably by vacuum induction melting at a temperature of about 1482 ^C C. Because of the relatively high iron content of the erfindungsgemäßcn alloys can be used of chromium and molybdenum to produce the melt ferroalloys, whereby a considerable cost advantage is achieved. According to a typical procedure according to the invention, most of the iron is added in the form of ferro-alloys.

The molten alloys can be cast into bars or with one directed towards a surface A gas jet is applied, whereby the melt is dispersed in the form of small droplets, which solidify to a metal powder, which is used for the powder metallurgical processes described below Procedure can be used.

If desired, ingots cast from the melt prepared as above can be prepared according to the Cooling in a consumable vacuum furnace is further treated to form the ingot structure to improve and reduce their gas content.

It is well known to the person skilled in the art that under practical working conditions when solidifying alloys, especially in the form of bars. Nucleation occurs. This nucleation leads to the formation of the dendrites in the microstructure and, in the case of the refined alloys, causes an increase in the number in the material between the dendrites. This is due to the fact that the material which first solidifies when the alloying melt cools down has a relatively high content of cobalt and nickel, ie elements that have only a relatively low tendency to form embrittling phases, such as the sigma phase. The material that solidifies last and contains a relatively large amount of chromium and molybdenum, on the other hand, has a higher number of electron gaps and tends to form embrittling phases. As a result, certain alloys according to the invention, namely in particular those with a composition which have an electron gap number Ν _υ that goes towards or near the maximum permissible value, can contain the sigma phase in the cast state. The cobalt alloys according to the invention are therefore preferably homogenized by annealing them at temperatures below their melting point, expediently at temperatures from about 1121 to about 1177 ° C., for 18 to 36 hours in order to achieve homogenization by diffusion of the elements and sigma phase or to completely eliminate other embrittling phases that may be present in the alloy in the as-cast state.

After homogenization, the alloy ingots are usually used in preparation for rolling pressed and then rolled out to suitable shapes and sizes for further treatment or processing. (You can choose to have the bars after homogenizing and before any processing or deformation Crush into powder.) The pressing is, if necessary with large bars, at a temperature of 1013 to 1149 "C and can become a Reduce the area by about 4: 1. The rolling is carried out at the same temperature and can lead to a further reduction in cross-section or area of around 40: 1.

The (hot) rolled material can then optionally be ^{annealed at a temperature of about 1052 to 1066 °} C. for about 1 hour in order to achieve a uniform structure for the subsequent cold working or shaping.

The cold deformation is carried out at a temperature below the lower limit of the temperature range in which the transition from the cubic, flat / centered high-temperature phase to the hexagonal, close-packed phase, which is stable at low temperatures, takes place. As a rule, cold working is most expediently carried out at ambient temperatures which, in a conventional rolling mill, can fluctuate ^{between approximately −18 and + 43 ° C., for example.} These ambient temperatures are far below the lower temperature limit of the transition temperature range of all cobalt alloys according to the invention.

When cold working is done at a temperature above ambient is to be, the limit temperatures of the transition temperature zone for each determine the individual alloy composition easily. For example, this is initially a Sample of the alloy in question is cold-worked at ambient temperature so that a cross-sectional or area reduction of about 50% achieved. The cold deformation under these conditions results to a phase transformation, which in turn results in the formation of embedded in a CFC phase matrix HDG phase plate leads. These phase differences are in electron micrographs (linear magnification 2000 to 3000) of the alloy can be clearly seen. Different parts of the cold formed Sample, e.g. B. slices from a rod or a rod, are then each about 8 hours at temperatures differing by about 10 or 38 ° C in one range between 427 and 816 ° C, depending on the Composition of the alloy, heated. Then electron micrographs are taken each the differently heat-treated specimens examined. The temperature at which the HDG platelet phase begins to disappear from the original two-phase structure is the lower one Temperature limit of the transition zone. The temperature at which the HDG platelet phase is complete disappears so that only the CFC matrix phase remains, the upper limit temperature is dei Conversion zone for an alloy with the examined composition. In the case of the below be In the alloy according to Example 1, the transformation temperature range is, for example, unge between 593 and 732 ° C.

Cold working cast alloys is below the lower limit of conversion temperature range can be achieved using any conventional method, such as rolling Forging or drawing. However, it is preferable to use cold drawing or rolling because a more uniform product is obtained. When drawing into round bars or profiles, di Annealed materials are first ground centreless

9 ίο

to remove the hot-rolled skin and hot-work uniform alloys. Often everyone is To achieve borrowed ingot size, so that the further tensile strength area reduction caused by the hot forming Easier con-loss acceptable due to cold forming. For example, you can go out ! can be rolled or regulated. After the centerless, previously cold-formed material or semi-finished product, grinding the material is properly lubricated. 5 objects by partial hot forming (e.g. with ζ Produce B with a coating of lime and / or molybdenum - e.g. IO38X). Although in wanmerformten disulfide, and then cold drawn. Part of a certain loss of tensile strength may occur Manufactured in the manner described above this can be tolerated if the thermoformed part Alloy powders can be exposed to less stress than those treated in various ways will. For example, the powders can be used in parts that have not been thermoformed. A such an object can thus on the one hand be certain to form bodies of the desired shape hot or cold pressed and then have the known desirable strength properties sintering powder metallurgical techniques. Which at the same time and on the other hand offer the advantage obtained moldings can then, for. B. by simple, appropriate and relatively inexpensive Embossing, cold-forming. > 5 to be producible.

Another technique is the alloying. The examples illustrate the invention and its

powder on a substrate, e.g. B. a different metal, has numerous advantages.
to which it sticks, hot or flame sprayed (e.g. by

so-called »plasma spraying«) and then in situ in B e i s ρ i e 1 1

suitably, e.g. B. by forging, rolling or 20

Hammering, cold worked. From a batch weighing about 22.6S kg from cold forming or machining, 4.49 kg of electrolyte chrome is obtained. 5.23 kg of nickel, 6.94 kg that a cross-section or surface min- cobalt, 2.31 kg molybdenum, 0.018 kg nickel-boron derung'von at least about 5% is achieved. The and 3.95 kg electrical iron became an alloy with the most favorable tensile strength values developed in 25 J80 with an electron alloy that produced a cold setting leading to a cross-sectional area gap number X of 2.52 and the following reduction of at least about 30% :

have been subjected to deformation or processing. ·. ,,, "". ",.".

As already explained above, the _ Ge ^ ht%

Alloys have a higher strength, the stronger the 30 J- ^ ¹¹

they are cold worked. With increasing strength ™ ^

on the other hand, the alloys will always be ^ r 1 _.4

less ductile. Accordingly, the alloys - ^ o - "<" · *

gen, for example if they are used to produce «1 /.^

Wire used in practice only up to 35 pounds' - ^ ₁

an area reduction of at most 70% cold- ~ -

deformed, although until a reduction in cross-sectional area is achieved Cold worked up to 95%. The above listed ingredients have been could become. When an even greater ductility in a vacuum furnace at a pressure of 0.25 ton is desirable, as for example with alloys that are 40 and a temperature of about 14S2 C in one to be processed into fasteners, so MgO crucibles melted. The alloy was In the Reeel, a cross-sectional area is enough refined until it degenerates every 5 minutes between 50 and 60% off. In the case of the weight loss rate measured according to the invention, essentially according to cobalt alloys that borrowed titanium in combination was constant.

containing aluminum and / or niobium can 45 The melt was then turned into a cylindrical

Desirably high tensile strengths (182.8 to steel mold cast with a copper team and zui

196.9 kp'mm ⁵ ) with a cross-sectional area vennine solidification. After cooling down there became:

deruno of around 35 to 45% can be achieved. This vacuum was broken, the furnace opened and the mold

Alloys have a particularly good ductility from the cast block, which has a diameter:

and maintain their ductility even at an elevated 50 of about 8.89 cm and a length of about 38.10 cn

Temperatures. ^be sat-

To increase the strength, the cold- As the shape of the ingot allowed this, e

Deformed alloys are then milled for about 4 hours directly at a temperature of li21 "C

a temperature of about 427 to 732 ⁼ C - its diameter was reduced to 1.91 cm

divorce hardened. In the case of titanium-free alloys 55, which corresponds to a cross-section reduction of about 22 ::

the preferred curing temperature is approximately corresponding.

482 ° C. If titanium is present, higher are the hot rolled material was then 1 hour

Curing temperatures of about 649 ^r C pre-annealed at 1052 "C and then through sharpening

draw. After hardening, the alloys are loosely grinded to a diameter of ctw;

cooled in air. It should be noted that the 6c brought 1.80 cm.

Cobalt alloys according to the invention also at over The ground rod was then under Venvendun

the upper temperature range of the conversion of a lubricant made of lime and molybdenum disulfide

temperature range to "objects desired drawn to a diameter of 1.27 cm. The them

Shape can be thermoformed. The resulting 50 ° / ₀ igc cross-sectional surface area treated in this way

Alloys, however, do not have such a high degree of strength, which would take about three stitches with a flat

values, such as alloys, achieved in the above reduction of 20% each. The Kaltverfoi

were cold-formed in the manner described. Measurement was carried out at ambient temperature, i.e. H. sth

It is also possible to carry out previously cold-formed 21 ^° C. according to the invention.

The kaltvcrformlc alloy was then cured for 4 hours at 510 ⁰ C and then cooled in air. Then specimens were removed and ground for testing. The alloy exhibited the following properties:

tensile strenght
(kp / mm ')

0.2 limit c

(kp / mm ² )

strain

Co)

195.9
192.9

190.9

188.7

6.5
6.5

Cross section reduction

C)

31.3
30.4

Was the same alloy only up to a reduction in area cold-formed by 38% at 21 C, the following properties were found:

Tensile strength 0.2 limit
{kp / mm ² ) (kp / mm =)

strain

Cross-line reduction

152.7
152.6

140.9
141.2

7.5
7.5

18.4
32.4

Although the cobalt alloys of the invention are significant contain more iron than those known from the aforementioned LiSA. Patent No. 33 56 542 Alloys, they surprisingly have a higher corrosion resistance than the State-of-the-art alloys.

In a test to determine the corrosion resistance, a controlled voltage was applied by means of a potentiostat to a cell with a saturated calomel cathode and the alloy to be tested as the anode. As the electrolyte was a 3.5 ° / _o igc used sodium chloride solution. The current flowing through the cell was measured. whereby, according to Coulomb's law, the corrosion that occurs is all the less. the smaller the observed current is.

The annealed and up to a transverse reduction of 50 " _n cold-formed alloy .180 showed the following corrosion characteristics in this test:

voltage
(V)

electricity
(Milliamps)

0.2
0.4
0.6
0.8

0.015
0.05
0.095

(Stress-free potential seeen über eesättietem Calomel = 0.3 V.)

In contrast, a typical, iron-free Prior art alloy (the composition of which is given below) is as follows Test results:

voltage
(V)

electricity
(Milliamps)

0.2 0.04 0.4 0.02 0.6 0.13 OR 1.2

(Stress-free potential versus saturated calomel = - = 0.174 V.)

This prior art alloy, which was annealed before the test and _{cold worked to an area reduction of 47.5 "0} , had the following composition:

Weight percent

C 0.02

Mon 10

Cr 20

Co 35

Ni 35

In another test to determine the resistance of the alloys to corrosion cracking (i.e. corrosion under anaerobic conditions in which an oxygen concentration gradient is generated which leads to the formation of a concentration index), rods of the alloy J 80 and the alloy according to the prior art in the longitudinal direction _i immersed _solution: 72 hours in a 10 ⁿ / _o aqueous FeCl wrapped with a stretched rubber band, and at room temperature. Under these conditions, neither alloy showed corrosion cracking. The extent of general surface corrosion was measured by determining the weight loss per unit area.

Weight loss tmg / 6.45 cm ¹ ) 35 JSO 1.38 "" cold formed) 1.1 J 80 (50 "kait-deformed) 1.2 State of the art 1.4 (30 "" cold worked) State of the art 3.2 40 (30 °, cold-formed)

(All four alloys were aged for 4 hours at 538'C after cold working.)

These tests show that the alloy according to the invention, despite its high iron content, both surprisingly with regard to the crack corrosion resistance as well as the general corrosion resistance Has properties which with those of an iron-free nickel-cobalt alloy according to the prior art are comparable to the technology.

Examples 2 to 7

Analogously to Example 1, a number of further alloys with the compositions shown in Table I below were produced. While the percentage composition of all these alloys is in the range _{according to the invention disclosed further above, the electron gap number jV r} in certain of these alloys lies outside the limit values permissible according to the teaching of the invention. These alloys are not alloys according to the invention and are listed for comparison purposes only. (In addition to the elements listed below, all alloys also contain 0 01 ° boron and 0.015% carbon.) '°

Table I.

Mon

Cr

Co

Fc

Ni

J 83
J 84
J 88
J81
J82

10.0

7.0

8.5

10.4

10.8

9.0

20.0
20.0
20.2
19.8
20.3
20.5

31.5
40.0
30.3
31.6
32.8
31.5

9.5
12.0
19.3
17.0
16.7
19.0

29.0
21.0

19.4
20.0

2.40
2.43
2.54
2.56
2.61
2.58

The alloys J 81, J 82 and J 85 all contain In start in the sigma phase and are too brittle. lim to be processed. The average properties of the remaining alloys after processing as in Example 1 are shown in Table 11!

Table II

alloy tensile strength 0.2-Grcnzc elongation

speed lacing

(kp / mm ^! ) (kp.'mm ") ("") t °")

J 83 203.4 193.13 2.7 8.6 184 202.27 180.62 5.2 21.9 388 183.78 170.01 8.2 40.4

Example 8

It is useful in the large-scale production of alloys. Use ferrous alloys. Accordingly, a (tSO-kc batch by vacuum melting 122.02 kg of low carbon dioxide Ferrochrome, 67.13 kg pure molybdenum, 157.85 kg nickel, 206.84 kg cobalt. 39.9 kg of chrome. »Produced 6.2 kg of iron, 0.45 kg of nickel-boron and 0.045 kg of additional carbon.

The alloy produced in this way had the following bath analysis:

C. ... . . 0011 Si o.m Mn O 03 S. 0 003 P. O 008 Cr ... 18 96 Mon 9S6 Co ... 30 33 Fc 17 60 B. 0 01 Ni rest

Example 9

The beneficial effect of hot aging after cold forming is based on a comparison of the properties just listed below with those of the cold formed. and hot aged alloy according to Example 1 with the properties listed below of the same alloy immediately after cold working. H. h. to be seen before hot aging.

Bullet strength

0.2 limit (kp / mm ⁵ )

strain

Constriction

50% drawn (mean from two samples)

153.3 144.1 8.8 41.0

38% drawn (mean from two samples)
' 137.1 105.5 13.5 45.5

Example 10
As in Example 1 was by melting. Pour

and rolling the following Legiciun

made with the ChiHYe .1153:

Weight prvw

C 0.015

Mo 7.0

Cr 19.0

Co 35.7

Fc 9.0

Ni 25.5

B 0.015

Ti 3.0

Al 0.2

Nb 0.6

The effective atomic percentages and the FIeV troncnlückcnzahl .Y, were calculated for this alloy as follows:

First of all, de Share in atomic biology neglecting vo Boron and carbon calculated:

Mon
Cr.
Co.
Ic.
Ni.
Ti.
Al.
Nb

Alom percent
(Number of
Atoms to 100)

... 4.25

... 21.29

.. 35.30

... 9.39

, .. 25.31

... 3.65

... 0.43

... 0.38

100.00

The number of U. "irterelcmcnt - (" X ") - atoms p; 100 alloy atoms or the sum of their atoms; v percentage / c is (3.65 + 0.43 -4-0.38) = 4.46. D; uncorrected total number of an The nickel and X alloys involved in the formation of Ni ₃ X amounted to (4 · 4.46) = 17.84, of which 13.38 are nickel atoms. «that (on 100 alloying atoms) (25.31 - 13.38) --- 11.9 nickel atoms are available for matrix formation.

The number or the atomic percentage of molybdenum atoms that go into the Ni _{; l} \ phase is the product! - from the solubility of molybdenum in Ni ₃ X. de; The atomic ratio of molybdenum in the alloy and the number of Ni ₃ X atoms and amounts to scm (0.01 · 0.0425 · 17.S4) = 0.01. so that (4.25 - 0.0

5Q = 4.24 atoms of molybdenum per 100 alloy tones remain for the matrix formation. For chromium into the Ni ₃ X Phasc ergii continuously to analog manner atomic percent of (00:16 · 0.2129 · 17.84) = 0.6 and thus available for the matrix formation bz 'actual atomic percent of

(21.29-0.61) = 20.68.

The corresponding values for cobalt can be calculated sii

to (0.23 · 0.3530 · 17.84) = 1.44 or (35.30 - 1.4 = 33.86. For iron, the corresponding values are calculated as (0.15 · 0.0939 - 17 84) = 0.25. bz (9.39-0.25) = 9.14.

This results for the individual alloy

elements following atomic percentages, corrected or atomic percentages available for matrix formation;

on the sum of the corrected atomic percentage

related effective atomic percentages and effective atomic ratios:

Uncorrected Corrected More effective Effective atom or available atom atom percentage atomic percentage ratio (Number / 100) rate

Mon 4.25 4.24 5.31 0.0531 Cr 21.29 20.68 25.90 0.259 Co 35.30 33.86 42.39 0.4239 Fe 9.39 9.14 11.45 0.1145 Ni 25.31 11.93 14.95 0.1495 Ti 3.65 - Al 0.43 - Nb 0.38 - 100.00 79.85 100.00 1.0000

The influence of cold deformation on the tensile strength and ductility can be seen III with Table IV below a comparison of the table in which the corresponding Legierungseigenschäften are aufeeführt of samples of the same alloy, but cold-formed to reach a 46 ° / _o by weight necking became.

Table IV

test Tensile strength 0.2 limit strain A tempe speed Schnü rature tion ( ⁰ C) (kp / mm *) (kp / mm ») (%) (%)

The electron gap number N _{v of} this alloy is calculated by substituting the above effective atomic ratios into the equation
N _v == 0.61 Ni + 1.71 Co + 2.66 Fe + 4.66 Cr + 5.66 Mo 20 rt. To 2.63.

This value is smaller than that resulting from the equation

N ₁ - max. = 2.82 - 0.017 W _Te

for an alloy with an iron content of 9 percent by weight resulting maximum permissible N ₂ value of 2.67.

The alloy is thus essentially free from embrittling phases.

The alloy was then cold-worked to reduce its cross-sectional area by 40% and then cured for 4 hours at 663 ⁰ C. Samples of the alloy were tested at room temperature, at 371 and at 462 ° C to determine their strength and ductility. The values obtained are listed in Table III below. The notch tensile strength (KZF) (notch factor K _T = 6) and the tensile strength (ZF) were measured at each of the temperatures mentioned and are given in the table as the ratio (KZF / ZF).

Table III

Rt.
Rt. 203.1
198.6 191.7
192.4 9.0
8.5 39.6
36.2 200.9 192.1 8.8 37.8 Rt. 273.2
271.5 KZF: ZF = 1.35: 1 272.3 371
371 159.3
163.3 155.0
156.2 8.0
9.0 26.7
33.3 161.3 155.6 8.5 30.0 37! 231.9
234.0 KZF: ZF = 1.46: 1 232.9 482
482 159.3 155.2
153.8 9.5
9.5 31.8
33.3 158.6 154.5 9.5 32.6 482
482 223.4
221.6 KZF: ZF = : 1.40: 1 222.5 example 11th

tensile strenght

Test temperature
rature
( ⁰ C) (kp / mm ⁵ )

0.2 limit elongation
(kp / mm) (%)

Snug
tion

Rt.
Rt.

192.9
188.9

186.0
179.8

9.5
11.0

44.4
43.8

190.9 183.2 10.3 44.1 Rt.
Rt. 266.8
267.5 KZF: ZF = 1.4: 1 267.1 371
371 158.3
160.1 153.6
154.9 10.0
9.0 37.7
34.5 159.1 154.3 9.5 36.1 371
371 225.6
228.2 KZF: ZF = 1.44: 1 226.9 482
482 144.6
142.6 141.5
138.9 10.0
11.0 33.0
37.3

143.6

218.7
210.8

214.8

140.2 10.5

KZF: ZF = 1.50: 1

35.2 Analogously to Example 1, another alloy, designated with the code J150, which had a lower iron content than the alloy of Example 10, was produced. The composition of this alloy is listed in the table below. The alloy has an electron gap number of 2.64, which is below the maximum permissible value of 2.70. The physical properties of up cold-formed into a cross-sectional reduction of 40% and then for 4 hours at 663 ⁰ C aged samples at different test temperatures are listed in Table V.

55 alloy composition

Weight percent C 0.015

Mon 7th

Cr 20.0

Co 36.2

Fe 7.0

Ni 26.0

B 0.015

Ti 3.0

Al 0.2

Nb ° ^fi

232.9

Example 12

In Table VI below are the nominal chemical compositions of three alloys listed. Alloy A is an iron-free, the teaching of the USA patent 33 56 542 corresponding alloy according to the state of the art.

table V 0.2 limit
(kp / mm ^:) strain
(%) _ test
tempe
rature
( ⁰ C) Tensile strength
speed
(kp / mm ² ) 200.0
198.5 10.5
10.5 A
Schnü
tion
(%) Rt.
Rt. 204.9
201.3 199.3
KZF: ZF 10.5
= 1.34: 1 39.1
42.9 Rt.
Rt. 203.1
382.9
392.6 166.4
169.0 10.0
9.0 41.0 371
371 387.8
169.7
169.8 167.7
KZF: ZF 9.5
= 1.43: 1 34.4
33.4 371
371 169.75
246.2
239.0 162.1
160.7 4.0
5.0 33.9 482
482 242.6
168.7
167.1 161.4
KZF: ZF 4.5
= 1.38: 1 8.6
10.0 482
482 168.0
234.2
231.5 9.3

Alloy B is an alloy according to the invention corresponding to Example 1.

Alloy C is similar to the alloy of Example 10.

The following table VII shows the physical Properties of these alloys at different temperatures after cold working up to approximately the same cross-sectional reductions and aging for 4 hours.

table VI Ni Cr Mon temperature Fe Ti Al Nb C B. Legie Co ( ⁰ C) tion 35.0 20.0 10.0 Rt. _ _ - 0.015 A. 35.0 23 19.4 9.9 371 17.3 - 0.015 0.015 B. 30.4 25.5 19.0 7.0 482 9.0 3.0 0.2 0.6 0.015 0.015 C. 35.7 Rt. table VII Aging test 371 tensile strenght 0.2 limit strain A Legie temperature Rt. lacing tion ( ⁰ C) 371 (kp / mm ^s ) (kp / mm ² ) (%) (%) 566 482 188.4 182.8 11.0 *) 46.5 A ■ 43 566 Rt. 154.7 140.6 4.0- 16.5 A. 43 566 371 154.7 148.3 3.5- 6.9 A. 43 538 482 189.1 184.2 10.0 *) 48.4 B. 50 538 189.8 150.4 2.9- 3.0 B. 50 663 191.2 183.5 10.3 *) 44.1 C. 40 663 158.9 154.0 9.5 *) 36.1 C. 40 663 143.4 140.6 10.5 *) 35.2 C. 40 663 201.1 191.9 8.8 *) 37.8 C. 46 663 161.0 155.4 8.5 *) 30.0 C. 46 663 158.9 154.7 9.5 *) 32.6 C. 46

*) Means a "crater and cone" break (ductile failure).
The remainder of the samples broke below 45 °, indicating an unacceptable level of brittleness for design practice.

Claims (1)

ι 2 to 10, characterized in that the alloy claims: is precipitation hardened after cold working. ι ν u ni · ι. * L j 19 method according to claim 11, characterized in ae- 1. (Cobalt alloy, consisting of ^ίΔ · ^vei "" ^u , ",.., ·,, · ■. ^Ö 5 indicates that the precipitation hardening in 0 to 0.05% carbon, _the temperature range of 427 to 732 C takes place. 18 to 40% nickel, _13> method according to one of claims 6 to 12, 6 to 12% molybdenum, characterized in that the alloy is before 15 to 25% chromium, _{which is} cold-worked in powder form. more than 6 to 25% iron, _{jo 14 The} method according to claim 13, characterized in 0 to 0.1% boron, characterizes the powdered alloy before 0 or 1 to 5% titanium, _the cold-deformed by pressing and sintering 0 to 1% aluminum, _inem molded body is processed.
0 to 2% niobium, Remainder cobalt,