Metal powder for additive manufacturing

Abstract

The present invention relates to a metal powder for additive manufacturing, the composition of which comprises the following elements, expressed in contents by weight: 15% < = Mn < = 35%, 6% < = Al < = 15%, 0.5% < = C < = 1.8%, 0.4% < = Ti < = 4.5%, 0 < = Si < = 3.5%, P < = 0.013%, S < = 0.015%, N < = 0.100%, and the balance being Fe and unavoidable impurities. And optionally comprising Ni < = 8.5% by weight and / or Cr < = 2.5% by weight and / or B < = 0.1% by weight and / or one or more elements selected from the group consisting of Ta, Zr, Nb, V, Ti, Mo and W in a cumulant amount of up to 2.0% by weight, the balance being iron and unavoidable impurities resulting from processing. The invention also relates to a method for producing such a powder and to a method for producing a printed part therefrom.

Description

Technical Field

[0001] The present invention relates to a metal powder for the manufacture of steel parts, and in particular for the additive manufacturing of steel parts. The invention also relates to a method for manufacturing a metal powder. The powder according to the invention is particularly well suited for the manufacture of safety parts or structural parts with low density for vehicles, such as land motor vehicles. It can also be used in particular for the manufacture of parts for defense, naval, or armor applications. Background Art

[0002] Environmental restrictions force car manufacturers to continuously reduce the CO2 emissions of their vehicles. To this end, car manufacturers are looking for various ways to reduce the weight of motor vehicles.

[0003] This can be achieved in particular by reducing the density of the steel used to manufacture the component by alloying it with other metals that are lighter than iron.

[0004] Steels containing high levels of manganese, aluminum and carbon, often referred to as triplex steels, can show density levels below 7.4 g / cm3. Their solidified structures are shown to contain kappa carbides (Fe, Mn) 3 Austenitic matrix of AlCx and ferrite.

[0005] However, due to their high aluminum and carbon content, they are difficult to manufacture by conventional casting methods. Recently it has been proposed to manufacture them by additive manufacturing, but the mechanical properties of the parts obtained by such methods are not high enough. Summary of the invention

[0006] The object of the present invention is therefore to remedy the drawbacks of the prior art by providing a new method for obtaining components having low density without manufacturability problems and having good mechanical properties.

[0007] To this end, a first object of the present invention comprises a metal powder for additive manufacturing, the composition of which, expressed in terms of content by weight, comprises the following elements:

[0008] 15%≤Mn≤35%

[0009] 6%≤Al≤15%

[0010] 0.5% ≤ C ≤ 1.8%

[0011] 0.4%≤Ti≤4.5%

[0012] 0≤Si≤3.5%

[0013] P≤0.013%

[0014] S≤0.015%

[0015] N≤0.100%

[0016] and optionally contains Ni≤8.5 wt.% and / or Cr≤2.5 wt.% and / or B≤0.1 wt.% and / or one or more elements selected from Ta, Zr, Nb, V, Mo and W in a cumulative amount of up to 2.0 wt.%, the balance being iron and unavoidable impurities resulting from processing.

[0017] The metal powder according to the invention may also have the optional features listed below, considered alone or in combination:

[0018] - the microstructure of the powder particles comprises 3.0 to 95 wt. % ferrite and up to 5 wt. % Ti(C,N), and optionally up to 1.0 wt. % kappa carbides (Fe,Mn) 3 AlCx, the balance is austenite,

[0019] -The density of the powder is less than 7.0g / cm 3 ,

[0020] - the average particle size is between 1 μm and 150 μm,

[0021] - the average particle size is between 1 μm and 20 μm,

[0022] - the average particle size is between 20 μm and 63 μm,

[0023] The average particle size is between 60 μm and 150 μm.

[0024] A second object of the present invention includes a method for producing a metal powder for additive manufacturing, the method comprising:

[0025] -a) melting the elements and / or the metal alloy at a temperature of at least 100° C. above the liquidus temperature to obtain a molten composition according to claim 1,

[0026] - b) atomizing the molten composition with a gas pressurized to 10 to 30 bar through a nozzle having a diameter of at most 4 mm.

[0027] A third object of the invention comprises a method for producing a printed part by additive manufacturing, wherein a powder according to the invention is printed by laser powder bed fusion.

[0028] The printing method according to the present invention may also have the optional features listed below, considered individually or in combination:

[0029] - the method comprises a first step of forming a powder layer having a thickness lower than 100 μm, and a second step of forming a shaped layer by melting at least part of the powder layer with a focused laser beam in an atmosphere consisting essentially of an inert gas,

[0030] -This method is set with the following parameters:

[0031] -Limit laser power to a maximum of 500W,

[0032] - Scanning speed is 300mm / sec to 2000mm / sec,

[0033] - Linear energy density of 190 J / m to 550 J / m,

[0034] - Scanning pitch is 50μm to 150μm,

[0035] - Volume energy density of 100 J / mm3 to 330 J / mm3.

[0036] A fourth object of the invention consists in a printed part obtained according to the invention, the microstructure of which comprises 2.0 to 95% by weight of ferrite and optionally up to 1.0% by weight of kappa carbides (Fe, Mn). 3 AlCx and up to 1 wt% Ti(C,N), the balance being austenite. In a preferred embodiment, the component comprises 2.0 wt% to 90 wt% ferrite, preferably 2.0 wt% to 80 wt% ferrite, and more preferably 2.0 wt% to 50 wt% ferrite. DETAILED DESCRIPTION

[0037] The present invention will be better understood by reading the following description, which is provided for illustrative purposes only and is not intended to be limiting in any way.

[0038] Manganese is present in the composition according to the invention in a content of 15% to 35% by weight. Manganese is an essential alloying element to such an extent, mainly due to the fact that alloying with very large amounts of manganese and carbon stabilizes austenite until room temperature in the final component, and austenite can then tolerate large amounts of aluminum without losing stability and without converting to excessive ferrite or martensite. In order to enable the alloy to have excellent ductility, the manganese content must be equal to or higher than 15% by weight. However, when the manganese content is higher than 35% by weight, the precipitation of the β-Mn phase will deteriorate the ductility of the alloy. Therefore, the manganese content should be controlled to be equal to or greater than 15% by weight, but less than or equal to 35% by weight. In a preferred embodiment, it is equal to or greater than 15.5% by weight or even equal to or greater than 16.0% by weight. Its amount is more preferably 25% to 31% by weight, or even better 26% to 30% by weight.

[0039] Aluminum is present in the composition according to the invention in a content of 6% to 15% by weight. Adding aluminum to high manganese austenitic steel effectively reduces the density of the alloy. In addition, this significantly increases the stacking fault energy (SFE) of austenite in the final component, thereby causing a change in the strain hardening behavior of the alloy. Aluminum is also one of the main elements of nano-sized κ carbides (Fe, Mn) 3AlCx, so its addition significantly enhances the formation of such carbides. On the one hand, in order to ensure austenite stability and the possible precipitation of κ carbides, and on the other hand, in order to control the formation of ferrite, the aluminum concentration of the alloy of the present invention should be adjusted. In addition, it has been observed that an aluminum amount below 6% by weight results in a material density in the final component higher than 7.0 g / cm 3 Therefore, the aluminum content should be controlled to be equal to or greater than 6 wt %, but less than or equal to 15 wt % to avoid removal of the austenite phase. In a preferred embodiment, the aluminum content is 6 wt % to 12 wt %, or even better 6 wt % to 10 wt %.

[0040] The carbon content is set at 0.5 wt. % to 1.8 wt. %. Carbon plays an important role in the formation of the microstructure of the final component. Its main role is to stabilize austenite (which is the main phase of the microstructure of the steel component) and provide strengthening. A carbon content below 0.5 wt. % will reduce the proportion of austenite, which leads to a decrease in both ductility and strength of the alloy. However, since it is a kappa carbide (Fe, Mn) 3 Carbon is the main constituent element of AlCx, so a carbon content above 1.8 wt. % may promote the precipitation of such carbides in a coarse manner on the grain boundaries, which leads to a decrease in the ductility of the alloy.

[0041] Preferably, the carbon content is 0.6 to 1.3 wt%, more preferably 0.8 to 1.2% by weight, in order to obtain sufficient strength.

[0042] Titanium is present in the composition according to the present invention with a content of 0.4 wt % to 4.5 wt %. As will be shown below, it is observed that the addition of at least 0.4 wt % titanium improves the mechanical properties of steel. However, the addition higher than 4.5 wt % results in a complete ferrite microstructure without austenite. The presence of austenite is desirable because it contributes to ductility, strain hardening and toughness characteristics higher than those that can be achieved with ferrite or martensite structures. This is because, unlike in ferritic steels, multiple strengthening mechanisms work in austenitic low-density steels. First, due to a large amount of C and Mn (which have low solubility in ferrite) that are soluble in austenite, thereby causing harmful coarse Mn carbides, solid solution strengthening plays an important role. In addition, strengthening by work hardening is an important mechanism of austenitic steels. A preferred range is 0.5 to 4 wt %, or even better 0.5 to 3 wt % or 1.0 to 3.0 wt %, which allows obtaining a microstructure with an austenite phase as the main phase of the steel. Another preferred range is 2.5 to 4.5 wt % to obtain optimal precipitation of nitrogen-rich Ti(C,N).

[0043] Silicon may be present in the composition according to the invention in a content of 0% to 3.5% by weight. In a preferred embodiment, silicon is added in a content of 1.6% to 3.5% by weight. A preferred range is 1.6% to 2.5% by weight, or even better 1.6% to 2.2% by weight. In another embodiment, the silicon content is limited to 0% to 0.5% by weight. A preferred range is 0.05 to 0.5% by weight, 0% to 0.25% by weight, or even better 0.05% to 0.25% by weight.

[0044] Nickel may optionally be present in an amount up to 8.5 wt %. Nickel may be used as a diffusion barrier for hydrogen. Amounts of nickel above 8.5 wt % are not desirable as they promote the deterioration of (Fe, Mn) 3 The formation of cementite of AlCx carbide.Nickel can also be used as an effective alloying element, because it stabilizes austenite, and also promotes the formation of ordered compounds such as B2 components in ferrite, thereby causing additional strengthening.However, especially for cost reasons, it is desired that the nickel addition be limited to a maximum content of 6.0 wt % or less or 4 wt % or less, and preferably 0.1 wt % to 2.0 wt % or 0.1 wt % to 1.0 wt %.When nickel is not added, the composition may still contain up to 0.1 wt % nickel as an impurity.

[0045] Chromium may optionally be present in an amount of up to 2.5% by weight to increase the strength of the steel by solid solution hardening. It also enhances the high temperature corrosion resistance of the steel according to the invention. However, since chromium reduces the stacking fault energy and stability of austenite, its content must not exceed 2.5% by weight, and is preferably 0.1% to 2.0% by weight or 0.1% to 1.0% by weight. When no chromium is added, the composition may still contain up to 0.1% by weight of Cr as an impurity.

[0046] Boron may optionally be present in an amount of up to 0.1 wt%. Boron has a very low solid solubility and a strong tendency to segregate at grain boundaries, thereby interacting strongly with lattice defects. Boron can therefore serve to limit the precipitation of intergranular kappa carbides.

[0047] Tantalum, zirconium, niobium, vanadium, titanium, molybdenum and tungsten are elements that can optionally be used to achieve hardening and strengthening, in particular by precipitation of nitrides, carbonitrides or carbides. However, when their cumulative amount is above 2.0% by weight, preferably above 1.0% by weight, or even better above 0.5% by weight or above 0.3% by weight, there is a risk that excessive precipitation may cause a reduction in toughness, which must be avoided.

[0048] The balance is made up of iron and the inevitable impurities produced by processing. Phosphorus, sulfur and nitrogen are the main impurities. They are not intentionally added. They may be significantly present in the ferroalloys and / or pure elements used as raw materials. Nitrogen may also be introduced during atomization. It is preferred to control their content to avoid harmful changes in the microstructure and / or to avoid increasing brittleness. Therefore, their content is limited to 0.013 weight %, 0.015 weight % and 0.1 weight % respectively. In a preferred embodiment, their content is limited to 0.005 weight %, 0.015 weight % and 0.05 weight % respectively.

[0049] The microstructure of the powder comprises 3.0 to 95 wt. % ferrite and up to 5 wt. % Ti(C,N), and optionally up to 1.0 wt. % kappa carbides (Fe,Mn). 3 AlCx, the balance being austenite. In a preferred embodiment, the ferrite content may be from 7.0 wt% to 25 wt%. In another preferred embodiment, the microstructure comprises at least 0.3 wt% TiC(N) and less than 0.1 wt% AlN.

[0050] The inventors have observed that when the titanium level increases, the nature of the precipitates present in the powder changes. Above 0.4 wt. %, the powder no longer contains primary aluminum nitride, but only titanium carbonitride. Below 0.4 wt. % titanium, the percentage of primary titanium carbonitride decreases in favor of aluminum nitride.

[0051] The powder can be obtained by first mixing and melting the pure elements and / or ferroalloys as raw materials. It can also be obtained by using a pre-alloyed ingot of the desired composition.

[0052] Ferroalloys refer to various alloys of iron with a high proportion of one or more other elements (e.g. manganese, silicon, aluminum, niobium, boron, chromium, molybdenum, ...). The main alloys are FeMn (usually containing 70-80 wt% Mn), FeAl (usually containing 40-60 wt% Al), FeSi (usually containing 15-90 wt% Si), FeNi (usually containing 70-95 wt% Ni), FeB (usually containing 17.5-20 wt% B), FeCr (usually containing 50-70 wt% Cr), FeMo (usually containing 60-75 wt% Mo), FeNb (usually containing 60-70 wt% Nb), FeV (usually containing 35-85 wt% V), FeW (usually containing 70-80 wt% W).

[0053] The alloying elements can alternatively be added as pure elements (generally with a purity of more than 99% by weight). The pure elements can in particular be carbon and pure metals such as iron, aluminum, manganese or nickel, zirconium, titanium, tantalum, molybdenum, tungsten, niobium, vanadium, chromium.

[0054] A person skilled in the art knows how to mix different ferroalloys and pure elements to achieve a target composition.

[0055] After the composition has been obtained by mixing the pure elements and / or ferroalloys in appropriate proportions, the composition is heated at a temperature of at least 100°C above its liquidus temperature and maintained at this temperature to melt all the raw materials and homogenize the melt. Due to this overheating, the reduction in the viscosity of the molten composition helps to obtain a powder with high sphericity without satellite particles and with an appropriate particle size distribution. That is, since the surface tension increases with temperature, it is preferred not to heat the composition at a temperature of more than 450°C above its liquidus temperature.

[0056] Preferably, the composition is heated at a temperature of at least 200°C above its liquidus temperature to promote the formation of highly spherical particles. More preferably, the composition is heated at a temperature of 250°C above its liquidus temperature.

[0057] In one embodiment of the invention, the composition is heated from 1650°C to 1800°C, which represents a good compromise between viscosity reduction and surface tension increase.

[0058] The molten composition is then atomized into fine metal droplets by forcing the molten metal stream through the orifice of a nozzle at moderate pressure and by impinging it with a gas jet (gas atomization). Just before the metal stream leaves the nozzle, a gas is introduced into the metal stream for generating turbulence when the entrained gas expands (due to heating) and enters a large collection volume (atomization tower). The atomization tower is filled with gas to promote further turbulence of the molten metal jet. The metal droplets cool during their fall into the atomization tower. Gas atomization is preferred because it is conducive to producing powder particles with a high degree of roundness and a low number of satellite particles.

[0059] The atomizing gas is preferably argon or nitrogen or a mixture thereof. Both of them increase the melt viscosity more slowly than other gases such as helium, which promotes the formation of smaller particle sizes. They also control chemical purity, thereby avoiding undesirable impurities, and play a role in the good morphology of the powder. Since the molar weight of nitrogen is 14.01 g / mole, compared with the molar weight of argon is 39.95 g / mole, finer particles can usually be obtained with argon than with nitrogen. On the other hand, the specific heat capacity of nitrogen is 1.04 J / (g K), compared with 0.52 J / (g K) for argon. Therefore, nitrogen increases the cooling rate of the particles.

[0060] Gas pressure is important because it directly affects the particle size distribution. In particular, the higher the pressure, the higher the cooling rate. Preferably, the gas pressure is set to 10 bar to 30 bar, or even better 24 bar to 30 bar, to promote the formation of particles whose size is most compatible with additive manufacturing techniques.

[0061] The nozzle diameter has an influence on the molten metal flow rate and, therefore, on the particle size distribution and on the cooling rate. The nozzle diameter is preferably limited to 4 mm to limit the increase in average particle size and the decrease in cooling rate.

[0062] The metal powder obtained by atomization can be used as is, or can be sieved to retain particles whose size is better suited to additive manufacturing techniques for later use. For example, in the case of additive manufacturing by powder bed fusion, the range 20 μm to 63 μm (called fraction F2) is preferred, and the range 20 μm to 40 μm is even better. In the case of additive manufacturing by laser metal deposition or direct metal deposition, the range 60 μm to 150 μm (called F3) is preferred, and the range 40 μm to 125 μm is even better. Fraction F1 covering particle sizes below 20 μm or even 10 μm can be used, for example, in binder jetting.

[0063] Components made of metal powder according to the present invention can be obtained by additive manufacturing techniques such as: Powder Bed Fusion (LPBF), Direct Metal Laser Sintering (DMLS), Electron Beam Melting (EBM), Selective Heat Sintering (SHS), Selective Laser Sintering (SLS), Laser Metal Deposition (LMD), Direct Metal Deposition (DMD), Direct Metal Laser Melting (DMLM), Direct Metal Printing (DMP), Laser Cladding (LC), Binder Jetting (BJ), Cold Spray (CS), Thermal Spray (TS), High Velocity Oxygen Fuel (HVOF).

[0064] In particular, the present invention can utilize the LPBF method, which is a layer-upon-layer additive manufacturing technique. A thin layer of metal powder is evenly distributed onto a substrate platform, typically metal, using a coating mechanism, which is fixed to an indexing table that moves along a vertical axis. This occurs inside a chamber containing a strictly controlled atmosphere. After the individual layers have been distributed, the 2D slices of the component geometry are fused by selectively melting the powder. This is achieved with a high-power laser beam, typically an ytterbium fiber laser. The laser energy is strong enough to allow the particles to be completely melted (welded) in the form of tracks or strips. Basically, after completing one track, the process is repeated with the next track, which is separated from the first track by a scan pitch. The process is repeated layer by layer until the part is completed. Overhanging geometries are supported by unmelted powder from the previous layer. The main process parameters used in LPBF are typically layer thickness, scan pitch, scan speed and laser power. After completing the process, the remaining powder is screened for reuse.

[0065] The method for producing an additively manufactured component by LPBF comprises a first step of forming a powder layer with a powder according to the invention. Preferably, the powder layer is less than 100 μm. Above 100 μm, the laser may not be able to melt the powder in all layer thicknesses, which may lead to pores in the component. Preferably, the layer thickness is kept between 20 μm and 60 μm to optimize the melting of the powder.

[0066] In a second step, the focused laser beam forms a shaped layer by melting at least part of the powder layer under process conditions detailed below.

[0067] In the case of LPBF, the individual layers of the printed component are at least partially melted in an atmosphere consisting essentially of an inert gas.

[0068] The laser power is preferably limited to a maximum of 500 W. Preferably, the laser power is set above 80 W to facilitate melting in all layer thicknesses. In a preferred embodiment, the laser power is between 175 W and 300 W.

[0069] The scanning speed is preferably 300 mm / sec to 2000 mm / sec, and more preferably 300 mm / sec to 700 mm / sec. Below 300 mm / sec, the excess energy provided by the laser may result in keyhole voids and / or spatters that, if not properly dragged outside the powder bed, are deposited on the powder layer, which creates voids in the printed part. Above 2000 mm / sec, the energy provided by the laser to the powder may be insufficient to melt the powder in all layer thicknesses.

[0070] The Linear Energy Density (LED) is preferably between 190 J / m and 550 J / m. LED is defined as the ratio between the laser power and the scan speed expressed in m / sec. Below 190 J / m, the LED may not be sufficient to properly print the part (due to lack of fusion). Above 400 J / m, the excess energy provided by the laser may result in keyhole voids and spatter that, if not properly dragged outside the powder bed, will deposit on the powder layer. Such deposits create voids in the printed part.

[0071] The scanning pitch is preferably 50 μm to 150 μm. Below 50 μm, individual points of the printed part may re-melt multiple times, which may cause overheating. Above 120 μm, unmelted powder may be trapped between two tracks. More preferably, the scanning pitch is 70 μm to 110 μm.

[0072] The volumetric energy density (VED) is preferably 100 J / mm 3 Up to 330J / mm3 VED is defined as P / (v·h·l t ), where P is the laser power, v is the scanning speed, h is the scanning distance, and l t is the powder layer thickness.

[0073] Example

[0074] The following examples and tests presented hereinafter are non-limiting in nature and must be considered for illustrative purposes only. They will illustrate the advantageous features of the present invention, the importance of the parameters selected by the inventors after extensive experimentation, and further determine the properties that can be achieved by the metal powder according to the present invention.

[0075] Different metal compositions as described in Table 1 were first obtained by mixing and melting ferroalloys and pure elements.

[0076] Table 1

[0077] powder Mn (wt%) Al (wt%) C (weight %) Si (wt%) Fe 1 28 7 0.8 <![CDATA[ 0 ]]> margin 2 28 7 0.8 <![CDATA[ 0.2 ]]> margin <![CDATA[3 ＊ ]]> 28 7 0.8 0.5 margin <![CDATA[4 ＊ ]]> 28 7 0.8 1.0 margin <![CDATA[5 ＊ ]]> 28 7 0.8 2.0 margin <![CDATA[6 ＊ ]]> 28 7 0.8 4.0 margin

[0078] *According to the invention

[0079] P, S and N were kept below 0.013 wt%, 0.015 wt% and 0.1 wt%, respectively.

[0080] These metal compositions were heated up to 1800°C (i.e. 200°C to 350°C above the liquidus temperature) and then gas atomized with nitrogen under the following process conditions:

[0081] - Gas pressure: 20 bar

[0082] -Nozzle diameter: 2.5mm to 3mm.

[0083] The powders were then sieved and classified into fractions F1 to F3. They were evaluated for flowability, sphericity and roundness and were found to be satisfactory for additive manufacturing purposes. The density of the powders was about 6.9 g / cm 3 .

[0084] For powders 1, 2 and 3, the microstructure of the F2 fraction was determined by XRD and is summarized in Table 2.

[0085] Table 2

[0086]

[0087] *According to the invention

[0088] The F2 fraction of such powder was then used to print a series of 22 1 cm3 The cube:

[0089] -Laser power 150W to 200W,

[0090] - Scanning speed 300mm / sec to 1100mm / sec,

[0091] - Scanning pitch 70μm to 110μm,

[0092] - layer thickness 20 μm to 40 μm,

[0093] -Linear energy density (LED) 180J / m to 500J / m,

[0094] -Volume Energy Density (VED) 100J / mm 3 Up to 330J / mm 3 .

[0095] For powders 1, 2 and 3, the microstructure of the printed cubes was determined by XRD and is summarized in Table 3.

[0096] Table 3

[0097]

[0098] *According to the invention

[0099] The microstructure of the printed cubes using Powder 3 was observed by scanning electron microscopy and showed the presence of nano-sized titanium carbides causing grain refinement of the structure.

[0100] Cubes made from powders 1 and 2 contained AlN in an amount less than 1 wt %, whereas cubes made from powders 3, 5, and 6 did not contain any AlN.

[0101] Following the ASTM E112-10 standard, the average grain sizes of the printed cubes using powders 1, 2, and 3 were measured by EBSD patterns using the intercept method to be approximately 30 μm, 30 μm, and 2 μm, respectively.

[0102] The mechanical properties of the printed cubes corresponding to powders 1, 2 and 3 were evaluated. YS and UTS were evaluated using standard ASTM E8 / E8M small-size rectangular specimens. Hardness was measured according to standard ASTM E92-17. The results of such evaluation are summarized in Table 4:

[0103] Table 4

[0104] powder Hardness (HV) YS(MPa) UTS(MPa) 1 298 579 745 2 309 ne ne <![CDATA[3 ＊ ]]> 348 716 932

[0105] ne: not evaluated

[0106] All mechanical properties of the samples according to the invention show a significant improvement with respect to the reference sample, due to the addition of sufficient amounts of titanium to the composition.

Claims

1. A metal powder for additive manufacturing, wherein the composition of the metal powder for additive manufacturing comprises the following elements, expressed in terms of content by weight: 15%≤Mn≤35% 6％≤Al≤15％ 0.5％≤C≤1.8％ 0.4%≤Ti≤4.5% 0≤Si≤3.5% P≤0.013％ S≤0.015％ N≤0.100％ and optionally comprising: - Ni≤8.5 wt.-% and / or Cr≤2.5 wt.-% and / or B≤0.1 wt.-% and / or one or more elements selected from Ta, Zr, Nb, V, Mo and W in a cumulative amount of up to 2.0 wt.-%, The balance is iron and unavoidable impurities resulting from processing.

2. The metal powder according to claim 1, wherein the microstructure of the powder particles comprises 3.0 wt.% to 95 wt.% ferrite and up to 5 wt.% Ti(C,N), and optionally up to 1.0 wt.% kappa carbide (Fe,Mn)3AlCx, with the balance being austenite.

3. A metal powder according to any one of claims 1 or 2, wherein such powder comprises at least 0.3 wt. % TiC(N) and less than 0.1 wt. % AlN.

4. The metal powder according to any one of claims 1 to 3, wherein the titanium content is 0.5 to 3% by weight.

5. The metal powder according to any one of claims 1 to 3, wherein the density of the metal powder is lower than 7.0 g / cm 3 .

6. The metal powder according to any one of claims 1 to 3, wherein the average particle size is between 1 μm and 150 μm.

7. The metal powder according to claim 4, wherein the average particle size is between 1 μm and 20 μm.

8. The metal powder according to claim 4, wherein the average particle size is between 20 μm and 63 μm.

9. The metal powder according to claim 4, wherein the average particle size is between 60 μm and 150 μm.

10. A method for producing a metal powder for additive manufacturing, comprising: -a) melting the elements and / or the metal alloy at a temperature of at least 100° C. above the liquidus temperature to obtain a molten composition according to claim 1, - b) atomizing the molten composition through a nozzle with a gas pressurized to 10 to 30 bar.

11. A method for producing a printed component by additive manufacturing, wherein a powder according to any one of claims 1 to 9 or a powder obtained according to claim 10 is printed by laser powder bed fusion.

12. Method according to claim 11, comprising a first step of forming a powder layer with a thickness lower than 100 μm, and a second step of forming a shaped layer by melting at least part of the powder layer with a focused laser beam in an atmosphere consisting essentially of an inert gas.

13. The method according to any one of claims 11 or 12, wherein: -Limit laser power to a maximum of 500W, - Scanning speed is 300mm / sec to 2000mm / sec, - Linear energy density from 190 J / m to 5500 J / m, - Scanning pitch is 50μm to 150μm, -Volume energy density is 100J / mm 3 Up to 330J / mm 3 .

14. A printed part obtained by the method according to any one of claims 11 to 13, the microstructure of the printed part comprising 2.0 wt% to 95 wt% ferrite, and optionally up to 1.0 wt% kappa carbides (Fe,Mn)3AlCx and up to 1 wt% Ti(C,N), the balance being austenite.

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