Cobalt Chromium Alloy Powder

Abstract

A cobalt-chromium alloy without titanium for powder, consisting of (in mass %): C 0.40 - 1.50%; Cr 24.0 - 32.0%; W 3.0 - 8.0%; Mo 0.1 - 5.0%, where 4.0 < W + Mo < 9.5 is satisfied with respect to the content rates of W and Mo in mass %; Nb at most 0.5%; Ta at most 0.5%, where Nb + Ta < 0.8 is satisfied with respect to the content rates of Nb and Ta in mass %; Ni 0.005 - 25.0%; Fe 0.005 - 15.0%, where Ni + Fe > 3.0 is satisfied with respect to the content rates of Ni and Fe in mass %; Mn 0.005 - 5.0%; Al at most 0.5%; N 0.0005 - 0.15%; Si < 0.3%; Cu at most 0.4%; O 0.0001 - 0.1%; P at most 0.015%; B at most 0.015%; S at most 0.015%; Co the balance, and impurities resulting from production; in particular, Zr at most 0.03%; Ti at most 0.025%.

Description

[Technical field]

[0001] The present invention relates to chemical compositions for cobalt chromium alloy powders. [Background technology]

[0002] An important feature of cobalt-chromium alloys is their high wear resistance, which is ensured by certain alloying elements, in particular carbides. The alloys do not usually have other strengthening phases, for example the coherent FCC(Co,Ni)3Ti, which is similar to the γ' phase in nickel-based alloys. Typical carbides in Co-based wear-resistant materials are MC, M6C, M7C3 and M 23 C6 precipitates. By "M" the following elements are understood: MC ((Ta, Ti, Zr, Nb, W, Cr)C), M6C ((Cr, Mo, W, Co)6C), M7C3 ((Cr, Mo, W, Co)7C6) and M 23 C6 (Cr, Mo, W, Co) 23 C6), which are considered here as essential but not exclusive. Due to their high abrasiveness, these materials are difficult to process. Hot isostatic pressing (HIP) as a method in the production of large components is therefore gaining in importance as well as spraying during welding build-up and / or surface treatment.

[0003] Stellite (trademark of Kennametal) is included in the "family tree" Celsite (trademark of DEW) (cobalt-based alloys) of the material diagram of the Deutsche Edelstahlwerke of October 2013. One of the most widespread types of Stellite is Stellite No. 6 (UNS R30006) consisting of (in mass%) 1.1% C, 28.0% Cr, 4.5% W, 1.0% Ni, 1.0% Fe, balance Co, which, based on the C content, was also assigned to the category of "crack-free welding behavior". This alloy has, among other things, a good combination between corrosion resistance, wear resistance and hardness. However, Stellite No. 6 exhibits a relatively small elongation at break of about 1%.

[0004] In the case of generative manufacturing, not only the chemical composition of the alloy but also phase transformations play a major role, since during processing there is a risk of crack formation due to segregation effects and due to additional stresses due to the dissolution of phases. Furthermore, cobalt-chromium alloys, from a certain C content, have eutectic reactions during the solidification process, which bring additional stresses into the material and lead to the formation of cracks if the material itself has a relatively low ductility. This generally makes welding of wear-resistant cobalt-chromium alloys difficult.

[0005] Highly segregating elements such as B, Zr and Si reduce the weldability of nickel and nickel-cobalt alloys. B, Zr and Si segregate highly during solidification and significantly increase the tendency to form thermal cracks. Furthermore, the workability during synthetic manufacturing processes is deteriorated by the elements S, O, N, P and Pb.

[0006] JP 61243143 A discloses a superplastic cobalt alloy having a defined grain size of 10 μm or less and consisting of (in mass%) 0.15-1.0% C, 15.0-40.0% Cr, 3.0-15.0% W or Mo, less than 1.0% B, 0-20% Ni, 0-1.0% Nb, 0-1.0% Zr, 0-1.0% Ta, 0-3.0% Ti, 0-3.0% Al, and the balance Co.

[0007] US2017 / 0241287 A1 discloses a powder metallurgy cobalt alloy consisting of (in mass%) 0.05-0.8% C, 25.0-32.0% Cr, 4.0-10.0% W, 5-15% Ni, 0.5-2.0% Fe, 0.3-1.5% Si, balance Co. Further, a series of elements Ti, V, Y, Zr, Nb, Hf and Ta is defined, which are described as follows: one element is referred to as a first element having a mass% of 0.01-0.5%, in addition to which another is referred to as a second element, which is in a higher numbered group in the periodic table or has a higher period number in the same group, and is present at a mass% of 0.01-0.5%.

[0008] US 2016 / 0258298 A1 discloses a method for manufacturing near net shape metal components with examples from various nickel-based and cobalt alloys, such as FSX414 and Mar-M-509.

[0009] EP3453775 A1 discloses a cobalt alloy consisting of (in mass%) 0.08-0.25% C, less than 0.1% B, 10.0-30.0% Cr, 5.0-12.0% W and / or Mo, up to 30% Ni and Fe in total, with Fe being less than 5.0%, 0.5-2.0% Ti, Zr, Nb and Ta in total, up to 0.5%, Si, up to 0.5%, Mn, 0.003-0.04% N, balance Co, and a component manufactured from said alloy using a synthetic manufacturing process.

[0010] EP3278907 A1 discloses a metal powder based on at least 50% by weight of Ni, Fe and Co. At least one of the following elements is present in the powder: C, Si, Cr, Mo, Al, Ti, V, W, Nb, Zn, Ta, B, Ag, Cu and Sn and other process-induced impurities, in which the particles have a spherical morphology with a 10% particle size D10 of 10 μm or more and a volume Y of 7.5 to 24.0, calculated according to the following formula: Y=D50×ρ×S, where D50 is the particle size of 50% by volume of the powder, ρ is the actual density of the powder and S is the specific surface area of ​​the powder. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 61-243143 [Patent Document 2] US Patent Application Publication No. 2017 / 0241287 [Patent Document 3] US Patent Application Publication No. 2016 / 0258298 [Patent Document 4] European Patent Application Publication No. 3453775 [Patent Document 5] European Patent Application Publication No. 3278907 [Non-patent literature]

[0012] [Non-Patent Document 1] "Descent tree" of materials diagrams from the Deutsche Edelstahlwerke Celsite, October 2013 Summary of the Invention [Problem to be solved by the invention]

[0013] The object of the present invention is to provide a titanium-free cobalt-chromium alloy which allows for the productive manufacture of nearly crack-free component structures with good processability. At the same time, components made from the alloy according to the invention should combine increased elongation at break with higher hardness and thus increased wear, oxidation and corrosion resistance at moderate service temperatures.

[0014] The object of the present invention is also to provide a method for producing a titanium-free cobalt-chromium alloy, which allows a high quality powder to be achieved.

[0015] A further challenge is to make the alloys usable for specific applications. [Means for solving the problem]

[0016] The object of the present invention is to provide a titanium-free cobalt-chromium alloy for powders, which comprises (in mass %) C 0.40~1.50% Cr 24.0~32.0% W 3.0~8.0% Mo 0.1 to 5.0%, where the content ratio of W and Mo in mass% satisfies 4.0≦W+Mo≦9.5; Nb max. 0.5% Ta max 0.5%, where the Nb and Ta contents in mass% are Nb+Ta≦0.8; Ni 0.005~25.0% Fe 0.005-15.0%, where the content ratio of Ni and Fe in mass% satisfies Ni+Fe>3.0; Mn 0.005~5.0% Al max. 0.5% N 0.0005~0.15% Si < 0.3% Cu max. 0.4% O 0.0001~0.1% P max 0.015% B Maximum 0.015% S max 0.015% Co residues and impurities resulting from production, especially Zr max 0.03% Ti max 0.025% This is achieved by the titanium-free cobalt-chromium alloy for powders consisting of

[0017] Further advantageous aspects of the alloy according to the invention are set out in the associated dependent claims.

[0018] The above-mentioned further object is also achieved by a method for producing a powder from this alloy, which comprises melting the alloy in a vacuum induction melting furnace and atomizing it in a closed atomization device, in which the molten metal is fed through a nozzle into a feed gas stream having a specific gas flow rate, and the solidified powder particles are collected in a hermetically sealed container.

[0019] Advantageously, the following relationship: 10.0% by volume or less M 23 C6≦40.0% by volume, and M7C3≦10.0% by volume should be met especially after heat treatment.

[0020] The alloy according to the invention can preferably be used as a powder for generative manufacturing processes and / or in combination with HIP processes, for HIP processes and for welding overlays and / or coatings.

[0021] Preferred aspects of said uses are set out in the associated dependent claims.

[0022] In what follows, all concentration statements are given in weight percent unless expressly noted otherwise.

[0023] The carbon content is between 0.40 and 1.50%, where the preferably defined content is: 0.40~1.40% 0.42~0.95% >0.65~1.50% can be adjusted within a range of

[0024] This also applies to the element chromium, which is adjusted to a content of 24.0-32.0%. The preferred content can be indicated as follows: 25.0~31.0% >25.0~31.0% 26.0~31.0%.

[0025] This also applies to the element molybdenum, which is adjusted to a content of 0.1 to 5.0%. The preferred contents can be indicated as follows: 0.1-4.0% 0.1~<4.0% 0.1-3.0%.

[0026] Furthermore, it is advantageous to add tungsten to said alloy in a content of 3.0-8.0%, where the following must be satisfied for the contents of W and Mo in mass %: 4.0≦W+Mo≦9.5. The preferred ranges are: 4.2≦W+Mo≦9.0% is obtained.

[0027] The Zr content is adjusted to a maximum of 0.03% (impurity). Maximum 0.025% Maximum 0.020% is limited to.

[0028] The Hf content is also limited to a maximum of 0.015%. Maximum 0.010% Maximum 0.008% is limited to.

[0029] Furthermore, titanium is limited to a maximum content of 0.025% (impurity), where the contents of Zr, Hf and Ti in mass % must satisfy Zr+Hf+Ti≦0.04. The preferred ranges are: Zr+Hf+Ti≦0.035% Zr+Hf+Ti≦0.030% is obtained.

[0030] The Nb content is limited to a maximum of 0.5%. Maximum 0.4% Maximum 0.3% is limited to.

[0031] Furthermore, Ta is limited to a maximum content of 0.5%, where the Nb+Ta≦0.8 must be satisfied for the Nb and Ta contents in mass %. The preferred range is: Nb+Ta≦0.6% Nb+Ta≦0.5% is obtained.

[0032] This also applies to the nickel element, which is adjusted to a content of 0.005 to 25.0%. The preferred content can be shown as follows: 0.005~24.0% 0.005~21.0% 0.005~15.0% >2.0~14.0% >3.0~21.0% >5.0~21.0%.

[0033] This also applies to the element iron, which is adjusted to a content of 0.005 to 15.0%. The preferred contents can be indicated as follows: 0.05~15.0% 0.05~10.0% 0.05~8.0% >2.0~10.0% >3.0~10.0%.

[0034] The Mn content is 0.005 to 5.0%, and the content preferably defined here is 0.005~4.5% 0.005~4.0% >2.0~5.0% can be adjusted within a range of

[0035] The Al content is also limited to a maximum of 0.5%. Maximum 0.35% Maximum 0.25% is limited to.

[0036] The N content is 0.0005 to 0.15%, and the content preferably defined here is 0.001~0.12% 0.001~0.10% can be adjusted within a range of

[0037] The Si content is limited to <0.3%. Preferably, Maximum 0.25% Maximum 0.20% is limited to.

[0038] The element Cu is limited to a maximum of 0.4% in the alloy. Preferably, Maximum 0.3% is limited to.

[0039] The oxygen content is between 0.0001 and 0.1%. The following limitations on the oxygen content are considered: 0.001~0.1% 0.002~0.08% 0.002~0.06% 0.002~0.05%.

[0040] The B content is limited to a maximum of 0.015%. Maximum 0.012% is limited to.

[0041] The sulfur content is also limited to a maximum of 0.015%. Maximum 0.010% is limited to.

[0042] Finally, for further impurities, the following elements that cannot be excluded may be indicated as follows: Pb max. 0.005% Zn max. 0.005% Sn max 0.005% Bi max 0.005% V max 0.005% Y max 0.005% La maximum 0.005%.

[0043] The following relationship: 10.0% by volume ≦ M 23 C6≦40.0% by volume and M7C3≦10.0% by volume must be satisfied, especially after heat treatment. The preferred ranges are 13.0% by volume≦M 23 This is obtained for C6≦38.0 vol.% and M7C3≦8.0 vol.%.

[0044] A method for producing powder from a cobalt-chromium alloy according to the present invention is illustrated below, in which the alloy is melted in a vacuum induction melting furnace, a closed atomizing device is conditioned with a feed gas, the molten metal is fed through a nozzle into a feed gas stream with a specific gas flow rate, and the solidified powder particles are collected in a hermetically sealed container.

[0045] The powder according to the invention is preferably produced in a vacuum inert gas atomization system (VIGA). In this system, the alloy is melted in a VIM furnace and the liquid melt is held for 20 minutes to 2 hours for homogenization. The melt is led to an injection funnel, which is connected to a gas nozzle, where the molten metal is atomized into metal particles using an inert gas under high pressure of 5 to 100 bar. The melt is heated in a melting crucible at 5 to 400°C above the melting point. The metal flow rate during atomization is 0.5 to 80 kg / min and the gas flow rate is 2 to 150 m. 3 / min. Rapid cooling solidifies the metal particles into spheres (spherical grains). The inert gas used during spraying can contain 0.01-100% nitrogen, if necessary. The gas phase is then separated from the powder in a cyclone, which is then packaged. The particles are then classified into a diameter range of 5 μm to 250 μm, gas inclusions with a pore area (pores <1 μm) of 0.0-4% of the total area of ​​the evaluated object, and a density of 2 to about 8.5 g / cm. 3 The alloy has a bulk density of up to the alloy density of 1000 g / mol / g and is hermetically packed under a protective gas atmosphere with argon.

[0046] The particle size spread of the powder is in the range of 5-250 μm, with preferred ranges being 5-150 μm, or 10-150 μm. Said preferred ranges can be achieved by separating out too fine and too large particles by sieving or screening steps. These steps are carried out under protective gas and can be carried out one or more times.

[0047] The inert gas during powder production may alternatively be argon or a mixture of argon with 0.01 to less than 100% nitrogen. The nitrogen content may be subject to the following limitations: 0.01~80% 0.01~50% 0.01~30% 0.01~20% 0.01~10% 0.01~10% 0.1-5% 0.5~10% 1-5% 2~3%.

[0048] Alternatively, the inert gas may optionally be helium.

[0049] The inert gas should preferably have a purity of at least 99.996% by volume, in particular a nitrogen content of 0.0-10 ppmv, an oxygen content of 0.0-4 ppmv, and an H2O content ≦ 5 ppmv.

[0050] In particular, the inert gas may preferably have a purity of at least 99.999% by volume. In particular, it should have a nitrogen content of 0.0-5 ppmv, an oxygen content of 0.0-2 ppmv, and an H2O content ≦ 3 ppmv. The dew point in the apparatus is in the range of -10 to -120°C. It is preferably in the range of -30 to -100°C.

[0051] The pressure during spraying of the powder may preferably be 10 to 80 bar.

[0052] Components and parts, or layers on components and parts, manufactured using additive manufacturing are built up from layer thicknesses of 5-500 μm and immediately after manufacturing have an organized structure with grains of average grain size 2 μm-1000 μm extending in the direction of the structure. A preferred range is 5 μm-500 μm. The manufacture of the components can be carried out, if necessary, by heating the building space and / or by in-situ heat treatment by laser control.

[0053] Furthermore, the above-mentioned powders can be used for the manufacture of components using HIP or conventional sintering and extrusion methods, if necessary. Furthermore, a combination of additive manufacturing and subsequent HIP processes is possible, whereby the post-processing steps described below for generative manufacturing can be used for HIP components.

[0054] The alloy according to the invention can also be used for overlay welding on any kind of metal parts as required, whereby high wear resistance, hardness are achieved together with very good corrosion and oxidation resistance, crack-free or nearly crack-free structure and improved ductility compared to Stellite No. 6.

[0055] Furthermore, the alloy according to the invention may be suitable for the binder jetting method, where the component is built up in layers, but in contrast to the laser melting method, an organic binder is applied locally, which ensures the bonding of the powder particles. After hardening of the binder, the so-called green part is cleaned of the unbound powder and subsequently debound and sintered.

[0056] For the alloys according to the invention, methods and additional devices for pre-heating and post-heating may be advantageous. As an example, the EBM method - electron beam melting can be considered. A powder bed is selectively melted in layers by an electron beam. The process is carried out under high vacuum. The process is therefore particularly suitable for hard substances with low ductility and / or for reactive materials. Pre-heating and post-heating devices can also be integrated into the laser-based method. Parts and components manufactured using additive manufacturing and the other above-mentioned methods, or layers on the parts and components, can be selectively subjected to homogenization annealing, stress relief annealing, solution annealing, and / or precipitation hardening annealing. The heat treatment can be optionally carried out under vacuum or protective gas, for example argon or hydrogen, followed by cooling in a furnace, optionally under protective gas, in air, in a moving annealing atmosphere, or in a water bath.

[0057] The component may be homogenized or stress relieved, if desired, by annealing in vacuum, air or protective gas at a temperature between 400°C and 1250°C for 1 hour to 300 hours, after which the component may be solution annealed, stress relief annealed or precipitation hardened annealed in vacuum, air or protective gas at a temperature between 400°C and 1050°C for 0.5 hour to 30 hours, if desired.

[0058] Thereafter, the surface can optionally be cleaned or processed by pickling, blasting, grinding, turning, stripping, milling, etc. Such processing can optionally be performed partially or entirely even before annealing.

[0059] Components and parts, or layers on components and parts, manufactured using additive manufacturing and other above mentioned methods have an average grain size after annealing of 2 μm to 2000 μm, with a preferred range being 20 μm to 500 μm.

[0060] The term "additive / generative manufacturing" can be further subdivided into rapid prototyping, rapid tooling, rapid manufacturing, etc., depending on the level of application.

[0061] In general, a distinction is made here between: 3D printing with powder, selective laser sintering, Selective laser melting, Electron Beam Melting Binder Jetting Laser cladding welding High speed laser cladding Ultra-high speed laser cladding welding selective electron beam melting, etc.

[0062] The abbreviations used herein are defined as follows: VIM vacuum induction melting VIGA Vacuum Inert Gas Atomization Equipment (Vacuum Induction Melting and Inert Gas Atomization).

[0063] The cobalt-chromium alloy according to the invention should preferably be used in areas where tribological, corrosive and / or oxidative conditions prevail, such as diverters, valves, especially valve seats, brake disks, especially brake wear surfaces, rollers, rods and / or replacement parts for galvanic hard chromium coatings, in the oil, gas and automotive industries, as well as in turbine construction. Furthermore, it is also suitable for the chemical process and packaging industries.

[0064] The limit values ​​claimed for the alloys are therefore individually justified as follows: wear resistance and hardness increase with increasing proportion of carbides. Carbon is mainly responsible for the formation of carbides.

[0065] In order to obtain sufficiently good wear resistance and high hardness, a minimum C content of 0.40% is necessary. If the C content is too high, workability and weldability deteriorate. Therefore, the upper limit is set at 1.50%.

[0066] For good oxidation and corrosion resistance, as well as for carbide formation, it is necessary to have a sufficient amount of Cr in the alloy, at least 24.0%. Higher Cr contents can lead to the formation of undesirable phases, which in turn can reduce the workability of the alloy. Therefore, the upper limit is set at 32.0%.

[0067] The volume fraction of carbides increases with increasing W content. Furthermore, the strength of the alloy increases due to solid solution hardening. To achieve a sufficient percentage of carbides, a minimum content of 3.0% is required. Higher W contents increase the formation of M7C3 carbides, which increases the tendency of the alloy to form cracks during the respective welding process. Furthermore, higher contents significantly increase the cost. Therefore, an upper limit is set at 8.0% W.

[0068] If the W content is high enough, then the Mo content of at least 0.1% will be sufficient to meet the desired M content. 23Further improves the stability of C6 carbide. If the Mo content is too high, workability deteriorates. Therefore, the upper limit is set at 5.0%.

[0069] For good wear resistance due to a sufficiently high volume fraction of carbides, the sum of W+Mo must be greater than 4.0%. If the sum of W+Mo is greater than 9.5%, the cost of the alloy increases significantly.

[0070] The low tendency to crack formation during the compaction process is achieved not only by the balanced concentrations of C, Cr, Mo and W, but also by the reduced formation of metastable M7C3 carbides, which dissolve under the influence of temperature, as well as coarse MC carbides, which are brittle and act as crack initiation sites due to the lack of slip planes. Furthermore, to ensure the workability of the components, it is important to keep the volume fraction of M6C, sigma and Laves phases as low as possible. Thus, CoCr6 in its basic composition (see Tables 1 and 2) has about 15% by volume of M7C6 carbides, which precipitate primarily and become M7C6 carbides from about 1100 °C. 23 The dissolution of block-shaped carbides in M7C3 and the transition to M 23 The precipitation of C6 carbides is complete at about 980° C. This phase transformation leads to further stresses in the material due to volume changes and subsequent crack formation. Therefore, in the alloy according to the invention, the contents of the following elements, which promote the formation of the above mentioned phases, are intentionally severely limited:

[0071] Furthermore, Zr (an impurity) segregates very strongly during the solidification process, increasing the tendency to crack formation. Therefore, the Zr content is limited to a maximum of 0.03%. The Hf content is limited to a maximum of 0.015% and Ti (an impurity) to a maximum of 0.025%. The sum of Zr, Hf and Ti is limited to a maximum of 0.04%.

[0072] Like Zr, Hf and Ti, Nb and Ta particularly stabilize MC carbides, and therefore the contents of Nb and Ta are each limited to 0.5% or less, with the sum of Nb and Ta limited to 0.8% or less.

[0073] A sufficiently high nickel content increases the ductility of the alloy. In addition, it stabilizes the FCC structure. If the content is too high, the strength of the alloy decreases due to a significant increase in stacking fault energy. Therefore, the Ni content is limited to 25.0%.

[0074] The Fe content is limited to a maximum of 15.0%, because at higher contents, it reduces the strength in Co-based alloys. In general, Fe acts similarly to Ni. However, at higher contents, the reduction in strength and increase in ductility can lead to the formation of undesirable phases in the alloy, such as Laves and Sigma. Too low an Fe content causes an increase in the manufacturing cost of the material. Therefore, the iron content should be greater than 0.005%.

[0075] Manganese is limited to 5.0%, because at higher contents this element may increase the tendency to crack formation during the welding process. If the Mn content is too low, the desulfurization action in the alloy cannot be ensured. Therefore, the manganese content should be greater than 0.005%.

[0076] Even very small amounts of aluminum effectively bind oxygen in the molten metal. If the content is too high, the reactivity of aluminum can again adversely affect the weldability. Therefore, the Al content is limited to 0.5%.

[0077] Nitrogen is limited to 0.15% to limit crack formation during compression process, thereby reducing the formation of nitrides. Too low N content will cause the alloy to be more expensive to manufacture. Therefore, the nitrogen content should be greater than 0.0005%.

[0078] Silicon is limited to less than 0.3% because this element, due to its segregation behavior, significantly increases the tendency to crack formation during the compression process. The limitation of the Si content makes it possible to increase the C content.

[0079] Copper is limited to 0.4% because this element reduces oxidation resistance.

[0080] The oxygen content should be less than 0.1%, since this element impairs the mechanical properties of the consolidated parts and / or coatings of the alloy according to the invention. Too low an O content leads to an increase in the production costs of the powder. The oxygen content should therefore be greater than 0.0001%.

[0081] The P content should be kept as low as possible, since this interface active element very significantly increases the tendency to crack formation due to the formation of low melting eutectic during the welding process, and is therefore set at a maximum of 0.015%.

[0082] The boron content should be kept as low as possible, since this interface element very significantly increases the tendency to crack formation during the welding process, and is therefore set at a maximum of 0.015%.

[0083] The sulfur content should be kept as low as possible, since this interface active element forms low-melting eutectic crystals during the respective welding process and significantly promotes the tendency to thermal crack formation. Therefore, a maximum of 0.015% S is set.

[0084] Pb is limited to a maximum of 0.005% because this element reduces workability. The same applies to Zn, Sn, Bi, V, Y and La.

[0085] M 23 The volume of C6 carbides is limited to a maximum of 40% by volume because at higher volumes the ductility of the material becomes very low. 23 If the volume fraction of C6 carbides is too small, the wear resistance of the material decreases. Therefore, a minimum of 10 volume percent of M 23 C6 is required.

[0086] At the same time, the volume of M7C3 carbides is limited to a maximum of 10% by volume, since the proportion of higher phases strongly promotes the tendency to crack formation. [Brief description of the drawings]

[0087] [Figure 1] FIG. 1 illustrates a part manufactured using laser-based additive manufacturing. EXAMPLES

[0088] Extensive test matrices with varying chemical composition were calculated using thermodynamic simulations (JMatPro and ThermoCalc) using the database TTNi8. Exemplary alloys are shown in Tables 1 and 2. The relationship between chemical composition and phase formation can then be explained. For this calculation, a thermodynamic simulation was used without possible diffusion events during solidification, so that the following accompanying elements, which may be introduced from the raw materials or from large-scale production, were not taken into account in the calculation: Cu, P, S, Pb, Zn, Sn, Bi, V, Y, La. The upper limits were set based on a combination of technical experience and economical aspects. In the tables, the alloys CoCr6 and MP75 are shown as typical compositions. The alloy CoCr6 was then taken as the basis for the development according to the invention. CoCr6 in the basic version exhibits multiple carbide formers.

[0089] The objective of the present invention is to develop a 10.0% to 40.0% M 23 The composition was adapted based on the various C contents so that C6 carbides were formed to ensure high hardness and wear resistance, and the formation of M7C3 carbides was limited to a maximum of 10.0 vol.%. The formation of MC and M6C carbides should be reduced or suppressed as much as possible (2 vol.% each) based on their undesirable morphology. Furthermore, the alloy should be as free of Laves and sigma phases as possible. This is achieved by adapting the combination of C, W, Mo, Nb, Ta, Zr, Hf and Ti.

[0090] As in alloys B-42, B-43 and B-44, low contents of Nb and Ta already stabilize the MC carbides. Relatively low contents of the elements Zr, Hf and Ti achieve a similar effect (alloys B-45, B-46 and B-49). The further alloys in the table show examples within the claimed composition range. The alloys can have a large volume of M7C3 carbides without having a large volume of metastable M7C3 carbides in the structure. 23 To achieve C6 carbides, a matched combination of C, W and Mo is essential (Alloys B-2, B-3, B-5, B-7, B-8, B-11, B-12, B-13, B-14, B-15, B-53, B-55, B-65, B-72). With increasing C content (B-70, B-71, B-72), the Cr and W and Mo contents should also increase. This is because even with 1.5% C by weight (B-72), the M 23 It is possible to achieve only C6 carbides (see Table 2).

[0091] Table 1: Chemical composition of exemplary alloys (E: according to the invention, N: not according to the invention, T: prior art), all in mass %: [Table 1-1]

[0092] [Table 1-2]

[0093] [Table 1-3]

[0094] Table 2: Phase stability ranges [Table 2]

[0095] A first exemplary sprayed chemistry (similar to B-12 and B-13 with different Ni content) is shown in Table 3. Using laser-based additive manufacturing, it is possible to produce parts without microcracks at various process parameters (see FIG. 1).

[0096] FIG. 1 shows a material body constructed using laser-based additive manufacturing with different process parameters (exposure methods) that does not have microcracks.

[0097] As predicted by thermodynamic calculations, no primary M7C3 carbides or eutectic solidification were detected. 23 The precipitation of C6 carbides was induced. The advantage of this is that the size and distribution of the carbides can be controlled by heat treatment.

[0098] Table 3: First exemplary sprayed chemical composition. Na Not analyzed.

[0099] [Table 3]

Claims

1. A titanium-free cobalt-chromium alloy for powder applications, comprising (in mass%): C 0.42-0.95% Cr 24.0~32.0% W 3.0-8.0% Mo 0.1 to 5.0%, where the W and Mo contents in mass% satisfy 4.0≦W+Mo≦9.5; Nb max. 0.5% Ta max 0.5%, where Nb+Ta≦0.8 is satisfied for the Nb and Ta contents in mass%; Ni 0.005-25.0% Fe 0.005-15.0%, where the Ni and Fe contents in mass% satisfy Ni+Fe>3.0; Mn 0.005-5.0% Al max. 0.5% N 0.0005~0.15% Si<0.3% Cu maximum 0.4% O 0.0001~0.1% P maximum 0.015% B Maximum 0.015% S maximum 0.015% Co balance, and impurities resulting from production, Zr maximum 0.03% Ti maximum 0.025% Hf max 0.015%, where the Zr, Hf and Ti contents in mass% satisfy Zr+Hf+Ti≦0.04%; The alloy comprising:

2. 2. The alloy of claim 1 having a Cr content (wt%) of 25.0 to 31.0%.

3. The alloy according to claim 1 or 2, having a Mo content (wt%) of 0.1 to 4.0%.

4. The alloy of claim 3 having a Mo content (wt%) of 0.1 to 3.0%.

5. The alloy according to any one of claims 1 to 4, having a W content (wt%) of 0.5 to 6.5%.

6. 6. The alloy according to any one of claims 1 to 5, having a W-content (wt%) of 3.5 to 8.0%, wherein for the contents of W and Mo in wt%, 4.2≦W+Mo≦9.5 must be satisfied.

7. 7. The alloy according to claim 6, wherein the W and Mo contents in mass % satisfy: 4.5≦W+Mo≦9.0%.

8. 8. The alloy according to claim 1, having a Ta content (wt.%) max 0.5%, wherein for the contents of Nb and Ta in wt.%, Nb+Ta≦0.6 must be satisfied.

9. 9. The alloy of claim 8, wherein the range Nb+Ta≦0.5% is satisfied.

10. The alloy according to any one of claims 1 to 9, having a Ni-content (wt%) of 0.005 to 24.0%.

11. The alloy of claim 10 having a Ni-content (wt%) of 0.005 to 21.0%.

12. The alloy according to any one of the preceding claims, having an Fe-content (wt%) of 0.05 to 15.0%.

13. 13. The alloy according to any one of the preceding claims, having a Mn content (wt%) of 0.005 to 4.5%.

14. The alloy according to any one of claims 1 to 13, having a N content (wt%) of 0.001 to 0.

12.

15. The alloy of claim 14 having a N-content (wt%) of 0.001 to 0.10%.

16. 16. The alloy according to any one of the preceding claims, having a Si-content (wt%) max 0.25%.

17. 17. The alloy of claim 16 having a Si-content (wt%) max 0.20%.

18. The alloy according to any one of the preceding claims, having an O content (wt%) of 0.001 to 0.1%.

19. The alloy of claim 18 having an O content (wt%) of 0.002 to 0.08%.

20. 20. The alloy according to any one of claims 1 to 19, having a Cu-content (wt%) max 0.3%, a B-content (wt%) max 0.012%, a S-content (wt%) max 0.010%, a Pb-content (wt%) max 0.005%, a Zn-content (wt%) max 0.005%, a Sn-content (wt%) max 0.005%, a Bi-content (wt%) max 0.005%, a V-content (wt%) max 0.005%, a Y-content (wt%) max 0.005%, a Hf-content (wt%) max 0.015% and a La-content (wt%) max 0.005%.

21. 21. A method for producing a powder from the alloy according to any one of claims 1 to 20, wherein the alloy is melted in a vacuum induction melting furnace and atomized in a closed atomization device, where the molten metal is fed through a nozzle into a feed gas stream having a specific gas flow rate, and the solidified powder particles are collected in a hermetically sealed container.

22. 21. Use of the powder produced from the alloy according to any one of claims 1 to 20 as powder for generative manufacturing processes and / or in combination with HIP processes, for HIP processes, and for welding overlay and / or coating.

23. 21. Use of an alloy according to any one of claims 1 to 20 as a component and / or coating under tribological, corrosive and oxidative conditions or a combination of these conditions.

24. 22. Use of the method according to claim 21 for producing powders for generative manufacturing processes and / or in combination with HIP processes, for HIP processes and for welding overlay and / or coating.

25. 22. Use of the method according to claim 21 for producing components and / or coatings under tribological, corrosive and oxidative conditions or a combination of these conditions.

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