DE19525983A1 - High heat-resistance nickel@-based alloy - Google Patents

Abstract

High heat-resistant Ni-based alloy having a structure which has been subjected to tempering comprises: an MC-type carbide phase in 0.02-1.5 atom % from 2(C) amt., where (C) is atom % C.; a gamma'-phase of 10-30 atom % calculated from 4(0.026 (Cr) + 0.13 (Mo) + 0.13 (W) + 0.6 (Al) + 0.68 (Ti) + 0.5 (Nb) + 0.5 (Ta) - (C)), where each bracketed element is an amt. in atom % and non-loaded elements are calculated as zero; alpha-W-phase in amt. of 0.5-30 vol.%; and balance of Ni-contg. austenitic phase. Prodn. of the alloy is also claimed. The alloy is tempered at 600-850 deg C. once or twice for at least 3 hrs.. The alloy has a surface binder structure, after treating at 700-1000 deg C in atmospheric air, consisting of 3 layers of outer oxidised Cr-contg. layer, a granular alpha-W layer, and an inner oxidised Al- and Ti-contg. layer on one side. The alloy consists of 0.002-0.15% C, up to 2% Si, up to 3% Mn, > 10-25% Cr, 10-30% W, up to 15% Fe, 0.4-2.5% Al, 0.4-3.5% Ti, and balance of Ni and unavoidable impurities. A part. of the Ni is pref. replaced by up to 3.0 wt.% Nb and/or up to 3 wt.% Ta, esp. up to 10 wt.% Mo, more esp. up to 0.2 wt.% Zr and/or up to 0.02 wt.% B.

Description

The invention relates to a highly heat-resistant nickel ba sis alloy, for hot or hot working dies mainly in a warm or hot temperature range of 900 ° C or below can be used, and for hot strand pressing tools or parts for Cu and Al or their alloy is used.

According to a recent trend in the common use of Sharing and reducing the number of steps in the process Automotive industry there was a need, the service life to improve a hot or hot deformation shape, which is used for Forming automotive parts, such as. B. crankshafts and  Crank rods for motor vehicles is used. However became the need described above in one case of a hot forming tool steel designated SKD61 not necessarily satisfied. Further one will be high heat-resistant Fe-based alloy, such as B. A286, and a Inconel 718 alloy for hot extrusion tools for Cu and Al or their alloys are used and it is one Reduction in manufacturing steps, what reduction achieved by improving the tool life is also desired.

In addition to these, highly heat-resistant nickel-based alloys than in a high temperature range of around 1200 ° C used hot forming tools, such as. B. piercing pins and Mandrels used to make seamless tubes the, in JP-OS 3-61345, and as an isothermal forged metal mold at high temperatures from 1000 ° C to 1150 ° C used in air disclosed in JP-OS 4-41641.

Further are those, for example, in the Japanese patent publications 54-33212, 60-58773, 58-502 and 56-21061 Alloys described, although they are of those of the ing invention have different purposes than high heat resistant alloys based on Ni-Cr-W known.

The suitability for hot forming, an excellent Zer Machinability, a high yield strength and toughness in space temperatures, excellent hot sliding properties in a temperature range as high as 700 to 900 ° C and wear resistance and resistance to hot cracking with hot forming, the shapes are or hot use or the extrusion tools for Extrusion of Cu and Al or their alloys is required does.  

Regarding the improvement of the hot sliding ability and the Hot wear resistance requires both a tight Adhesion as well as stability of an oxide film and high yield point. However, softening with a hot heat forming tool steel of a conventional SKD61 class Tempered martensite and temperatures exceeding 700 ° C ter reducing the high temperature yield strength, and it is impossible due to a low amount of Cr in the steel superior in terms of tight grip and stability Form oxide film, so that there is an early wear due to direct contact between deformed materials and Tools results and finally a seizure gently.

On the other hand, both a reduction in thermal expansion expansion coefficient as well as a high yield strength at ho hen temperatures to improve the hot crack resistance needed. However, it has a highly heat-resistant iron base yaw, such as B. A286, a high coefficient of thermal expansion ent, and a γ phase, which is a precipitation hardening phase is converted into an η phase, which is a sta bile phase in a temperature range exceeding 700 ° C is because the γ'-phase from a mainly from Ni₃Ti be standing composition is what is causing the Problem causes the high temperature strength to decrease becomes.

Excellent machinability is required for hot forming tools, but have highly heat-resistant Le Alloys like A286 the error that their machinability all common to those of martensitic materials in a white inferior extent.

There have been several highly heat-resistant nickel-based alloys gene proposed for hot forming tools. Example  the alloys disclosed in JP-OS 3-61345 are wise insufficient in terms of oxidation resistance and have insufficient wear during hot forming constancy. Furthermore, they were open in JP-OS 4-41641 bared alloys the problem that the hot sliding is insufficient at a high sliding speed because the alloy for use in an isothermal forging mold is determined.

With any of the high heat resistant described above Ni-Cr-W nickel-based alloys are assumed to be are intended to be used in a very high temperature range heat resistance and high at around 1000 ° C Creep resistance as the main goals. Accordingly has each of the conventional heat-resistant, one considerable amount of W-containing nickel base alloy against high temperature creep resistance, which is determined by solid solution strengthening of W is increased, and is not sufficient for high strength at 700 to 900 ° C and an improvement in hot sliding, wel che two properties by the present invention be aimed for. Accordingly, it was very difficult to get them on Application areas to be used by the present Invention are intended as far as their properties be be hit.

In view of the problems with these hot working tool steels and highly heat-resistant iron-based and The inventors dealt intensively with nickel-based alloys with the development of a new material that will become Hot forming and to improve the oxidation resistance speed, the high temperature resistance, the thermal expansion coefficient efficient and machinability for the purpose of replacing the conventional hot forming tool steels through the new Material as one of the main purposes. This led to  Invention of a highly heat-resistant nickel-based alloy which as its main phase contains mainly Ni Phase, the W in the solid solution state up to its Contains fixed solution limit. The new alloy will by finding an optimal salary range both ei ner γ'-phase, which mainly contains Ni₃ (Al, Ti) and is excreted by an occasional treatment, as well as egg ner solid solution of W (α-W) and a primary carbide from MC type possible, one required by the hot forming tool excellent hot gliding ability, one when hot shapes required wear resistance and a hot crack resistance as well as resistance to oxidation chen. It was also newly found that under the new Legie With this structure, the alloys in which the Building one at high temperatures in atmospheric air high temperature generated surface scale at least three layers of an outer, mainly Cr contain tendency oxidized layer, a granular α-W layer and an inner oxi, mainly containing Al and Ti dated layer in this order from the surfaces has the close adhesion of an oxide film can improve and improve a high temperature Resistance to oxidation and hot sliding own.

As from the assembly requirements of the first shown below and to understand second aspects of the invention the characteristics of the highly heat-resistant nickel-based alloy according to the invention not only on the alloy together setting, but also on other characteristics. And that is a significant difference between the high heat resistance the nickel-based alloy of the invention and the conventional one Chen highly heat-resistant, W-containing nickel-based alloy stungen that the alloy according to the invention has a structure has undergone an occasional treatment, which Ge  add is characterized by a γ′-phase. Invention Ge The tempering treatment is carried out at 600 to 850 ° C leads. In a case of about 1000 ° C or more, as in conventional high-temperature resistant nickel-based alloys used, an occasion that has been eliminated changes hardened phase at the temperature of about 1000 ° C or about a solid solution, so that it is in the state of Technology was assumed that the previously performed An treatment itself was useless, and its importance was practically not recognized.

According to the invention, one is eliminated by tempering Phase that occurs with conventional high-temperature resistant nickel ba do not use alloys with similar compositions was used positively. The structure is accordingly the highly heat-resistant nickel-based alloy according to the Er invention characterized in that as much γ′-phase as 10th up to 30%.

Thus, according to the first aspect of the invention, a high heat-resistant nickel base alloy in a tempering treatment structure subjected to the development, the 0.02 to 1.5% carbide as the amount of carbides of an MC type, which amount as At .-% is calculated from a formula (1), 10 to 30% γ ′, which is calculated as At% from another formula (2), and 0.5 to 30% by volume of α-W expressed as% by volume has, the rest of a mainly Ni containing au stenitic phase is:

2 [C] (1)

4 (0.026 [Cr] + 0.13 [Mo] + 0.13 [W] + 0.61 [Al] + 0.68 [Ti] + 0.5 [Nb] + 0.5 [Ta] - [C]) (2)

elements that are not added are counted as zero and each element in parentheses, at% of each element means.

According to the second aspect of the invention, the problems of seizure and oxidation solved in the Use during hot or hot sliding. The inventors have contributed to various alloys high temperatures formed in atmospheric air that regarding many alloys including the high heat-resistant nickel-based alloy after tempering examined according to the first aspect of the invention. As a result, the inventors found that it was for a material with superior seizure resistance is optimal when used in high temperature gliding, a Alloy to be used by a tempering treatment eliminated γ'-phase, which also contains W and which is provided with a surface scale that one Has structure with a granular α-W layer, which is between an outer, mainly containing Cr oxidizing th layer and an inner, mainly Al and Ti ent holding oxidized layer.

According to the second aspect of the invention, one is high heat-resistant nickel-based alloy is provided in the a matrix of a structure subjected to an annealing treatment which structure has an Au containing mainly Ni stenite phase, the alloy with a high Temperatures formed in atmospheric air chenzunder is provided, of at least three layers an outer, mainly Cr containing oxidized Layer, a granular α-W layer and an inner, mainly in Al and Ti containing oxidized layer in this order from the surface side.  

The highly heat-resistant nickel base is preferably present gation suitable for realizing the invention, essentially by weight from 0.002 to 0.15% C, to up to 2% Si, up to 3% Mn, <10% to 25% Cr, 10 to 30% W, up to 15% Fe, 0.4 to 2.5% Al, 0.4 to 3.5% Ti and Rest Ni and accidental impurities.

Even more preferred can be in the alloy composition Part of the Ni by up to 3.0 wt .-% and / or up to 3.0 % Ta by weight. Further, in addition to that composition described above, part of the Ni to be replaced by at least one from the up to to 10% by weight Mo in a range from W + 2Mo30, up to 0.2 % By weight Zr, up to 0.02% by weight B, up to 0.02% by weight Mg and up to 0.02% by weight of Ca group is selected. At the alloy elements described above can be any the additional one added to replace a portion of Ni Elements selectively in all possible combinations be set. In addition, the selectively added ele elements of the given formula of the γ′-quantity shown above are enough.

The function of the high heat resistant nickel base alloy of the invention prescribed structure is in following explained.

An MC type primary carbide is the hardest phase in the high and heat-resistant nickel-based alloy of the invention a function that would coarsen austenitic grains rend hot forming to produce the alloy suppress, and another function to improve egg hot gliding ability in operation. As for the amount of MC carbide concerns, assuming that all quantities added C’s are present when combined with Ti, Nb and Ta Double the amount of C, expressed as At%, as the content  be considered on the MC type carbide. Is accordingly the MC type carbide amount described above is a value that is calculated by 2 [C] of formula (1), in which the [C] At .-% means carbon. To the effect of this MC type carbide To achieve a must at least 0.02 at .-% over MC amount in progress, but a 1.5 at.% The chain structure of the MC-type carbide that starts at the starting point of heat cracks with the The result is that the tool life is reduced. Accordingly, the amount of MC type carbide calculated as at% added in an amount of 0.02 to 1.5%. Preferably the MC type amount of carbide is 0.1 to 1.0 at%.

The elimination of a γ'-phase by an annealing treatment is the most effective at improving strength Room temperature and at high temperature. The basic together settlement of the γ'-phase is represented by Ni₃Al. In a an alloy containing a plurality of elements are each but different added elements actually in one Solid solution state at the Al site of the γ′-phase. It is very difficult to measure the excreted amount of this γ′-phase sen. Accordingly, both the Compositions as well as the ratio of the γ phase and γ'-phase in Example 1 described later chose alloy No. 5 of the invention measured, and under Use of these measured values and the known values (Hiroshi Harada and Michio Yamazaki: "Alloy design for γ ′ precipitation hardening nickel-base superalloys containing Ti, Ta and W ", Tetsu-to-Hagane, Vo. 65 (1979), p. 1059) a coefficient is obtained for the respective elements are in solid solution in the Al site of the γ′-phase. With Auswer tion from the composition range of the alloy of the Er Cr, Mo, W, Ti, Nb and Ta are found as elements seeks that gelan in the Al place of Ni₃Al in solid solution What Sample No. 5 concerns in Example 1, each  but no coefficients of Mo and Ta are calculated, because sample No. 5 a Zu containing neither Mo nor Ta composition. Accordingly, what are the coefficients of Mo and Ta taking up Al positions in the γ′-phase, the coefficients of W and Nb used in the same Chen groups like Mo and Ta belong.

When calculating them, it was assumed that with respect to Ti, Nb and Ta residues after formation of MC-type carbides by verbin with the total amount of carbon added to the Contribute to the equilibrium of a γ-γ′-phase. From the calculations results will be the total amount in the Al-Platz of the γ'-phase elements present regarding the added Elements were determined, and a fourfold amount thereof was determined assumed as the calculated γ′-quantity. The γ'-quantity at Invention is thus calculated from the following equation which corresponds to formula (2) described above:

calculated γ ′ = 4 (0.026 [Cr] + 0.13 [Mo] + 0.13 [W] + 0.61 [Al] + 0.68 [Ti] + 0.5 [Nb] + 0.5 [Ta] - [C])

(the elements in [] express the atomic percentage of each el elements, and non-added elements are considered zero expected).

Then the highly heat-resistant nickel-based alloy tion of the invention of a heat treatment for excretion subjected to the γ'-phase. This heat treatment will a solution annealing treatment for homogenizing an after Heat deformation obtained structure and for temporary order conversion of the excretion into a solid solution leads. Temperatures for this solution heat treatment are preferably in the range of 900 to 1200 ° C. Temperatures below 900 ° C make the excretion convert into a solid solution insufficient, and temperatures above 1200 ° C  coarsen the grain size, what about strength and the hot crack resistance is disadvantageous. In the case where one Strength at room temperature is important, a Lö solution annealing treatment at lower temperatures leads or for the purpose of leaving tension, which at Forging occurs, can be omitted.

Then a tempering treatment is carried out, and this tempering treatment is in order to excrete the γ'-phase the highly heat-resistant nickel-based alloy and to increase High temperature resistance is essential. The occasion act is preferably at temperatures from 600 to 850 ° C carried out. Require temperatures below 600 ° C a long period of time to excrete the γ'-phase, and Temperatures exceeding 850 ° C coarsen the temperature separated γ′-phase or do not excrete a γ′-phase because it remains in solid solution, so that it is not sufficient High temperature strength is obtained.

This tempering treatment can be carried out once or twice and the duration of treatment should be total be at least 3 hours or more.

If the above-mentioned calculated amount of by the An let treatment eliminated γ ′ below 10%, the High temperature resistance, which means a reduction in the resistance resistance to hot wear and hot sliding acts, resulting in a reduction in tool life results. On the other hand, the 30% exceeding be calculated γ ′ quantity the high temperature deformation resistance and makes hot forging difficult. Accordingly, the calculated by the equation described above γ'-amount in a range of 10 to 30%, preferably 13 up to 25%.  

The above-mentioned in Japanese Patent Publ 54-33212, 60-58773, 58-502 and 56-21061 Alloys have the purpose of solidifying the solid Solution by adding W and hardly contain γ'-forming Elements. Or it will, even in a case where the γ'-forming Items in small quantities, none let treatment performed so that no solidification with the γ'-phase is obtained. Since the temperatures at Using the conventional alloys be about 1000 ° C wear, namely during use the γ'-phase in the solid solution converted. In the case of this known Le alloys is what the functions of Al, Ti and Nb be hits, which are γ′-phase formation elements, then Al acts for example to improve the oxidation resistance speed, and Ti and Nb act to improve the strength carbide formation, d. H. it will be in opposition no solidification in the case of the present invention aimed at using the γ'-phase, and its purpose is completely different from that of the present invention.

Next, because with the known, in these Publi Alloys disclosed a high temperature creep resistance at around 1000 ° C is considered important, the alloys in a state after solution treatment Temperatures of 1200 ° C or above or in another Condition used where the alloys are again at 1080 ° C or higher after the solution heat treatment, so that the grains are coarsened and the alloys for a use are disadvantageous, the strength and requires a hot crack resistance at 700 to 900 ° C, which use is sought with the invention.

Next is an evenly distributed α-W phase (the fixed Solution of W with a bcc structure) one for the alloy important alloying phase of the invention. The  α-W phase not only contributes to a reduction in heat elongation coefficient of an alloy, but prevent there is also a seizure when the legie tion under hot gliding is used. The delivers further α-W phase an effect of improving close adhesion an oxide film described below. This effect The α-W phase, if its quantity, results from measurement obtained with an image analysis, 0.5 or more vol .-% be wearing. A volume percentage exceeding 30% gently reduces the oxidation resistance and egg ner hot formability, and therefore the content of the α-W phase in the range from 0.5 to 30% by volume, preferably 3 up to 20 vol .-%.

The highly heat resistant nickel base alloy of the invention is characterized in that the γ'-phase and the α-W phase available at the same time. This feature of the invention has been used in conventional high-temperature resistant alloys never found.

The γ'-phase is in conventional high heat resistance gene alloys of the γ′-precipitation hardening type na of course, but there is no α-W phase.

With conventional high-temperature resistant nickel-based alloys alloys with a high W content have a possibility that the α-W phase is present in it, but the purpose is α-W phase an effect for excretion of the small amount of which only at the grain boundaries or in grains around which Improve creep resistance, and is of their function and effect clearly distinguished in the invention. Wei ter the alloy of the invention differs significantly of these conventional alloys by adding to the conventional ones Lichen alloys, as described above, no γ'-phase is present. In the alloy of the present invention  it the simultaneous presence of both the γ'-phase as also possible for the first time in the α-W phase, the Eigen requirements, such as B. strength, hot sliding resistance, hot abrasion and hot crack resistance and oxidation resistance at 700 to 900 ° C at the same time.

Furthermore, the highly heat-resistant nickel-based alloy of the invention is characterized in that the structure of a surface scale formed at high temperatures in atmospheric air has at least three layers, the outer, mainly containing Cr, the oxidized layer, the granular α-W layer and the inner, mainly Oxidized layer containing Al and Ti in this order from the surface side, as shown in FIG. 1 in Example 1, for example. The mechanism of the formation of this oxide film is not clear. If the oxide film structure does not have at least the three layers, the close adhesion and the oxidation resistance of the oxide film deteriorate.

If, for example, α-W grains with a dimension above 5 µm on the surface will be exposed the parts of the oxide film formed from WO₃, which is not sufficient has close liability. However, since the total amount of α-W is controlled to 30% or less, it will not primary factor than that of a tool life highly reduced. It is appropriate that a kör few α-W phase in the scale, which phase by a different α-W phase is formed, a particle dimension of 1 µm or less. This is the preferred structure ge of the surface scale obtained when the Le gation of the invention is heated in atmospheric air, at least three layers, the outer, mainly Cr contained oxidized layer, the granular α-W layer and the inner one, mainly containing Al and Ti, oxidized  Layer in this order from the surface side exhibit.

Further in the alloy of the invention, apart from the types of MC-type carbide in the amount described above, the γ'-phase, the α-W phase and the accidental Verunreini the rest of them contained an austeni mainly containing Ni table phase. The matrix of the alloy has a high solid Solubility for W and high high-temperature strength. Next are the solid solution and the elimination of the γ'-phase in the area described above in the case of a main Ni-based nickel-based alloy possible.

It is supposed to be the function of the individual, in the high heat permanent nickel-based alloy containing the invention Elements for carrying out the invention described above to be discribed.

C is added which, in addition to a function as deoxidizing element, additional connection functions with Ti, Nb and Ta to form stable MC-type primary cards bide has to coarsen austenitic grains during suppress a hot deformation and the hot glide ability to improve. The effect of the C is achieved in to which you add at least 0.002%, yes its excessive addition of more than 0.15% makes that Chain structure of the MC type carbide and causes the first hot cracks emanating from this part, so that the tool life is reduced. Accordingly, C in an amount of 0.002 to 0.15% by weight, preferably 0.01 added to 0.07 wt .-%.

Si is added as a deoxidizer and is effective at the same time to improve the tight adhesion oxide film. However, this causes excessive addition  a reduction in both hot working of more than 2% availability and ductility at room temperatures. The according to Si in an amount of 2% by weight or less, preferably 0.7% by weight or less added.

Mn is added as a deoxidizer. Its excessive Additive that exceeds 3% causes a reduction tion of high temperature strength, and therefore Mn becomes in egg an amount of 3% by weight or less, preferably 1% by weight or less added.

Cr forms an oxide film with extremely tight adhesion on the surface of an alloy during heating to high temperatures and improves the oxidation resistance efficiency. In addition, Cr can also improve hot sliding properties improve. This effect requires its addition in one Quantity over 10%, but its exceeding 25%, excessive Additive causes the excretion of an α phase, what is accompanied by a decrease in ductility. The the amount of Cr is in a range above 10% by weight, however not more than 25% by weight, preferably 13 to 20% % By weight.

W is an additional element that is used to obtain an austeniti phase with the high excretion of α-W and one high high temperature strength is essential. Around To achieve effects, W is at least in an amount Add 10 wt .-%, but its excessive addition of more than 30% causes excessive excretion of α-W and a decrease in both oxidation resistance as well also the tight adhesion of an oxide film. Is accordingly the amount of W in the range of 10 to 30% by weight, preferably 12 to 22% by weight.  

Mo is an element of the same group as W, and therefore the replacement of part of W by Mo can be the same Provide function like that of W. However, since its effect is less than that of W, Mo is set in one area of not more than 10% by weight and in a range of W + 2Mo30% by weight.

Fe does not necessarily need to be present in the alloy to be put. However, since in a solid solution state in an austenitic phase mainly containing Ni present Fe can improve the hot deformability and since it is for saving raw materials and reducing Fe is added if the prices are useful. However, its excessive addition softens an austenite phase and reduces the amount excreted γ′-phase, leading to a reduction in high temperature strength leads. Accordingly, Fe is in an amount of 15% by weight or less, preferably 2 to 10 wt .-% added.

Al is an additional element that is used to form a stable γ'-phase after a tempering treatment is essential and in in an amount of at least 0.4% by weight should. Its excessive addition, exceeding 2.5% however causes an increase in the γ′-phase and lowers it Hot formability. Accordingly, Al is in a range of 0.4 to 2.5% by weight, preferably 0.7 to 1.5% by weight.

Part of the Ti is combined with C to form a stable MC-type primary carbide connected and has functions for sub pressing the coarsening of austenitic grains during the Hot deformation and to improve the hot sliding ability. The rest of the Ti is in the γ'-phase in the solid solution state before, whereby the γ'-phase is solidified, and is used for Improvement of high temperature strength. Accordingly, Ti are added in an amount of at least 0.4% by weight,  but its excessive addition exceeding 3.5% by weight Not only lowers hot formability, it also makes the γ′-phase is unstable and causes reductions in Fe Stability after long-term use at high temperatures Accordingly, Ti is in the range from 0.4 to 3.5% by weight, preferably 0.7 to 2.5% by weight.

Furthermore, Al and Ti also have an important function of ver improved oxidation resistance. Form Al and Ti namely oxide films on the inside of those described above granular α-W layer when the surface scale is formed, whereby the close adhesion of the oxide film in interaction with the effect of the granular α-W layer is improved, what to improve a high temperature oxidation resistance and the hot sliding ability.

Like Ti, part of both Nb and Ta combined with C to form stable MC-type primary carbides den, and they have functions of suppressing the ver coarsening of the austenitic grains during hot working tion and to improve a hot sliding ability. Of the The rest of both Nb and Ta is in the γ′-phase in Solid solution state before, causing the γ'-phase solid solution is solidified, and serves to improve the high temperature temperature resistance. Accordingly, Nb and Ta can vary depending Need be added. However, since their excessive addition of more than 3% by weight reduces the hot deformability, are Nb and Ta in a range of 3 wt .-% or we Niger.

Zr and B are used to improve high temperature strength and ductility through their grain boundary strengthening function effective, and at least one of them can be of the alloy be added to the invention in an appropriate amount. Their effect is obtained with a small amount added.  

Zr and B amounts of more than 0.1% and 0.02% by weight, respectively lower the melting point when heated, thereby reducing the Hot formability is deteriorated. Accordingly, they are upper limits of Zr and B 0.2% by weight and 0.02% by weight, respectively.

Mg and Ca not only improve the purity of the alloy as strong deoxidation and desulfurization elements, son also serve to improve ductility when the Alloy is stretched, in creep deformation and / or in Is hot deformation. Accordingly, at least one of them be added in an appropriate amount. Your we kung is obtained with a small additional amount. If the Amounts of Mg and Ca exceed 0.02% by weight, the decrease Melting start points when heated, making the malleable is deteriorated. Accordingly, the upper limit is for both Mg and Ca 0.02%.

Ni forms a stable austenitic phase and becomes one Matrix for both the solid solution and the selection extension of the γ′-phase. Next, since Ni has a solid solution with can form a large amount of W, an austenitic Matrix with high strength at high temperatures obtained, and therefore Ni is the rest of the alloy.

Apart from the elements described above, up to to 10 wt .-% Co of the alloy of the invention who added the.

Co exists in the austenite of the matrix in the solid solution state, thereby having a certain solid solution strengthening function is enough, and also has an effect to improve tight adhesion of the oxide film. Since Co in the Ni matrix in Solid solution state exists and since Co the excretion of the γ′-phase hardly affected, Co is favorable. However, since Co  An expensive item is its addition in large quantities not preferred.

In addition to the elements described above, random Impurity elements in the alloy of the invention in following area:

P0.02%, S0.02%, O0.03%, N0.02%.

The desired range is as follows:

P0.01%, S0.01%, O0.01%, N0.01%.

On the other hand, elements such. B. Y, rare earths and Hf, a reduction in hot workability and are there not necessarily added to the alloy of the invention. However, they have an effect to improve the tight Adhesion and oxidation resistance of the oxide film and can can therefore be added in the following areas:

Y0.2, rare earths 0.2, Hf0.2%.

V is the other of the alloy of the invention because of the Effect added to improve the high temperature strength inferior elements, and Re increases costs the alloy, although it does improve the high temperature door strength contributes. Accordingly, both of the alloy not necessarily added to the invention, but can in be added to the following areas:

V1%, Re1%.

The high heat resistant nickel base alloy described above tion of the invention is considered a block by such Refining step like vacuum alone or after the vacuum  melt performed electroslag remelting or obtained vacuum remelting afterwards, which Block then through such a deformation step as hot forge or hot roll etc. to make primary products will work.

As described above, these materials become practical used after solution annealing treatment at 900 up to 1150 ° C and a tempering treatment at 600 to 850 ° C were subjected to the elimination of the γ′-phase.

Fig. 1 is a photograph of the metal microstructure of a cross-sectional surface portion obtained after repeating an air cooling treatment to room temperature five times after holding at 900 ° C in atmospheric air for 16 hours, which photograph is obtained using a scanning type electron microscope, and Fig. 1 shows also a schematic representation that explains the phases existing in photography.

example 1

Blocks of 15 kg each were made from alloy no. 1 to 28 according to the invention, the comparative alloys No. 41 and 42 and the conventional alloys No. 51 to 54, which are all listed in Table 1 by vacuum-in production melts, and then bars of 30 mm × 30 mm cross section from the blocks by hot forming mung manufactured. Together with the compositions of the Alloys in Table 1 are also the calculated MC type carbide amounts, the double values of the C-quantities in At .-% are the α-W quantities, which are determined by image analysis with respect to the Alloys No. 1 to 28 of the invention, the comparative le  alloys No. 41 and 42 and the conventional alloy No. 51 were measured, and the calculated γ′-amounts that are represented by the following equation for which Le alloys No. 1 to 28 of the invention and the comparative le alloys No. 41 and 42 listed:

Calculated γ ′ = 4 (0.026 [Cr] + 0.13 [Mo] + 0.13 [W] + 0.16 [Al] + 0.68 [Ti] + 0.5 [Nb] + 0.5 [Ta] - [C])

(the elements in square brackets each mean At .-% of the elements).

The amounts of α-W were measured using the samples, to mirror that by polishing the cross sections of the samples like surfaces after a heat treatment shown below and subsequent corrosion was obtained in aqua regia the. There were particles with a size of 5 microns or more observed under an optical microscope, and a surface of 8000 mm² was an image analysis to determine the Subject to area share. Particles with a Size under 5 µm under a scanning type electron microscope was observed and the area was 8000 µm² subjected to analysis to determine the proportion of area. The The amount of α-W was independent of the sum of the two calculated area ratios.

Here the comparative alloy No. 41 a higher amount of carbon in comparison with those of the alloys of the invention, and the comparative alloy No. 42 is of a set tongue in which the calculated γ′-quantity and the Cr-quantity are expressed riger than that of the alloys of the invention. The be known alloy No. 51 is that according to JP-OS 3-61345; the well-known alloy No. 52 is the highly heat-resistant egg sen base alloy A286; the well-known alloy No. 53 is Precipitation hardening hot forming tool steel; and the well-known alloy No. 54 is JIS SKD61.

Alloys were used for these hot-formed materials gen No. 1 to 28 of the invention and the comparative alloy gen No. 41 and 42 a solution heat treatment by oil removal subjected to cooling after holding at 1050 ° C. for 30 minutes and then subjected to a tempering treatment which the Gradual cooling steps after Hal 8 hours at 720 ° C and then air cooling after 8 hours according to holding at 620 ° C. The well-known alloy No. 51 was a solution heat treatment by air cooling after holding for 30 minutes at 950 ° C. The be  known alloy No. 52 became solution heat treatment by air cooling after holding at 980 ° C for 30 minutes and a tempering treatment by air cooling after 16 hours Keep exposed at 730 ° C. The well-known alloy No. 53 was brought on by rapid cooling after holding for 30 minutes Hardened 1000 ° C and then annealed, so that a hardness of 382 HV was obtained. The well-known alloy No. 54 was by air cooling after holding for 30 minutes 1020 ° C hardened and then annealed, so that a hardness was obtained from 446 HV.

The alloys shown in Table 1 were measured hardness at room temperature and 700 ° C, a tensile test at room temperature of 700 ° C and the measurement of thermal expansion coefficient from room temperature to 700 ° C fen. The hardness was measured with a Vickers hardness meter at ei ner load of 98 N measured. The tensile test was under use a sample that is used to obtain an egg diameter of 6.35 mm on a parallel part of the same and a distance of 25.4 mm between the on markers was deformed.

A hot slide test was used to evaluate the hot slide carried out. In this test, a round bar was used Test piece of 5 mm in diameter and 20 mm in length produced and attached to a clamp on a drill. An end face of the specimen was placed on at 600 ° C heated block made of JIS SNCM439 at a Speed of 1540 rpm pressed for 30 s. The press load was increased, and a seizing load was defined by a load at which the specimen on Block got stuck. The higher this he seizes generating load is, as the better the hot sliding speed at high load.  

A hot wear test was carried out to test the hot wear evaluate wear resistance. This test is a be Known test procedure, the wear of a hot smear deform simulates.

This test method is more detailed in JP-OS 5-260556 than Invention of the present inventors described. With this Tests were made on an outer end of a round bar specimen with a diameter of 16 mm both a heat cycle Heating and cooling as well as friction sliding against repeats a pen made of JIS S45C that points to was heated to about 800 ° C, thereby causing one of hot cracks wear on the end face of the specimen to call. The heating temperature of the specimen was set to 600 ° C. The friction sliding against the pin was at a surface pressure of 14 N / mm² and at a Speed of 400 rpm for 5 s, and the cooling treatment took place in water at 32 ° C. for 3.5 s. After how repetition of 2000 cycles with heating, friction sliding and cooling as a cycle, the Ver depth of wear on the end face of the specimen with a Surface roughness meter to determine wear quantity measured. A cross-sectional microstructure was also developed on worn area of the specimen observed to the Number and the maximum length of the heat cracks that occurred measure up.

Furthermore, the oxidation resistance was evaluated Round bar specimens 8 mm in diameter and 15 mm in length made from the alloys shown in Table 1, an oxidation weight change after five re-runs make up for the air cooling treatment to room temperature Hold for 16 hours at 900 ° C in atmospheric air measure up.  

The various test results described above are in listed in Table 2. It was confirmed that Le gations of the invention of higher hardness at 700 ° C and higher tensile strength at 700 ° C than the comparison alloy and the conventional alloys and from recorded mechanical properties in a high temperature door area. Their thermal expansion coefficients showed Values close to those of the well-known alloy no. 54 hot forming tool steel shown. The well-known Le alloy No. 52 had a high coefficient of thermal expansion in comparison with that of the known alloy no. 54 specified hot forming tool steel.

The change in oxidation weight was repeated after five times repeat the step of holding at 900 ° C for 16 hours atmospheric air with the results observed that the other alloys with the exception of the known alloy stanchions No. 53 and 54 showed an increase in values and that the tight adherence of the oxidation films was good.

It has been found that when the Cr content is decreased like in the case of the comparative alloy No. 42 a weight increase tion occurs due to oxidation and that another Reduction of the Cr content as in the case of the comparison alloy No. 51 a significant increase in weight due to Oxidation compared to the alloys of the invention occurs and that therefore a large amount of Cr as in the Le gations of the invention was required to the Oxidati ons resistance to improve. On the other hand, Heiß showed deformation tool steel like the well-known alloys No. 53 and 54 a decrease in the oxidation weight change te. This is because the oxide film is thick was peeled off after an oxidation test and that the Oxidation weight excluding this peeled oxide films, which shows that the close liability of the Oxide films lower than those of the alloys according to the invention gen is.

The schematic representation of the structural phases based on observation is shown in FIG. 10 to explain the invention after an oxidation test observed under a scanning type electron microscope. The phases forming the oxide film were identified with micro X-ray diffraction and energy distribution type X-ray analysis. Each of the alloys of the present invention has a three-layer structure, which has an outer, mainly Cr containing oxidized layer, a granular α-W layer and an inner, mainly containing Al and Ti oxidized layer in order from the surface side when the alloy is one oxidizing atmosphere at a high temperature of 700 to 1000 ° C was exposed. The structure thus has a shape in which the granular α-W layer is inserted between the outer, mainly Cr-containing oxidized layer and the inner, mainly containing Al and Ti oxidized layer, and because of this oxidation film structure, the alloys according to the invention have that high oxidation resistance, the close oxide film adhesion as well as the associated high hot gliding ability and hot wear resistance.

It was confirmed by the hot sliding test that the Alloys according to the invention cause a seizure loads in comparison with those of the known Alloy No. 54 illustrated hot forming tool steel. Excellent tight grip and stabilization act and a high temperature strength in a obtained Oxide films are required with regard to the hot sliding ability, and it was confirmed that the alloys of the present invention met these requirements and the excellent Had hot sliding ability.

The hot wear test showed that he Alloys according to the invention have very low amounts of wear in comparison with that of the known alloy no. 54 of the hot forming tool steel shown. The well-known alloy No. 51, which a large amount of W had an amount of α-W exceeding 30% by volume and a low Cr content. Therefore, although No. 51 a high seizure caused by seizure when hot sliding test, the oxide film obtained was poor tight adhesion and stability after the passage of a long period of time and is therefore related to wear resistance in comparison with the alloy according to the invention inferior. There were hot cracks in all alloys causes, except the well-known alloy No. 53. There the well-known alloy No. 53 a low AC₁ point the temperature on the end face of the Pro exceeds benstücks easily this AC₁ temperature by the Rei exercise sliding, causing a conversion of the end face to Au  stenite is caused, which is an extremely high reduction the strength of the friction sliding part with the result caused hot cracks to rub off easily and after Test was not observed even though the cracks were formed ren.

Since the well-known alloy no. 52 high thermal expansion coefficient, hot cracks easily occurred. Dementia The hot cracks accordingly increase the coefficient of friction of the Friction sliding surface, and the wear became more than that of the alloys according to the invention. The comparative theory tion No. 41 with a high C content formed the chains structure of an MC-type carbide, and hot cracks developed in this part with the formation of many hot cracks that have an on increased wear caused. Since the comparison le alloy No. 42 a 10 at% lower γ′-amount than that of the alloys according to the invention, she demonstrated 700 ° C a lower tensile strength than that of the inventor alloys according to the invention and caused more ver wear. It was confirmed with this test that the inventions alloys according to the invention of excellent resistance against hot wear that causes hot cracks.

Example 2

Alloy No. 4 according to the invention and the known Alloys No. 52 and 53, all of which are in Table 1 heat treatment in the same Way as in Example 1 and then machinability subjected to test using a ball head mill. On Machining center was used to measure the amount of wear the cutting edge of it to measure so the cutting availability thanks to a ceramic-cemented card bid existing ball mill using a washer  to examine the cutting oil. The test was among the Conditions of a cutting speed of 50 m / min, ei nes feed of 0.5 mm / blade, cutting amounts of 2 mm in an axial direction and 1 mm in a circumferential direction and a cutting length of 25 m performed to Ver wear width of a flank of a cutting edge in the end mill to measure. The test results are in Table 3 shown.

Although the alloys according to the invention belong to the category of include heat-resistant nickel-based alloys, show the alloys have excellent machinability Comparison with that of the known hot forming tool steel No. 53 and the highly heat-resistant iron base alloy No. 52. This good machinability arises by the distribution of the fine α-W phase. So he did Alloys according to the invention are sufficiently machinable speed even after an occasional treatment and can therefore be used for use a pre-hardened tool that does not heat Treatment after processing into molds is required.

Table 3

Example 3

The examples in which the alloys according to the invention were used for hot deformation molds, are fol described above.

The materials made similar by melting the components Lich those of alloys No. 1 shown in Table 1 10 and 14 of the invention, and the mate rial of the composition of the be shown in Table 1 known alloy No. 54 were made. Hot forming Forms were created from these materials, and practical tests were carried out. The results of it are shown in Table 4. The shape is used for generation a transmission shaft, which is a motor vehicle part, and de Its dimensions are 80 mm in diameter and 160 mm in diameter Length. The shape for generating this gear shaft has a rough shape for roughly deforming the material and one Finishing form to end the deformation of the rough deformed material, and the test was carried out using Coarse form carried out, the heavily worn has been. A deformed material was S35C and was through a high frequency heater heated to 1200 ° C. A Crank press with a maximum capacity of 1600 t used for forging, and a lubricant of the white Group was applied to the mold surface after each press blow sprayed on.

The well-known alloy No. 54 is JIS SKD61. With a heat The treatment became the shape after rough deformation of the material than heated to 1020 ° C to form the hot deformation mold, and an oil quench was carried out in which the heated mold was immersed in oil of 200 ° C, and there after the tempering was carried out so that the hardness 446  HV will. Then the final deformation was carried out, and the The products obtained were subjected to practical tests.

Table 4

The service life of the hot produced from these alloys Deformation shapes are shown in Table 4. With this The forging parts of the molds are hot forged mix to a high degree by contact with a high temperature workpiece and by sliding with the workpiece influences. The shapes examined were made with lubricants the white series instead of using conventional ones Lubricants of the graphite series lubricated, what special to increase the heat generation effect by sliding led on the workpiece. As a result, the well-known Alloy No. 54 the softening of the annealed martensite and austenite transformation due to thermal on flow and due to the climb of the AC₁ conversion points on what leads to a decrease in the strength of a Partial surface and excessive wear with shortened the service life. The lubricant of the white series was on the mold surface after each press blow sprayed using the molds, and therefore revealed a heat cycle of heating and cooling for the  Mold surface so that hot cracks appear on the surface Because the hot on the mold surface cracks to increase the coefficient of friction with the Guide workpiece, was the ver by sliding on the workpiece caused heat generation more so that the heat influence was increased on the mold surface. In addition, the shear stress caused more on the mold surface, see above that the plastic flow of the mold surface is enhanced was and therefore the wear was accelerated. The be known alloy No. 54 was largely influenced by the Occurrence of hot cracks thermally influenced, and that resulting shear stress exceeded the strength of the shape surface part so that easily causes wear and tear the mold life has been shortened.

Alloys No. 10 and 14 of the invention were suppressed because of their excellent oxide film properties Heat generation caused by sliding on the workpiece. Au was also in the alloys, even if the thermal Influence was caused, the high temperature strength of the surface part higher than that of the forging Forming caused shear stress, so that on the surface No plastic flow took place and the abrasion was minimized, which extended the service life of the mold.

Hot cracks were also found on alloys No. 10 and 14 of the Invention caused. The hot cracks were on the alloy No. 14 more, and their service life was therefore shorter. The Le alloy No. 14 is an alloy with a large amount of α-W. An observation of the microstructure on the worn Part of the form after a practical test led to the festival position that hot cracks developed along the α-W and that the Hot cracks tend to appear at points with a larger amount of α-W occurred, which led to increased wear. In the front lying practical test, there was a close relationship between  the occurrence of hot cracks and wear, and when used for an insufficiently lubricated mold the effect of seizure resistance of the α-W during the Hot gliding on.

The alloys of the invention were known alloys superior in high temperature hardness, but in egg few cases regarding the hardness at room temperatures and submit. In this case, a shape with a large thickness occasionally due to the press load during the smithing Deformation deformed. However, it was made by making one Form in combination of the alloys according to the invention, the were applied to a molded part with the known Le alloy No. 54 or JIS SKT4, which ver for a base part was used, possible to improve the wear to exploit the durability of the alloy according to the invention.

It was clear from the foregoing that the invention Alloys perform excellently as hot forging have in many cases in temperature range be operated from 700 to 900 ° C.

Example 4

An example in which the alloy according to the invention for a Cu alloy extrusion tool was used in described below.

It became a material by melting the stock parts similar to those of the alloy shown in Table 1 tion No. 10 of the invention, and another Material of the composition shown in Table 1 well-known alloy No. 52 manufactured. Hot extrusion Witness was made from these materials, and practical  tests have been carried out. The results of this are shown in Table 5. The be shown in Table 1 Known alloy 52 is JIS SUH660 and under the name of A286 known. This alloy is called a hot extrusion press known for Cu or a Cu alloy.

Table 5

It became a double extrusion hot extrusion tool, obtained by shrinking, where JIS SKT4 was used for the outer cylinder and the Alloy No. 10 of the invention and the known alloy No. 52 for the production of inner cylinders for comparison were used. The small-sized tools of the dop construction in which the outer cylinder has an outer diameter had a diameter of 200 mm and the inner cylinder had an Au outer diameter of 100 mm and an inner diameter of 60 mm, the length of both being 200 mm from alloy no. 10 of the invention and from the known Alloy No. 52 manufactured. These tools were pure copper knot to carry out extrusion tests pel at 950 ° C with a 100 t press. The inside their cylinders were exposed to a high temperature of around 800 ° C and subjected to a high pressure of about 500 N / mm², wherein Turtle-back-like hot cracks caused by a thermal  Stress was caused and the surface wore off peeled, which led to the end of the service life. In the case the well-known alloy No. 52 the appearance of Hot cracks on the inner surface after extrusion of about 10,000 pieces observed. On the other hand, one observed in Alloy No. 10 of the invention after extrusion only a few hot cracks from around 30,000 pieces.

Since the alloy no. 10 of the invention has a high tensile strength speed and a low coefficient of thermal expansion in one Had high temperature range, hot cracks were hardly caused gently, which considerably increases the service life of the extrusion tool extended. This result clearly showed that the Alloys of the invention perform excellently Have hot extrusion tool.

The alloys of the invention are excellent in their High temperature properties, such as B. hot sliding, Hot abrasion resistance, hot crack resistance and oxidation resistance, machinability and hot formability. Your Use for hot or hot forming molds that are used for Formation of automotive parts such. B. crankshafts and Crank rods for motor vehicles, used and for Hot extrusion tools for Cu, Al or their alloys is suitable to compare the tool life to improve significantly with conventional materials.

Claims (9)

1. High heat resistant nickel base alloy with one a structure subjected to tempering treatment, the one MC type carbide phase from 0.02 to 1.5 as in at% amount calculated from 2 [C], the [C] at% Koh lenstoff means a γ′-phase of 10 to 30% as in at% from 4 (0.026 [Cr] + 0.13 [Mo] + 0.13 [W] + 0.61 [Al] + 0.68 [Ti] + 0.5 [Nb] + 0.5 [Ta] - [C]) calc amount, each bracketed element at% of the element means and not added elements are calculated as zero, α-W phase from 0.5 to 30 Vol .-% and the remainder mainly containing Ni austenitic phase. 2. Nickel-based alloy according to claim 1, characterized records that after exposure to high temperatures temperatures of 700-1000 ° C in atmospheric air Surface scale structure that has at least three Layers of an outer oxidized, mainly Cr containing layer, a granular α-W layer and an inner oxidized one, mainly Al and Ti containing layer in that order from the Has surface side from.   3. Nickel-based alloy according to claim 1 or 2, characterized characterized in that they essentially weight from 0.002-0.15% C, up to 2% Si, up to 3 Oo Mn, <10-25% Cr, 10-30% W, up to 15% Fe, 0.4-2.5% Al, 0.4-3.5% Ti and balance Ni and random There is contamination. 4. Nickel-based alloy according to claim 3, characterized characterizes that a part of the Ni by up to 3.0 wt .-% Nb and / or up to 3 wt .-% Ta is replaced. 5. Nickel-based alloy according to claim 3 or 4, characterized characterized in that a part of the Ni by up to 10 Wt .-% Mo in the range of W + 2 Mo 30 wt .-% replaced is. 6. Nickel based alloy according to any one of claims 3 to 5, characterized in that part of the Ni by up to 0.2% by weight of Zr and / or up to 0.02% by weight B is replaced. 7. Nickel based alloy according to any one of claims 3 to 6, characterized in that part of the Ni by up to 0.02% by weight of Mg and / or up to 0.02 % Ca is replaced.   8. Process for making a highly heat-resistant Nickel-based alloy according to one of claims 1 to 7, characterized in that the tempering treatment at a temperature in the range of 600-850 ° C leads. 9. The method according to claim 8, characterized in that the tempering treatment once or twice during a Total duration of at least 3 hours becomes.