DE1533275B1 - Process for the powder metallurgical production of hard alloys - Google Patents

Description

10 to 45% chromium,

Ibis 3.5% carbon, Obis 40% tungsten,

0 to 20% molybdenum,

Obis 10% tantalum,

Obis 5% niobium,

at least 25% cobalt and up to 10% iron or nickel,

where the sum of the molybdenum content plus the niobium content plus half the tantalum content plus half the tungsten content is in the range of 5 to 20% and where the total content of cobalt, iron and nickel is at least 35%, characterized in that the hard alloy melt is finely atomized in an inert gas atmosphere by means of a stream of inert gas and the droplets formed are quenched very quickly to fine-grain powder, whereupon the powder after filling it into a deformable metal container and hermetically sealing it at the forging temperature of a press compression until a dense material is achieved is subjected.

2. Application of the method according to claim 1 for the powder-metallurgical production of hard alloys with a carbide particle size of less than 3 μm and with the composition

0 to 8% molybdenum,

0 to 20% tungsten,
8 to 30% chromium,

2 to 4% titanium,

1.5 to 5% aluminum,

1 to 3% carbon and the remainder nickel.

3. The method according to claim 2, characterized in that the hard alloy on the composition

10 to 20 tungsten,

8 to 12% cobalt,

8 to 20% chromium,

2 to 4% titanium,

1.5 to 3% aluminum,

1 to 3% carbon and

Remainder nickel

55 is set.

4. The method according to claim 2, characterized in that the hard alloy on the composition

4 to 8% molybdenum, 15 to 20% cobalt,
18 to 30% chromium,

2 to 4% titanium,

3 to 5% aluminum,

1 to 3% carbon and ^6s

Remainder nickel

35

40

5. Application of the method according to claim 1 for the powder-metallurgical production of hard alloys with a carbide particle size of less than 3 μm and with the composition

2.5 to 15% chromium,

0 to 20% cobalt,

0.8 to 12.2% vanadium, 0 to 10% molybdenum,

0 to 20% tungsten,

0.6 to 4.0% carbon and the remainder iron,

where the molybdenum content plus half the tungsten content is greater than 4% and less than 15% and the carbon content is sufficient to give the material a Rockwell C hardness of at least 60 to harden.

6. The method according to claim 5, characterized in that the vanadium in whole or in part by one or more of the additional alloy metals

Titanium,
Niobium,
Tantalum,

Zirconium and
hafnium

is replaced, the amount of the additional alloy metals not exceeding 5% and the Sum of vanadium and the additional alloy metals is 0.8 to 12.2%.

7. Application of the method according to claim 1 for the powder-metallurgical production of hard alloys with a carbide particle size of less than 3 μm and with the composition

25 to 30% cobalt,
15 to 25% chromium,

7 to 12% tungsten,

4 to 8% molybdenum,

2 to 4% carbon and the remainder iron.

8. Application of the method according to claim 1 for the powder-metallurgical production of hard alloys with a carbide particle size of less than 5 μm and with the composition

40 to 70% tungsten carbide and the remainder cobalt.

is set.

The invention relates to a method for the powder-metallurgical production of hard alloys with a carbide phase uniformly distributed in the basic structure with a carbide particle size of throughout less than 3 μm and with the composition

10 to 45% chromium,
1 to 3.5% carbon,
Obis 40% tungsten,
Obis 20% molybdenum,
Obis 10% tantalum,
Obis 5% niobium,
at least 25% cobalt and
up to 10% iron or nickel,

3 4

where the sum of the molybdenum content plus the result is that the powder during the

Niobium content plus half of the tantalum content plus sintering, carbon can also be added

half of the tungsten content in the range from 5 to must and that nevertheless the carbon content is not

20%, and the total cobalt content can be precisely adjusted because it is the exact

Iron and nickel is at least 35%. 5 Amount of oxidized carbon not previously

The tungsten-containing alloys of the aforementioned can be determined.

Composition belong to the group of "cobalt The powder-chromium-tungsten carbide alloys described in US-PS 31 50 444" as z. B. from metallurgical operation is used for the production of GB-PS 7 98 893 are known in principle. High-speed steels with a chromium content require high-strength and high-temperature resistant hard 10%. With increasing chromium content especially in alloys, which for numerous applications beyond 10%, sintering of powder areas with extreme demands on the material properties of steel (and also of other alloys) can be used. More and more difficult, because the normally contained in the hydrogen, the production of these contents oxygen and water vapor also takes place in an alloy by pouring the melt. This causes oxidation of the metallurgical alloy components, which, however, does not affect the physical and mechanical, in particular of the chromium. This achieves the material properties that can be possible for these individual powder particles with a fine brittle alloy, namely encased oxide film that is difficult to reduce and therefore not because the casting involves at least several Powder particles to a dense minutes until solidification is required, with the consequence, 20 material obstructs. E ise η k ο 1 b (magazine "Stahl that both the basic structure as well as those therein and iron", 1958, pp. 141 to 148) has shown that distributed carbide phase is relatively coarse-grained - this is difficult with steels with high chromium contents ^; ld. A structure that is as fine-grained as possible can only be avoided if a high-purity hydrogen produced from titanium, in particular with the smallest possible grain size of the hydride, is used, the carbide phase. This is achieved by pouring the melt 25, but not with normal electrolyte hydrogen. Pure not achievable. In practice, hydrogen is used for cost reasons

Obviously out of the question for the production of hardenable steels.

(So hard alloys based on iron) is from the With the invention, on the other hand, a powder US-PS 31 50 444 a powder metallurgical metallurgical manufacturing process has already been created known, which consists in the fact that the 30 den, with the for the aforementioned hard alloy melt by means of water, steam, alloys an extremely fine-grain carbide phase, i.e. a very fine-grained carbide phase, uniformly distributed in the basic structure of nitrogen or air sprayed into fine droplets is, the droplets then by means of a liquid considerably improved grain structure and thus a are quickly quenched and the powder thus obtained optimization of the physical and mechanical then compressed, in a carbon-containing re 35 properties can be achieved, and with which the sintered atmosphere and then procedural disadvantages of the known powder mechanical - are avoided either by hot pressing or metallurgical processes. Hot rolling or by cold pressing with preceding- The method according to the invention is characterized the soft annealing - compacted up to the casting density by the fact that the hard alloy melt in a will. But even with these powder metallurgically produced inert gas atmosphere by an inert gas stream fine Steels provided are structure and thus the self-atomized and the droplets formed are very much shafts are not yet optimal. The carbide phase has to be quickly quenched into fine-grained powder, a grain size of 5 x m or more, has a un- whereupon the powder after filling into a deformation-regular Form on and is also non-uniform ble metal container and airtight sealing distributed enough in the basic structure. Furthermore, the same is also at the forging temperature of a Pressverdas Basic structure even with grain sizes in the seal until a tight material is achieved The order of magnitude of 10 μm or more is very roughly subjected to.

educated. This inadequate structure, which leads to the

a reduction of the breaking strength and the turning away coming process steps are in themselves

durability as well as the toughness of the Mate 50 known. So is from Watkinson (magazine

rials is a consequence of sintering, because during »Powder Metallurgy«, 1958, No. 1/2, pp. 13 to 23)

the normally relatively long sintering time described that an atomization of hard alloy

the individual microstructure crystals that melt in the powder by means of a water jet, but in

due to the rapid quenching of the droplets, there is still an inert gas atmosphere in the powders formed

are quite fine-grained, opportunity for growth 55 leads to slight signs of oxidation. This in

and have to agglomeration. Powders will be atomized in an inert atmosphere

tempering treatment common for steels, some of which are then compacted by sintering. That next to

Carbide particles split up again, but they remain a well-known in sintering and hot pressing

overall it is relatively coarse and they also have compression methods for metal powder, and that

also the tendency to move the powder in the hot working direction 60 by enclosing it in a metal

align. protective cover against oxidation is

In addition, however, the sintering of the powder is described by M ü 11 e r in »Eisenkolb, advances in powder

also very disadvantageous in terms of process technology. It is presented in metallurgy "(Vol. 1, 1963, pp. 326 to 328),

carried out in a hydrogen atmosphere. Now, however, not with regard to that of the invention

but commercial "pure hydrogen" always holds 85 underlying hard alloys,

still certain amounts of oxygen and water - the invention, the two known per se

steam, so that a part of the process steps contained in the alloy combining process leads to

Carbon is oxidized to gaseous oxides. extremely beneficial results. Since the through

the rapid quenching of the droplets in the powder particles is beneficial to both the matrix and the for the carbide phase adjusting small grain sizes in the subsequent hot pressing - in contrast to the well-known sintering - no longer have the opportunity for a significant coarsening, succeeds it, grain sizes of less than 5 μΐη for the basic structure and grain sizes of consistently for the carbide phase less than 3 μΐη (some

on the side, excessive mechanical processing of the workpieces is required during compaction make to break up the oxide layer so far that they reduce the strength values of the material 5 can no longer significantly impair. In the method according to the invention, therefore, is next to the extremely favorable product properties also make it easy to check the final composition of the workpiece and a problem-free

Carbide particles also turn out to be slightly larger than 3 μηα io seal of the powder given,

can, which does not bother, as long as their share in the particular with regard to the proportional

total carbide content does not have the value of about 5% high chromium content to be produced according to the invention

exceeds). The carbide phase is extremely similar to the alloys in terms of process technology

distributed in the basic structure. Advantages quite surprising, because it takes

The fact that during the compression of the 15 by no means under such an extreme oxygen powder no subsequent closure to be worked through hot pressing, as shown in the coarsening or agglomeration of the carbide phase, the fact that there is a lot of chromium for sintering even ultra-pure hydrogen is used for the process according to the invention with very high powder content important. Presumably this goes back to the fact that it should, should have been expected. True will because of the fine distribution of the carbide phase, the 20 in the method according to the invention, the danger of atomization, that at the grain boundaries cracks or bumps in the melt are caused by an inert gas stream (instead of Preparing cracks or being able to form them, far - carried out with a stream of water), but at least is avoided, so that the material is already the remaining deterrent of the atomized droplets Can be processed at temperatures that are the same or can be done in a water bath, and are even lower than the corresponding consumption in addition to the compaction of the powder processing temperatures With the conventional Le particles, only an airtight seal of the alloys. Metal containers to be taken care of, an evacuation

Such an "ultra-fine structure" is for this container, in contrast, like experiments

the alloys mentioned at the outset have so far not shown any noticeable improvement in the not known, it leads to corresponding improvements in product properties.

The method according to the invention is in its hardness combined with a high degree of toughness. In addition to the above-mentioned cobalt, there is also the fact that, as a result of the chromium-tungsten carbide alloys according to the invention, the volume of the carbide phase can be kept much larger than before with the same success for production. It was possible to use the carbon content of other alloys in the group of cobalt-based alloys with the well-known cobalt-chromium-wolf-based alloys, namely to the so-called ramcarbide alloys Values above. Accordingly, 1.5% is to be increased in the pursuit of the inventive idea, because then an extremely hard material resulted, which was almost impossible to process using the method according to the invention, which was brought into its final form during casting as early as 4 ° for the powder-metallurgical production of hard alloys a carbide particle size of less and only very slightly after casting
Extent and could only be hammered or forged with considerable difficulty. Carbon contents above 2.5% are so far in these Le-45
alloys have not been applied at all since
then no more workable results at all
let reach. In contrast, the process according to the invention allows carbon contents of up to 3.5%,
without adversely affecting the mechanical 50
see properties make noticeable.

Not only in terms of product properties,
but also in terms of process technology, the method according to the invention is very advantageous. Namely, there are kicking

no harmful oxides whatsoever, 55 brought under these and then the pressed body to a temperature

Term both the (the carbon content of the factory temperature is heated at which the cobalt component

substance-reducing) oxides of carbon than melts, whereas the tungsten carbide component

also that (hinder compaction to cast density - still remains firm. Such a manufacturing process

the) oxides of the metallic alloy components, but in no way leads to satisfactory results,

should be understood in particular of chromium. This is because the 60 during the sintering process grow

According to it, it is not necessary to reduce the carbon content of tungsten carbide particles to considerably larger ones

by subsequent carburization of the powder according to grain sizes, so that the finished product has a right

to adjust, this can rather already get with the coarse grain structure. In addition,

Melt are finally stopped. Furthermore, cobalt levels greater than about 35% during

which on the powder particles but also practically the volume of the liquid phase during the sintering process

no disruptive oxide layers that form a structural so large that the tungsten carbide particles as a result

Weakening of the compacted workpiece due to its high density already with a certain sediment

call and, if they cannot begin by reduction, begation. The large volume of the

than 5 μπι and with the composition

40 to 70% tungsten carbide and the remainder cobalt,

the hard phase being formed from tungsten carbide and the basic structure being formed from cobalt.

The well-known cobalt-tungsten carbide alloys are mainly produced by so-called »sintering with liquid phase «produced by mixing cobalt powder with powdered tungsten carbide, the mixture then by pressing into the desired shape

liquid phase also leads to the fact that the pressed body during the sintering process bulged like a barrel.

In contrast, when using the method according to the invention, it is readily possible to use cobalt-tungsten carbide alloys with a cobalt content of more than 40%, due to their ultra-fine Structure formation have excellent properties. It is expedient to proceed in such a way that Cobalt and tungsten carbide powdered separately and then compacted together to form a dense material will. Of course, a cobalt-tungsten carbide master alloy can also be atomized (i.e. powdered) and then be compacted afterwards. In both cases, the result is a very easily malleable material, which is extremely easy to work with.

“Hard nickel alloys” can also be made into specific compositions using the method according to the invention and produce them with considerably improved properties. Accordingly, the invention encompasses furthermore the use of the method according to the invention for powder metallurgical production of hard alloys with a carbide particle size of less than 3 μm and with the composition

0 to 8% molybdenum,

0 to 20% tungsten,
8 to 30% chromium,

2 to 4% titanium,

1.5 to 5% aluminum,

1 to 3% carbon and
Remainder nickel.

These hard nickel alloys to be produced according to the invention can be divided into two systems, namely in one in which the composition is based

10 to 20% tungsten,
8 to 12% cobalt,
8 to 20% chromium,
2 to 4% titanium,
1.5 to 3% aluminum,

1 to 3% carbon and
Remainder nickel

is set, and in one of the general composition

4 to 8% molybdenum,
15 to 20% cobalt,
18 to 30% chromium,

2 to 4% titanium,

3 to 5% aluminum,

1 to 3% carbon and
Remainder nickel.

Usually, hard nickel alloys (often also referred to as "superalloys") are used as high-temperature-resistant construction materials. They have good oxidation resistance and also retain very good strength values up to temperatures of approximately 980 ^° C. or in some cases even up to temperatures of 1100 ^° C.

With regard to their properties, the previously known hard nickel alloys can also be divided into two basic systems, one of which comprises cast alloys that have a low ductility and accordingly have to be brought into the final shape by casting, while the other system includes forgeable alloys which, although having a somewhat lower strength, but are more ductile and by forging or rolling in the form of z. B. have rods, plates or sheets brought in,
On the other hand, the hard nickel alloys produced according to the invention are distinguished by the fact that they are considerably stronger than the cast types, but at the same time they can also be processed very easily by forging or similar shaping processes. This favorable result is primarily due to the large amount of a thermally stable carbide phase and the fine grain size and uniform distribution of this carbide phase in the basic structure.

The previously known hard nickel alloys, and in particular the high-alloy types, normally contain only about 0.1% carbon and therefore only have a small carbide volume. The strengths of the known hard nickel alloys are therefore not due to a carbide content, but rather to a solid solution of certain alloy components such as chromium, tungsten, molybdenum and cobalt, which has a solidified effect on the nickel base. An additional strengthening results from crystals of intermetallic compounds, which contain the alloy components titanium and aluminum. These latter compounds are finely dispersed in the matrix. They can also be regarded as stable up to temperatures of approximately 980 to 1040 ^{° C.} At higher temperatures, however, they dissolve and thus lose their effectiveness as structural strengtheners.

In contrast, the hard nickel alloys produced according to the invention have a greatly increased carbon content (with, of course, a correspondingly increased proportion of carbide-forming metals), so that the carbide volume is correspondingly increased. The carbides remain stable up to temperatures of the order of 1200 ^{° C.}

As a result, they are still effective as structural strengtheners at temperatures at which the previous ones Hard nickel alloys already suffer a considerable reduction in strength (assuming can be that the strengthening effect of the carbide phase because of the ultra-fine structure formation is due, among other things, to the fact that the carbide phase is a grain growth of the Basic structure and a movement along the slip planes in the basic structure particles counteracts).

The increased temperature resistance is one of the advantages of the hard nickel alloys produced according to the invention. Another advantage is that without aging, i. H. only after cold deformation, already show excellent strength.

In addition, it is possible with the method according to the invention, even "hard alloys based on iron", i.e. to produce steels with improved properties.

Accordingly, a further aspect of the invention is characterized by the use of the invention Process for the powder metallurgical production of hard alloys with a carbide particle

509544/136

9 10

size of less than 3 μm and with the contracted alloys of this type have namely a

Settlement basic structure with a grain size of less than

2 5 to 15 Chromium V "* can P ^{m 'natürucn a} ^ ^{he AuCN eme} higher grain

o 'up to 20 ° / cobalt' size can be set in the basic structure, if in

^Ke 0.8 to 12.2% vanadium, 5f ^{5 agrees} _f ^{s Fä "s ize in} f S ^{of the smaller particle}

0 to 10% molybdenum, basic structure required, st

0 to 20 V tungsten according to the invention and its application

0.6 to 4.0% carbon and turns are shown below in the execution examples

The rest of the iron play is explained in more detail. At the same time, the

'ίο Drawings or micrographs referred to in

where the molybdenum content represents plus half of the wolverine

ram content is greater than 4% and less than 15% F i g. 1 schematically a in the invention and the carbon content is sufficient to make the material process advantageously usable at atomization to have a Rockwell C hardness of at least 60,

harden. The vanadium can be wholly or partially 15 F i g. 2 a part of the device according to FIG. 1 in

by one or more of the additional alloy - larger scale,

metals F i g. 3 a micrograph of an inventively produced

rpj _tan made tool steel, unetched, in two thousand

_Niobium fan magnification,

j _ant ^ j 30 F i g. 4 shows a micrograph of the tool steel according to FIG

Zirconium and fig. 3, but etched, enlarged two thousand times

F i g. 5 a cut image of a commercially available, m

be replaced, the amount of the additional hardened and tempered tool steel of the type

Alloy metals does not exceed 5% and the 25 M-2 magnified two thousand times,

Sum of vanadium and the additional alloy F i g. 6 a cut image of another inventive

metal makes up 0.8 to 12.2%. according to made tool steel in five hundred

In the case of »steels produced in this way with greatly increased magnification,

higher carbide phase «is the volume of the carbide phase F i g. 7 is an explanatory diagram The properties of one produced according to the invention are significantly above the conventional value increases (e.g. compared to a known steel the tool steel compared to known tool type M-2 almost doubled), at the same time of course steel,

a corresponding increase in the amount of carbide F i g. 8 one of the F i g. 7 corresponding graphic

form, predominantly of vanadium (in comparison to representation for a further inventively produced

M-2 steel up to 600%) and tool steel instead of carbon,

has found. These steels can be z. B. as work F i g. 9 a section of a commercially available Lezeug steels use, they have an improved hardness alloy with the short formula »Co with 35 Cr —17 W - and wear resistance, and they show despite 2.5 C ", cast, magnified two thousand times, the high carbide content no loss of toughness F i g. 10 a micrograph of an inventively produced and ductility, and they are also workable with the same well-warmed alloy. Settlement like the alloy according to FIG. 9 in two regards to steels specific together - a thousand fold magnification.

reduction, the invention features finally to inventive preparation of the above or by the application of the hard alloys of the invention outlined stäubungsprozeß is started with a decomposition i process for powder-metallurgical production of 45th A preferred aus-hard alloys with a carbide particle size in the form of an atomizing device is in the scheme of less than 3 μm and with the composition table in FIG. 1 and 2 shown. To operate this 25 to 30 ° / cobalt device, a batch of the Le-15 to 25 V chromium alloy to be processed (i.e. a batch with the composition required for the respective 7 to 12 / tungsten ⁵ ° end product)

4 to 8 V molybdenum ^{from z} · ^{Bp about 2} ' ^{5 kg under argon to about 110 to}

2 to 47 carbon and 160 ^c C above their melting temperature and heated

Remaining iron then via the funnel 26 into the inlet 21 above

the atomization chamber 22 poured. Within

Steels of this composition belong in the 55 of the chamber 22 becomes the group of »high-alloy steels« through the opening 21. In particular, they are initially into fine droplets especially suitable as high-speed steels and have (which as a rule a diameter of at least greatly improved properties. In particular 0.17 mm have) torn and then very quickly, they have excellent oxidation resistance and within one A fraction of a second, quenched, and - compared to the previously known 60 This is done by a stream of inert gas made of argon, high-alloy steels - an extremely high level of hardness. which enters the chamber 22 under a pressure of about 25 atm via the inlet die, in turn, at the already explained ultra-lass 23 and this via the fine structure which leaves again at the preferred outlet 28. In order to provide complete alloys of this type (e.g. in the case of an alloy quenching of the powder particles thus formed, the short formula »Fe with 27 Co - 20 Cr - 9 W - 65, there is still 6 Mo - 3 at the bottom of the chamber 22 C «) not only due to the small grain size a cooling water bath 24 into which the powder particles and the uniform distribution of the carbide phase finally fall,
pulls, but also on the basic structure. The pre- The chamber 22 has a water-cooled steel

11 12

jacket of expediently cylindrical shape. You there, as attempts have shown, an evacuation

Diameter can for example be about 90 cm and the powder enclosed in the containers none their height will be about 60 cm, but of course there will be a noticeable improvement in the properties of the end product other dimensions are also possible. The floor duct was subjected to such evacuation Chamber is slightly conical and omitted with 5 way.

a closure 25 is provided over which the container is After the closure, the container is open

a mixture of water and the fine powder particles heated to ^{forge temperature (about 1000 to 1175 0 C)}

lets pull. and for about ten minutes at this temperature

The atomizing gas is already held in front of the door. Then they turn into a mechanical one fill the molten metal into the chamber 22 in a forging plant (with, for example, a capacity of about feeds to "clean" the chamber, d. H. by around 120 kg) hammered until it becomes pancake soft Flush foreign gas residues out of the chamber. like blocks about 1.25 cm thick Only after you have a pure argon in the chamber. These blocks then warm up to one Has set atmosphere, the molten metal is rolled out thickness of about 0.55 to 0.60 cm, and poured into funnel 26. 15 in several successive rounds,

Below the opening 21 is a with each of which the block thickness by about 10% lined with high temperature resistant material. The entire reduction in thickness beKonus 27, at the lower end of which the atomization takes about 90 to 92%, based on the initial thickness Gas swept past. In doing so, it tears into the chamber before deforming.

Incoming stream of molten metal in so the container material is countless fine particles after rolling on. At the same time it cools also removed, so that the processed alloy in the form of these particles, so that the particles have already arrival of the rolled plate-shaped material ψ solidified before it falls into the cooling water bath 24th This plate-shaped material can then fall into it. This means that individual sections are divided very quickly and either quench the particles and post-treat the carbide particles or, if necessary, cannot be examined for their intrinsic metallurgical and mechanical growth to an undesired size without post-treatment.

After completion of the atomization process, Tables IA to ID are listed the mixture of water and the metal particles from practical examples of alloys peeled off the chamber 22 and dried, with 30 listed, the in FIG. 1 and 2 shown results in a fine metal powder. In practically all cases, the device is atomized and then in the fore found that 75 to 85% of the powders described in the manner according to the invention are pressed particles finer than 0.177 mm and 15 to 30% finer. Of these alloys is the are than 0.044 mm. Alloy No. 1 is a commercial grade steel

The atomization of the respective alloys to 35 M-2, while the remaining alloys are followed by a step tailored to the fine powder as the next process, the process according to the invention, the compression of these powders to a settlement, especially with regard to the content of compact material. In some cases it can contain carbon or carbide formers,
It should be advantageous to treat the powders before compaction.First of all, 40 cobalt-chromium-tungsten carbide alloys for a few minutes in a hydrogen atmosphere at around 815 to 870 ^° C. are listed in Table IA in order to achieve a gene. leads to reducing the oxide film which may be formed according to the invention. Mandatory process in this type of alloy due to the necessity of such hydrogen treatment is not extremely fine-grained and uniformly administered. divided carbide particles to a great hardness, connected

The press-compaction of the powder in forges 45 with great toughness. The size of the carbide part temperature for a compact material can be consistently less than 3 μΐη. This is very much evident from pressing or extrusion or from the comparison of the FIGS. 9 and 10 other suitable methods are used, but it is evident from the microsections given,
preferably effected by hammering or forging, FIG. 9 refers to the currently known Ko- in the following way: 50 bait tool alloys. It shows that

The powders are initially cylindrical, with the carbide particles being very large and coarse. In the container with a welded-on bottom, there is a strong contrast to the structure of the carbide filling, which consists of Inconel and a molybdenum particle in FIG. 10 relating to the invention. Have a lining so that the container material can be there, the carbide particles are very fine-grained (after completion of the forging easily removed again less than 3 μm) and also very evenly removed. Then the powders are distributed in the containers in the form of the basic structure,
pre-pressed, it being possible to use pressing pressures of about 775 to 4650 kg / cm ² due to the improved structure. Preferred F i g. 10 the mechanical properties of the way the pressing pressures are changed in the range of alloys in a very advantageous manner, between about 775 to 2300 kg / cm ² , because it was 60 For example, a typical commercial found that the higher pressing pressures in the material like that in Fig. 9 is based on most alloys, apparently because of the spherical shape a bending strength of about 158 kg / mm ² , and extreme hardness of the particles, to no significant contrast, the bending strength of the result in increased powder density. Following the F i g. 10 is more than 280 mm ² / kg. An upper lid 65 is welded into the container during the pressing process. Of course, such a strong increase in strength has been welded so that the pre-pressed powders in the containers are completely closed off from the outside atmosphere. Material made tool result.

13 14

With the cobalt-chromium-tungsten proportions of the hard, high-melting carbide alloys considered here, the carbide phase in the cobalt-based carbide phase in the particles consists mainly of carbides, and is distributed during the subsequent compression Although mainly made of tungsten carbide with a certain growth of the carbide grains instead, the know proportion of chromium carbide. When using the 5 grain size of the carbide phase, however, other carbide-forming alloy components remain very small, e.g. (namely below the upper limit of 3 μm or molybdenum and niobium, there are also carbides at most less than 5 μm), and accordingly these other components are in the Carbide phase. Also, the distribution of the carbide phase in the cobalt cell can be assumed to be nearly the same as the basic structure to be remarkably uniform. All of the cobalt remains in the basic structure, but the other alloy components in the previously described manner will be divided between the method of hammering, forging and rolling before the basic structure and the carbide phase. In the rest, preferably at a temperature of approximately 118O ⁰ C, it has been shown that the molybdenum is carried out into the.

Cobalt-chromium-tungsten carbide system is very good. Below are some of the nickel-based ones

arranges because it behaves similarly to tungsten. 15 constructed, according to the invention manufactured hard alloy

Now a more detailed explanation of the tariffs according to the table IC will be explained in more detail:

The alloys listed in Table 1B are given, which from Table 5 shows that the nickel based

Cobalt tungsten carbide. the flexural strength of the hard alloys

The cobalt-tungsten carbide alloys contain 300 kg / mm ² without the need for cold forming

besides 30 to 60% cobalt, the remainder is tungsten carbide. You can achieve 20 mung. With such flexural strength

have a basic structure made of cobalt, which can easily be used in terms of tensile strengths

Solution expect some tungsten and also some carbon 140 kg / mm ^2. In fact, the le ä

contains. In this basic structure, a phase made of alloy no. 40 has a tensile strength of about 148 kg / mm ^a "

Tungsten carbide distributed, and that when used in the hot-rolled condition, a tensile strength of

manufacturing process according to the invention in a 25 about 167 kg / mm ² after hot rolling with other

very fine and uniform distribution, with the closing aging and finally a tensile strength

Size of the tungsten carbide grains approximately in the range of about 181 kg / mm ² after cold rolling,

between 0.5 and 3 μηι, in some (less preferred- The numerical values in the preceding paragraph are

However, a value down to less than primarily applies to alloy No. 40

5 μΐη can reach. 3 ° as well as the (similarly structured) alloy No. 41. But

Tungsten carbide is made up of 6.12% carbon, even with alloy no.42.

and 93.88% tungsten combined. Accordingly, speeds of 300 kg / mm ² , so that accordingly for

the alloys considered here have tensile strengths of over 140 kg / mm ^{2 for one of these alloys}

Cobalt content of 30 to 60% and a content of are expected. In fact, the alloy

Tungsten carbide of 70 to 40% a tungsten content 35 tion No. 42 in the hot-rolled condition a tensile

measured from 65.8 to 37.6% and a carbon content of strength of 152 kg / mm ^2. Almost that

4.2 to 2.4%. Within these limits correspond to the same order of magnitude revealed for the tensile strength

The proportions of tungsten and carbon are largely the same as in alloy No. 44, which has a similar structure.

stoichiometric composition of tungsten- Finally, refer to a more detailed explanation of the

carbide (WC). Smaller fluctuations in the vicinity of 40 hard alloys according to Table 1D passed over,

the stoichiometric composition are based on iron. This alloy

With regard to the relatively high cobalt content, stanchions are preferably made after compression molding

tolerable. (according to the invention described above

The production according to the invention of the cobalt-related process) and a customary aftertreatment I

Tungsten carbide alloys can be made by subjecting them to soft annealing, deformation,

that during the first melting (i.e. before the atomization) includes hardening and subsequent tempering,

exercise process) the components in the form of the individual In Table 2 the values of the Rockwell C-

elements are united with one another. Purpose- hardness of some of the iron based hard alloys

however, cobalt is stated to be more moderate when it is melted for the first time, together with the

used together with finished tungsten carbide. 50 applied post-treatment conditions. Farther

The cobalt containing 30 to about 40% cobalt is given in Table 3 for some of those based on iron

Tungsten carbide alloys show good impact hard alloys with the values of flexural strength

strength and high wear resistance, you room temperature again.

are therefore extremely suitable as tool materials from the Le alloys listed in Tables 2 and 3 or as matrix materials. On the other hand, alloy No. 16, which contains 5% V and the more ductile cobalt-tungsten carbide alloys 1.8% C, was tested experimentally in a cutting test with a higher cobalt content (e.g. 50 From the material of this alloy, up to 60%) was manufactured to a particularly high degree as a boil-proof cutting tool that can be used for cutting construction materials. For example, a steel of the type AISI4340, which has been quenched and has an alloy of 60 produced according to the invention, ^{tempered to a Brinell hardness of 352 kg / mm 2,} 50% Co and 50% WC a flexural strength of was used. This resulted in 274 kg / mm ² . Cutting tool has a longer service life compared to a M-2 steel that is customary in all cases of cobalt-tungsten carbide-alloy steel m per minute 49 minutes (against 30 Miformly distributed tungsten carbide phase. Through the grooving in M-2 steel) and with a cutting speed quenching of the liquid particles immediately time of about 30 m per minute 14.5 minutes after atomization, relative seen, ver (about 10 minutes in the case of M-2 steel). Same-

15 16

if showed the RC-70 alloy cutting tool is only 4 minutes. At a

No. 16 at a cutting speed of approximately 15 meters per minute

30 m per minute a longer service life than a 39 minute difference in service life

those made of commercially available Τ-15 steel (4.5 minutes 10 minutes,
around 11.5 minutes). 5 F i g. 8 also shows the results of a turning

The main advantages of alloy no. 16 bank tests. There is a cutting tool from the file over a commercially available M-2 steel, alloy No. 25 with two comparison tools can be seen particularly clearly from a comparison of FIGS. 3 commercially available steels compared, in all and 4 with the F i g. 5 recognize. The in F i g. 3 and cases a steel of the type AISI 4340 as a workpiece. 4 reproduced micrographs show that the io with a Rockwell C hardness of 38 to 40 was used. Alloy No. 16 has a very fine carbide phase evenly distributed in the basic structure at a cutting speed of 30 m per minute and, for example, the service life of alloy 25 is that the basic structure itself is very fine-grained - twice as long as the service life of the commercially available ones . The carbide phase has a grain size of high-speed turning steels RC-70 or MI (namely up to less than 3 μm, and the grain size of the basic 15 22 minutes against 10 minutes),
structure extends up to 5 μm. In contrast, most of the hardnesses listed in Table ID show a commercially available M-2 steel such as that shown in FIG. 5 alloys are those with a highly increased carbide-reproduced micrograph, in the basic phase, in which a corresponding amount of structure has a grain size of more than 10 μm. Outside together with the carbon best carbiddem is the carbide does not uniformly forming the basic 20 element, namely vanadium, distributes the remaining ψ gsfüge and has also a relatively alloy components were added so that large grain size. a carbide phase in the form of vanadium carbide

Also that in FIG. 6 reproduced micrograph. The advantageous grain structure of the inven- addition of carbon and vanadium to alloys produced in accordance with the fast method should preferably be used, as in the case of the illustrative. F i g. 6 shows 25 rotating bars known, the ratio of carbon in five hundred times magnification (i.e. in the smaller to vanadium approximately 1: 4.
Scale than that with two thousand times magnification. In some more of the figures shown in Table 1D. 3 to 5) the grain structure of the alloys, the proportion of the carbide phase is still increased by alloy no. 32, namely in a sample that allows the formation of other carbides - in addition to vanadium carbide produced according to the invention and then annealed - was increased,
has been. The fine carbide phase and its identical The carbide-forming elements are not only found in the form of a distribution in the basic structure without being in the carbide phase, but also divide between others. the carbide phase and the iron matrix.

This makes it extremely difficult, and often times, to test the alloy further No. 32 a twist drill of 6.35 mm diameter 35 even impossible to establish the exact ratio beforehand. At the same time it was cast from commercially available RC-70, in which the carbon and the carbide-forming steel, the best z. Currently commercially available quick- must be added to the elements of the alloy, lathe steel, a comparative drill bit of the same geome- In the alloys listed in Table 1D it is more important Texture established. With both drills, the maximum carbon content is 3.4% and all were then in a material of the type AISI4340, 40 common the carbon content is in the range of two quenched and seen to a Rockwell C hardness of 0.6-4.0%. So the preferred ratio is -37 had been annealed, drilled holes. With nis from carbon to vanadium (or the rest The drill made from alloy no. 32 could not get 29 carbide-forming elements) in all cases be drilled while with the drill is sufficient. However, it is certain that part of the Only 17 holes are drilled in the RC-70 steel to 45 carbon with the carbide-forming elements could. Then there was such a strong edge wear of a hard carbide phase that a hard carbide phase and also significant edge chipping, so that the lower part of the carbon in the iron matrix further drilling with this material no longer passes. This hardens the basic iron structure could become. In contrast, the bar showed and is thereby made up by the usual hardening process Alloy No. 32 brought a Rockwell C hardness of at least 60 even after boring out 50. 29 holes still have no splinters or fractures to the strong excess of carbon (over the to the Edges, which proves its toughness. carbon consumed for the aforementioned purposes

The F i g. 7 and 8 illustrate the over- all) can either lead to the formation of further carbide inferiority of the alloy phases produced according to the invention lead or else to the fact that after the heating Compared to the comparable known Le treatment, there is an excessive amount of austenite in the basic structure alloys. remains behind. Both may be undesirable.

F i g. 7 graphically shows the results of a rotary The concentrations of tungsten and molybdenum bank tests for an alloy no. 32 made in accordance with the present invention Tool compared to three hand-made hard alloys based on iron so one on top of the other comparison tools made from common steels. 60 based that the total content of molybdenum plus the As a workpiece, a steel half the tungsten content was greater than 4% but less in all cases is of the AISI 4340 type with a Rockwell C hardness greater than 15%. The molybdenum content fluctuates from 50 to 52 edited. It was found that the alloy was 0-10% and the tungsten content was 0-20%. at No. 32 of the currently best alloy, namely the L-high tungsten content is little or no alloy RC-70, is far superior. For example, the alloys contain a proportion of molybdenum. on sitting at a cutting speed of 18 m per the other side can have a high molybdenum content Minute the alloy 32 lead to a service life of 17 mi, no tungsten at all to the alloys utes while adding the service life in comparison.

The chromium content of the alloys is 2.5 and if greater oxidation resistance is desired is, the chromium content approaches the upper end of the aforementioned range.

Cobalt is an optional addition to the alloys. This element has a solidifying effect on the solid Solution of the individual alloy components in one another. Its addition leads in particular to an improved Strength at elevated temperatures

Cure temperatures below 920 ⁰ C, while the commercially available high-speed turning tools for curing temperatures considerably require more than HOO ⁰ C if they are to be brought to a Rockwell C hardness of 70th The lower hardening temperatures lead to the advantage of reduced scale formation.

In addition to the values given in Table 4, it should be added that an ^{annealed at 1010 0} C,

Vanadium is the most important alloys, then quenched and then tempered twice at 496 ° C.

carbide-forming element. It can be completely or partially replaced by the also strongly carbide-forming elements titanium, niobium, tantalum, zirconium and hafnium. The use of these other carbide formers, individually or in combination with one another, is optional. When they are used, the vanadium content is in the range from 0 to 12.2% and the content of Ti, Nb, Ta, Zr and / or Hf in the range from 0 to 5%, with the additional requirement that the total content of the tempered sample (despite of a crack) showed a Rockwell C hardness of 71 and a breaking strength of about 15 kg / mm ^2. In terms of Vickers value, this sample had a hardness of more than 1,100 and its Rockwell A hardness was about 88.

In addition, alloy No. 36 is excellent in oxidation resistance. In the treatment a sample of this alloy compared to a sample of the commercial high-speed steel from

of vanadium and the other carbide formers at least 20 type RC-70, i.e. the best currently available

is at least 0.8% and not more than 12.2%.

The post-treatment that is still useful for the iron-based alloys considered here and that follows press compaction in the manner customary for tool steels consists in the first stage of soft annealing at temperatures between 815 and 870 ^° C., followed by slow cooling, e.g. . B. in an oven. This makes the material sufficiently soft to be able to deform. After molding, the material is cured again in a conventional manner ( "austenitizing"), namely in that it is first heated to a temperature of about 1150-1210 ⁰ C, then a sufficient time (until an adequate "solution" of the Henden high speed steel , in air at elevated temperature the following weight gains resulted:

material

Weight increase in mg / cm ²

168 h at
about 650 ⁰ C

24 h at
about 730 °

4 h at
about 815 ⁰ C

RC-70
Alloy 36

28.4
1.7

5.5

42 4th

Finally, the edge retention of alloy No. 36 on an AISI steel

Carbide in the basic structure) was examined on this 35 4340 with a Rockwell C hardness of 42. The service life of a corresponding tool is dipped in oil or by cooling in air at a cutting speed of 18 m per quench. After quenching, the Mate minute is about 28 minutes, at a Schneidgeschwinrial then through a single speed of 24 m up to two hours heating at per minute about 12 minutes and temperatures near 510-600 ^0C getem- 4 ° at a cutting speed of 33 m per mipert. This annealing can be done two or three times
be carried out (with one cooling down each time
Room temperature between consecutive
Annealing processes) to give the material an additional
To give toughness.

It should also be pointed out that during annealing, hardening and also tempera the Material is not heated to such temperatures that an impermissible coarsening or agglomeration the carbide phase can occur.

The properties of material no. 36 (as an example of a high-alloy steel) should be discussed in particular. This material is expediently according to the invention at a temperature of about 1180 ⁰ C for about 15 minutes.

Table IA

Composition of the hard alloys of the cobalt-cobalt-chromium-tungsten carbide type produced according to the invention (In all cases including the usual impurities).

Alloy no.

Chemical composition in percent by weight
(Remainder each cobalt)

55

26 34 35

compressed according to. In spite of its high content of alloy components, the powder can easily be forged and rolled out into a sheet about 3.8 mm thick without any significant breaks at the edges. The carbide volume is relatively high, and the size of the carbide particles is less than 3 μΐη (after 60 compression at 1180 ⁰ C).

The Rockwell C hardness of alloy No. 36 (as well as all alloys with a similar composition) is above 70, i.e. H. above the upper hardness limit, which was previously available for commercial high-speed steels 65 or die steels has become known. In addition, alloy No. 36, as can be seen in individual from Table 4, already with "Tantung - G" - a commercially available one

Alloy with approximately

30% Cr 15% W 2.5% C

"Tantung - 144" - a commercially available one

Alloy similar to No. 7

17.5% W 35.45% Cr 2.05% C

17.5% W 35% Cr 2.5% C

10% W 7.5% Mo 35% Cr 2.5% C

32% Cr 17% W 3% Fe 2.5% Ni

2.5% C

16.5% W 3% Mo 31% Cr 2.9% Fe

2.4% Ni 2.4% C

17% W 35% Cr 3% C

10% W 35% Cr 5% Mo 2.5% C

15% W 35% Cr 4% Nb 2.5% C

27.5% W 25% Cr 2.5% C

38.5% W 14% Cr 2.5% C

Table IB

Table ID (continued)

Composition of the hard alloys of the cobalt-tungsten carbide type produced according to the invention (In all cases including the usual impurities).

Alloy-chemical composition in percent by weight No. (remainder in each case Esen)

Alloy Chemical composition in percent by weight run /? No.

50% toilet
47% W
56.4% W

50% Co
50% Co
40% Co

3% C, 3.6% C

Table IC

Composition of the hard alloys produced according to the invention based on nickel (in all cases including the usual impurities).

Alloy Chemical composition in percent by weight No. (remainder in each case nickel)

40 12.5% W 10% Co 10% Cr 3% Ti 1.5% Al 1.25% C

41 15% W 10% Co 15% Cr 3% Ti 1 5% Al 2 / C

42 16.8% Co 20.75% Cr 5% Mo 3.25% Ti 3.72% Al 1% C

43 14.4% W 9.6% Co 16.63% Cr 2.9% Ti 1.5% Al 2.49% C

44 15.6% Co 26.5% Cr 4.6% Mo 3% Ti 3.43% Al 2% C

21 Same as alloy no. 15, but the powder

treated in a hydrogen atmosphere and sealed in evacuated containers. 22 6.5% W 4% Mo 4.5% Cr 5% Co

10% V 2.35% C

23 6.5% W 4% Mo 4.5% Cr 5% Co 10% V 2 75% C

24 6.5% W 4% Mo 4.5% Cr 5% Co 10% V 3.15% C

25 2% W 8% Mo 4% Cr 8% Co 5% V 2% C

27 6.5 °% W 4% Mo 4.5% Cr 5% Co

10% V 3.4% C

28 6.5% W 4% ° Mo 4.5% Cr 5% Co

6% V 4% Ti 3.4% C

29 5% W 6% Mo 4% Cr 12% Co 8% V 3% C

30 4% W 5% Mo 15% Cr 8% Co 8% V 2.85% C

31 8% W 9% Mo 6.5% Cr 18% Co 3.5% V 1.8% C

32 9% W 6% Mo 7% Cr 8% Co 8% V 2 5% C

33 8% W 5% Mo 12% Cr 15% Co

70 / γ 25% C
36 9% W 6% ° Mo 20% Cr 27% Co 3% C

(b) Differs from No. 16 only in the size of the atomized particles.

40 table

Table ID

Rockwell C hardness for some of the in Table 1D listed hard alloys based on iron

Composition of the iron-based hard alloys produced according to the invention (in all cases ^4S including the usual impurities).

Alloy Chemical composition in percent by weight No. (remainder in each case iron)

Alloy hardness hardness hardness after 2 times 2 h tion No. tempe- after tempering temperature ° C to quenching

538 ° C 565 ° C 582 ° C

1 6% W 5% Mon 4% Cr 1.25% C 4.2% Mo 3.2% 4% Cr 2% V 0.8% C V 1.4% C 10 55 11th 60 15th 6g 17th 1190 67.8 62.0 62.9 61.9 2 6% W 5% Mon 4% Cr 5% W 4% Cr 6% V 1.1% c 1.7% C 1204 68.6 63.8 64.1 63.2 3 6% W 5% Mon 4% Cr 1.7% C 5% Md 4% Cr 9.1% V 1.5% C % Cr 5.25% V 1.7% C 16 1218 68.6 64.6 66.7 63.9 4th 6% W 5% Mon 4% Cr 6% W 5% Mon 4% Cr 12.2% 1.55% C 1232 66.0 64.0 65.0 64.0 1.8% C 6% W 5% Mon 4% Cr 1.8% C 1160 63.7 61.1 63.3 60.0 5 5.5% W 4.7% Mo 3.6 ' 6% W 5% Mon 4% Cr Cr 4.7% V 1.8% C 1177 63.9 63.1 64.9 63.0 6% W 5% Mon 1190 63.8 63.5 63.2 63.1 6th 6% W 5% Mon 5% V 1204 61.5 62.0 61.5 58.0 6% W (b) 5% V 1204 64.4 62.2 60.5 - 9 1.8% C 5% V 1232 65.5 63.9 62.5 - 10 5 ° / " V 1177 66.0 64.1 65.3 - 11th 5% V 1190 64.6 - 67.0 - 15th 5% V 1204 63.7 66.9 66.1 - 16 1177 64.3 66.9 67.0 - 17th 1190 62.1 - 67.0 - 1204 60.8 66.5 66.8 -

Table 2 (continued)

Alloy hardness after hardness

tion no. temperature to deter- ⁰ C

Hardness after tempering twice for 2 hours

51O ⁰ C 524 ° C

538 ° C

565 ⁰ C

22nd 1190 63.1 - 1218 63.2 - 23 1190 68.1 - 1218 68.8 - 24 1190 69.0 68.1 1218 69.1 68.7 25th 1190 67.8 68.1 1218 67.7 68.5 27 1190 71 71 1218 71 70 28 1190 71 71 1218 70.5 71 29 1149 70.6 70 (496 °) 1177 70.5 70 (496 °)

30 1149 64.4 65 (496 °) -

1177 64.5 65 (496 °) -

31 1065 68.2 70 1121 68.2 70 1177 67.5 70.5 1204 66.4 70.5 32 1177 65.1 68 1204 67 69.3 1232 67 69 33 1065 64.6 66.4 1121 65.1 66.8 1177 65.1 67.8 1204 65.0 67.1

62.8 61.8 - 61.0 66.1 65.0 67.1 64.1 67.2 - 69.0 - 67.5 - 68.7 - 70 71 - 70 71 - 69.5 (551 °) - 70.5 (510 °) - 70 (551 °) 64.5 (510 °) - 63.4 (551 °) - 65 (510 °) - 69.5 (551 °) - 70 - 70 69 70.5 67.0 - 67.0 -

Table 3

Bending strength (at room temperature) for some of the ones listed in Table 1D

Iron-based hard alloys

alloy Hardness tempe Tempering Time hardness Bending failure No. temperature ° C temperature ⁰ C h Rc strength
kg / mm * 16 1190 565 4th 66.0 263 16 1190 565 4 + 4 64.1 350 17th 1190 565 4th 64.8 254 17th 1190 565 4 + 2 67.1 244 25th 1218 538 2 + 2 70 224 29 1177 524 2 + 2 70.5 222 30th 1177 524 2 + 2 65 347 31 1177 510 2 + 2 71.5 197

Table 4

Rockwell C hardness of alloy No. 36 (Table ID)

(Fe with 27 Co - 20 Cr - 9 W - 6 Mo - 3 C)

Alloy hardness-hardness after hardness after tempering twice for 2 hours

No temperature ⁰ C quenching

496 ⁰ C 510 ° C 524 ° C 551 ° C

900 61 63 - 61.5 927 65.7 - 71 - 955 67 71 71 982 67 - 71 - 1010 67 71.5 - 71 1038 66 70.5 - 71 1150 58 60 60

60

Table 5

Bending strength (at room temperature) for some of the hard alloys listed in Table IC with a nickel base

alloy Hot rolled Bending strength No. in kg / mm ² Aged 100 h at 733 ° C 40 304 316 41 298 283 42 276 300 43 264 248 44 245 254 In addition 6 sheets of drawings

509544/136

Claims (1)

10 claims: 1. Process for the powder metallurgical production of hard alloys with one in the Basic structure uniformly distributed carbide phase with a carbide particle size of throughout less than 3 μm and with the composition