Ferromagnetic powder mixture with increased ejection energy

Abstract

A ferromagnetic powder composition comprising: a) a first type of soft magnetic iron-based core particles, where the surface of each core particle is at least partially covered by a coating which is in direct contact with the surface, and b) a second type of soft magnetic iron-based core particles, wherein the material composition of the first and second types of soft magnetic iron-based core particles is different, wherein the hardness of the second type of soft magnetic iron-based core particles is higher than the hardness of the first type of soft magnetic iron-based core particles, and wherein the second type of soft magnetic iron-based core particles makes up 1 to 9 wt%, preferably 2-8 wt%, more preferably 3-7 wt% such as 4-6 wt%, most preferably 5 wt%, of the total amount of the first and second type of soft magnetic iron-based core particles. An object and method are also provided.

Description

[0001] FERROMAGNETIC POWDER MIXTURE WITH INCREASED EJECTION ENERGY

[0002] Technical field

[0003] The technology proposed herein relates generally to the field of ferromagnetic powder mixtures comprising soft magnetic iron-based core particles and methods for producing ferromagnetic powder mixtures.

[0004] Backaround

[0005] Ferromagnetic powder mixtures and composition include soft magnetic composite (SMC) powders which comprise soft magnetic core particles, usually iron-based, with an electrically insulating coating on each particle. Such powders may be used to obtain soft magnetic components or parts, such as by compacting the powders into the desired shape. These components or parts, also known as soft magnetic composites, may be used as an alternative to laminated steel components in electric motors, generators, electromagnets in a wide range of applications.

[0006] For the compaction, a lubricant, particularly a particulate lubricant, is included in the ferromagnetic powder, and the powder is then placed in a preheated die and compacted at a pressure of for example 800 MPa.

[0007] The key characteristics of a ferromagnetic powder and a corresponding component made from such particles are the magnetic properties including the magnetic permeability (p), i.e. the ability to become magnetized or to carry a magnetic flux with the maximum permeability (pmax) defined as the highest value of B / H, i.e. the ratio of the magnetizing force B or field intensity to the induced magnetic flux H, and the hysteresis loss (DC-loss) which is related to the necessary expenditure of energy to overcome the retained magnetic forces within the part made from the soft magnetic core particles and is influenced by the retentivity, or remanence BR, and the coercivity Hc.

[0008] For optimum magnetic properties it is generally desired to maximize the quality and purity of the soft magnetic core particles, and to also maximize the content of the soft magnetic core particles in relation to other components of the ferromagnetic powder, such as the lubricant.

[0009] Optimization of magnetic properties by increasing the content of the soft magnetic core particles in relation to other components of the ferromagnetic powder may however negatively affect other properties of the ferromagnetic powder and components produced therefrom. In particular, the compaction properties may be negatively affected.

[0010] As one example, the ferromagnetic powder should provide a sufficient green strength (GS) to a component produced by compaction, so that the component can be safely handled without risk of breaking in connection with the subsequent heat treatment of the component where a release of stress caused by the compaction shear forces within the component occurs.

[0011] As another example, ferromagnetic powders with soft magnetic core particles are known to stick to, or leave residues on, the compaction die used for the compaction. This may require frequent cleaning or exchange of the die and thus a limitation on the number of components that can be produced using the die before the accumulated powder residues on the die causes an unacceptable low quality and surface smoothness on the produced component. Increasing the amount of lubricant in the ferromagnetic powder can to some extent mitigate the problem of accumulated powder residues as it decreases the ejection energy needed to eject the compacted component from the die, however, increasing the amount of lubricant decreases the content of the soft magnetic core particles and thus leads to diminished magnetic properties.

[0012] EP 2 252 419 B1 generally discloses a ferromagnetic powder composition comprising soft magnetic iron-based core particles, wherein the surface of the core particles is provided with a first inorganic insulating layer and at least one metal-organic layer, located outside the first layer.

[0013] US 10,741 ,316 generally discloses a ferromagnetic powder composition including soft magnetic iron-based core particles, wherein the surface of the core particles is coated with at least one phosphorus-based inorganic insulating layer and then at least partially covered with metal-organic compound(s).

[0014] EP 3 411 169 B1 generally discloses a powder mixture comprising phosphorous coated iron alloy particles and phosphorous coated iron particles.

[0015] EP 3 576 110 A1 discloses a composition comprising particles A having a soft magnetic iron-based core and particles B having a Fe-Si alloy core. US 14 / 110,418 discloses a composite iron-based powder mix comprising iron alloy particles and atomized iron particles.

[0016] Despite the advantages brought about by the technology described in the above cited prior art documents, there remains a need to provide ferromagnetic powder compositions and mixtures which have improved compaction properties while balancing the magnetic properties.

[0017] A primary object of the technology proposed herein is to provide ferromagnetic powder mixtures comprising soft magnetic core particles and having improved compaction properties.

[0018] A further object of the technology proposed herein to provide ferromagnetic powder mixtures comprising soft magnetic core particles and providing an improved balance between two or more of electrical, magnetic and structural properties.

[0019] A further object of the technology proposed herein is to provide a method of producing the powder mixtures comprising soft magnetic core particles.

[0020] Yet a further object of the technology proposed herein is to provide a method of manufacturing an object from the ferromagnetic powder mixtures.

[0021] Further objects of the technology proposed herein encompass an object manufactured from the ferromagnetic powder mixtures and an object comprising a compacted ferromagnetic powder mixture.

[0022] At least one of the above-mentioned objects or at least one of the further objects which will become evident from the below description, are according to first aspect of the technology proposed herein achieved by a ferromagnetic powder composition comprising: a) a first type of soft magnetic iron-based core particles, where the surface of each core particle is at least partially covered by an electrically insulating coating which is in direct contact with the surface, and b) a second type of soft magnetic iron-based core particles, wherein the material composition of the first and second types of soft magnetic iron-based core particles is different, wherein the hardness of the second type of soft magnetic iron-based core particles is higher than the hardness of the first type of soft magnetic iron-based core particles, wherein the second type of soft magnetic iron-based core particles makes up 1 to 9 wt%, preferably 2-8 wt%, more preferably 3-7 wt% such as 4-6 wt%, most preferably 5 wt%, of the total amount of the first and second type of soft magnetic iron-based core particles, and wherein at least 80 wt%, more preferably at least 90 wt% such as at least 99 wt%, based on the total weight of the core particles, of the core particles of the first type of soft magnetic iron-based core particles are in the range 45-150 pm as measured according to ISO 4497.

[0023] At least one of the above-mentioned objects or at least one of the further objects which will become evident from the below description, are according to a second aspect of the technology proposed herein achieved by a method of manufacturing an object from the ferromagnetic powder composition according the first aspect of the technology proposed herein, comprising the steps of:

[0024] (i) compacting the ferromagnetic powder composition according to the first aspect of the technology proposed herein in a die at a compaction pressure in the range of 300-2000 MPa, preferably 400-1200 MPa, to obtain the object,

[0025] (ii) ejecting the object from the die, and

[0026] (iii) optionally heat treating the object in a nonreducing atmosphere, preferably comprising 0-22 wt%, more preferably 0.5 to 2 wt% oxygen (O2) at a temperature in the range of 300-800 °C, preferably 400-750 °C, more preferably 600-700 °C, such as 670-700 °C or 680-700 °C.

[0027] At least one of the above-mentioned objects or at least one of the further objects which will become evident from the below description, are according to a third aspect of the technology proposed herein achieved by an object comprising a compacted ferromagnetic powder composition according to the first aspect of the technology proposed herein.

[0028] Brief description of the drawings

[0029] Figs. 1 A-1 D show photographs of the final two test objects (cylinders) of a manufacturing run (100 objects each) performed using compaction of a reference ferromagnetic powder composition comprising only the first type of soft magnetic iron-based core particles in a die preheated to 45° (1 A, 1C) or 60° (1 B, 1 D) and with either 0.4 wt% amide wax lubricant (1 A, 1 B) or 0.5 wt% amide wax lubricant (1 C, 1 D) included in the ferromagnetic powder composition.

[0030] Figs 1 E-F show photographs of the final two test objects in a manufacturing run (100 objects each) as for Fig. 1 A-1 D, but where the ferromagnetic powder composition also comprised the second type of soft magnetic iron-based core particles, in this case made of FeSi alloy, at a content of 5 wt%, and with 0.4 wt% amide wax lubricant and using a die preheated to 45° (1 E) or 60° (1 F).

[0031] Fig 1G shows photographs of the final two test objects in a manufacturing run (50 objects) as for Figs 1 E-1 F, but with 0.5 wt% amide wax lubricant and using a die preheated to 60°.

[0032] Figs 1 H-11 show photographs of the final two test objects in a manufacturing run (20 objects each) as for Figs 1 A-1 D, but where the ferromagnetic powder composition comprised the second type of soft magnetic iron-based core particles at a content of 2.5 wt% (1 H) or 7.5 wt% (11), and with 0.5 wt% amide wax lubricant and using a die preheated to 60°.

[0033] Fig. 2 shows a graph of the ejection energy for the test run resulting in the final two test objects shown in Fig. 1 F vs 1 B.

[0034] Figs. 3A-3B show photographs of the final test object in manufacturing runs (5 objects each) performed using compaction of either a ferromagnetic powder comprising the first type of soft magnetic iron-based core particles and 5 wt% of the second type of soft magnetic iron-based core particles (3A), or only the first type of soft magnetic iron-based core particles (3B) with a die at room temperature (left object in each Fig.) or preheated to 60°C (right object in each Fig.)

[0035] Detailed description

[0036] The first aspect of the technology proposed herein relates to a ferromagnetic powder composition comprising: a) a first type of soft magnetic iron-based core particles, where the surface of each core particle is at least partially covered by an electrically insulating coating which is in direct contact with the surface, and b) a second type of soft magnetic iron-based core particles, wherein the material composition of the first and second types of soft magnetic iron-based core particles is different, wherein the hardness of the second type of soft magnetic iron-based core particles is higher than the hardness of the first type of soft magnetic iron-based core particles, wherein the second type of soft magnetic iron-based core particles makes up 1 to 9 wt%, preferably 2-8 wt%, more preferably 3-7 wt% such as 4-6 wt%, most preferably 5 wt%, of the total amount of the first and second type of soft magnetic iron-based core particles and wherein at least 80 wt%, more preferably at least 90 wt% such as at least 99 wt%, based on the total weight of the core particles, of the core particles of the first type of soft magnetic iron-based core particles are in the range 45-150 pm as measured according to ISO 4497.

[0037] Accordingly, the technology proposed herein is based on the realization by the present inventors that a low amount of a harder second type of soft magnetic iron-based core particles provides a polishing or cleaning effect of the die used during the compaction of the ferromagnetic powder composition, and that accordingly this polishing or cleaning effect provides for producing longer manufacturing runs of objects without the need for cleaning or exchanging the die. This is for example shown in example 1 and Fig. 2 showing the near-constant ejection energy during a 100-object manufacturing run. In particular as also shown in example 1 and example 2, these low amounts of the second type of soft magnetic iron-based core particles are accompanied by only a negligible diminishing, and in some cases an improvement, in magnetic, electric, and or structural properties of the objects produced from the ferromagnetic powder. In addition, as shown in Example 3 and Figs 3A-3B, the ferromagnetic powder composition of the first aspect of the technology proposed herein provides superior surface finish already for short runs, e.g. 5-objects, compared to the reference ferromagnetic powder composition.

[0038] The first type of soft magnetic iron-based core particles comprises or consists of iron or an alloy of iron comprising at least 90% iron, preferably at least 99% iron, more preferably at least 99.5% iron. Preferably the soft magnetic iron-based core particles are made of essentially pure iron, i.e., iron with inevitable impurities.

[0039] Preferably at least 80 wt%, more preferably at least 90 wt%, of all of the soft magnetic iron-based core particles have a diameter in the range 45-380 pm, measured according to ISO 4497.

[0040] For low to medium frequency applications, such as electric motors, generators, and converters, at least 80 wt%, more preferably at least 90 wt% such as at least 99 wt%, based on the total weight of the core particles, of the core particles are in the range 45- 150 pm (100 mesh corresponding to a D5o of approximately 95-100 pm), as measured according to ISO 4497. Expressed differently at least 80 wt%, more preferably at least 90 wt% such as at least 99 wt%, based on the total weight of the core particles, of the core particles have a diameter in the range 45-150 pm (100 mesh corresponding to a D50 of approximately 95-100 pm), as measured according to ISO 4497.

[0041] For example, preferably at least 80 wt%, more preferably at least 90 wt%, such as at least 99 wt%, based on the total weight of the core particles, of the core particles may be, i.e. have a diameter, in the range 75-150 pm as measured according to ISO 4497.

[0042] Further possible ranges include 45-140 pm, 45-120 pm, 45-100 pm, such as 45-75 pm, as well as 60-150 pm, such as 60-140 pm, 75-120 pm, or 75-100 pm.

[0043] For low frequency applications, such as electric motors, preferably at least 80 wt%, more preferably at least 90 wt% such as at least 99 wt%, based on the total weight of the core particles, of the core particles are in the range 75-380 pm (40 mesh corresponding to a D50 of approximately 180-210 pm), as measured according to ISO 4497.

[0044] The soft magnetic iron-based core particles may be spherical or irregular shaped, irregular shaped particles being preferred. The AD (apparent density) may be between 2.8 and 4.0 g / cm3, preferably between 3.1 and 3.7 g / cm3.

[0045] The soft magnetic iron-based core particles may be water atomized, gas atomized or a sponge iron powder.

[0046] The electrically insulating coating is at least partially covering the surface of each core particles and is in direct contact with the surface of the core particles. Preferably the electrically insulating coating covers all of the surface of at least 50 wt%, such as at least 75 wt% of the core particles. More preferably, the electrically insulating coating covers all of the surface of at least 90 wt%, such as at least 95 wt% of the core particles.

[0047] In direct contact with the surface means that there is no other coating applied between the electrically insulating coating and the surface of the soft magnetic iron-based core particles.

[0048] Typically, the electrically insulating coating has a thickness of about 20-200 nm with a permeability of about 400-600. The thickness of the electrically insulating coating may be estimated from the permeability where a maximum relative magnetic permeability of about 3000 correspond to zero thickness and a maximum relative magnetic permeability of about 700 corresponds to a thickness of about 30 nm for 40 mesh core particles.

[0049] The electrically insulating coating is a coating having a higher resistivity to electrical current than the material of the soft magnetic iron-based core particles. The resistivity may for example be measured using a 4-point test at 0.001 A and 5 mm distance on the as- ejected green parts along the ejection direction. The resistivity of an object manufactured by compacting the first type of soft magnetic iron-based core particles may for example be at least 200 p m, at least pQm Ohm, or at least 400 p m or higher.

[0050] The addition of the second type of soft magnetic iron-based core particles has a polishing effect of the compacting die. This results in a shinier ejected surface of the compacted parts. The reason is suggested to be an effect of the die polishing as there will be less build-up of organic residues and abrasive adhesives (coating and iron debris) that may have a negative impact on the surface of the ejected, i.e. produced part.

[0051] In particular, it appears that the polishing or cleaning effect on the die that the second type of soft magnetic iron-based core particles provide, and the corresponding shinier surface of the compacted parts, corresponds to the surface of the compacted part, and in particular the coating on the first type of soft magnetic iron-based core particles at the surface being less affected by the die.

[0052] In other words, by the polishing or cleaning effect on the die, the electrically insulating coating of the core particles at the surface is more intact, which may provide a higher resistivity of the surface of the compacted part. This is in contrast to the case where the die becomes fouled by deposits of core particles and these deposits of core particles have an abrasive effect on the first type of soft magnetic iron-based core particles at the surface of the part, thus damaging the coating of the first type of soft magnetic iron-based core particles at the surface of the part. This may for example lead to a lower resistivity of the surface.

[0053] The second type of soft magnetic iron-based core particles may have the same particle size as the first type of soft magnetic iron-based core particles. Alternatively, the second type of soft magnetic iron-based core particles may have a smaller particle than the first type of soft magnetic iron-based core particles. A smaller particle size may help with the distribution of the second type of soft magnetic iron-based core particles in the first type of soft magnetic iron-based core particles, and thereby help ensure that the second type of soft magnetic iron-based core particles is present at all parts of the surface of an object formed by compacting the ferromagnetic powder composition to improve the polishing or cleaning effect on the die.

[0054] Preferably the second type of soft magnetic iron-based core particles need not comprise a coating due to the low amount, and / or due to a higher inherent resistivity in the material of the second type of soft magnetic iron-based core particles. However, as described further below, the second type of soft magnetic iron-based core particles may also be coated. The material composition of the first and second types of soft magnetic iron-based core particles is different. In other words, the first and second types of soft magnetic iron-based core particles are made from different material. This may be simply implemented by using an alloy of the material used in the first type of soft magnetic iron-based core particles as the material in the second type of soft magnetic iron-based core particles.

[0055] The hardness of the second type of soft magnetic iron-based core particles is higher than the hardness of the first type of soft magnetic iron-based core particles. In other words, the second type of soft magnetic iron-based core particles is harder than the first type of soft magnetic iron-based core particles. The harder second type of soft magnetic ironbased core particles can thus provide the polishing or cleaning effect when compacted in the die. Further, the harder second type of soft magnetic iron-based core particles can also provide a smoother surface to the object produced by compacting the ferromagnetic powder composition.

[0056] Generally, the hardness of the second type of soft magnetic iron-based core particles should be at least 10%, preferably at least 50%, more preferably at least 100%, (i.e. double) the hardness of the first type of soft magnetic iron-based core particles. The second type of soft magnetic iron-based core particles makes up 1 to 9 wt%, preferably 2-8 wt%, more preferably 3-7 wt% such as 4-6 wt%, most preferably 5 wt%, of the total amount of the first and second type of soft magnetic iron-based core particles. In other words, the content of the second type of soft magnetic iron-based core particles is relatively low in comparison to the content of the first type of soft magnetic iron-based core particles. This relatively low content has surprisingly been shown to provide the desired polishing or cleaning effect, while being low enough so as to not lead to significantly diminished magnetic and electrical properties for objects manufactured using the ferromagnetic powder composition.

[0057] Preferably the hardness of the second type of soft magnetic iron-based core particles, preferably expressed as the Vickers Pyramid Number (HV), preferably HV10, is at least 150%, more preferably at least 250%, most preferably at least 400%, of the hardness of the first type of soft magnetic iron-based core particles.

[0058] Generally, the higher the hardness of the second type of soft magnetic iron-based core particles, the better the polishing or cleaning effect of the die.

[0059] As an example, pure iron (Fe) has a hardness of about 100HV10, where the 10 indicates the weight used to perform the measurement. Thus, as an example, pure iron, i.e. iron with inevitable impurities, with a hardness of 100HV10 may be used as the material for the first type of soft magnetic iron-based core particles. The second type of soft magnetic iron- based core particles should then have a hardness of at least 150HV10, more preferably a least 250HV10, and most preferably at least 400HV10. Examples of the material suitable for the second type of soft magnetic iron-based core particles thus include FeSi with a hardness of about 180HV10 to 190HV10 at 3 wt% Si, 260HV10 to 280HV10 at 4.5 wt% Si, and about 400HV10 to 420HV10 at 6.5 to 6.8 wt% Si. Other useable alloys for the second type of soft magnetic iron-based core particles include Sendust (Fe9.5Si5.5AI) with a hardness of at least about 700HV10, as well as other variants of alloys of Fe, Si and Al.

[0060] Additionally, nonannealed pure iron, i.e. non-alloyed iron, i.e. iron as atomized, can be used for the second type of soft magnetic iron-based core particles as the nonannealed pure iron, with its significant content of oxygen (about 0.9 wt%) and carbon (about 0.4 wt%) provide a relatively hard material with hardness values of 500HV10 to 700HV10. Determining the hardness of a material according to the Vickers Pyramid Number (HV) is done using ISO 6507-1 to ISO 6507-4 and / or by ASTM E384.

[0061] Preferably the soft magnetic iron-based core particles of the first type of soft magnetic iron-based core particles consist of iron and inevitable impurities, and the soft magnetic iron-based core particles of the second type soft of magnetic iron-based core particles comprise Fe and at least one alloying element, preferably at least one of Si, Al, P, Ni, and Co.

[0062] This is advantageous in that the pure iron with inevitable impurities provide the best magnetic properties, while alloys of Fe provide many different possibilities for the second type of soft magnetic iron-based core particles.

[0063] Examples of alloys of Fe and Si include FeSi with 3 to 7 wt% Si.

[0064] Examples of alloys of Fe and P include FeP with 2-5 wt% P.

[0065] Additional examples of alloys include alloys of Fe, Si and Al, e.g. FeSiAl (Sendust).

[0066] Preferably the soft magnetic iron-based core particles of the second type soft of magnetic iron-based core particles comprises, preferably consists of, an alloy of Fe and Si, wherein the alloy of Fe and Si preferably comprises at least 4.5% Si and more preferably at least 6.8% Si.

[0067] FeSi is an advantageous alloy as it has a low cost and has good hardness. Preferably the content of Si may be from 3 to 7 wt%, preferably 3.5 to 6.8 wt%, most preferably 6.8 wt%. In addition, FeSi has similar soft magnetic properties (Msat, Mrem, He) to pure iron (Fe). As an example, the magnetic saturation (Msat) of pure iron is 2.15 T, whereas that of FeSi is 2.0 to 2.1 T, i.e. only a small difference. Accordingly, an FeSi alloy with 6.8 wt% Si is preferred. As an alternative, alloys of FeSiAl provide higher hardness and lower He, but also lesser magnetic saturation values at 1 .0 to 1 .7 T depending on the content of Si and Al. Thus Fe9.5Si5.5AI may have a magnetic saturation of about 1.0 T, while Fe3.5Si3AI may have a magnetic saturation of about 1 .65 T.

[0068] Preferably the soft magnetic iron-based core particles of the second type of soft magnetic iron-based core particles have a D5o measured according to SS-ISO 13320-1 which is less than 75 pm, more preferably less than 45 pm, such as 30 pm, and preferably at least 10 pm.

[0069] Generally, it is preferred to have a small size for the second type of soft magnetic ironbased core particles as may improve the uniform distribution of the second type of soft magnetic iron-based core particles in the first type of soft magnetic iron-based core particles. Particle sizes below D5o of 10 pm may make it more difficult to obtain a uniform distribution.

[0070] Preferably the the second type of soft magnetic iron-based core particles are gas atomized and / or have an apparent density (AD) of at least 3.7 g / cm3, preferably at least 3.9 g / cm3, and / or are spherical.

[0071] Similarly, to a small size for the second type of soft magnetic iron-based core particles, a gas atomized second type of soft magnetic iron-based core particles, and / or a higher apparent density, and / or a high degree of sphericity of the second type of soft magnetic iron-based core particles improve properties of objects manufactured by compacting the ferromagnetic powder composition.

[0072] Generally, it is preferred that the second type of soft magnetic iron-based core particles further have been annealed so as to reach, or approach, a homogenous composition with large grains. This provides a second type of soft magnetic iron-based core particles that has a high hardness and a low He (coercivity).

[0073] The first type of soft magnetic iron-based core particles may have diameters that are at least 75 pm and at the most 300 pm, preferably at least 75 pm and at the most 180 pm. These are suitable diameters for the first type of soft magnetic iron-based core particles. The diameter may be measured according to ISO 4497. Alternatively, the first type of soft magnetic iron-based core particles may be fashioned to have these minimum and maximum diameters by sieving through sieves have apertures corresponding to these values.

[0074] The electrically insulating coating may preferably comprise: (i) a first coating at least partially covering and being in direct contact with the surface of the core particles, the first coating comprising:

[0075] (1) a silicate of the general formula (K2O)a(SiC>2)P, wherein a is moles of K2O, P is moles of SiOa, and the p / a molar ratio is in the interval from 0.5 to 4.1 , (a) wherein the silicate is present in an amount of 0.02 to 1 .0 wt% calculated based on the total weight of the soft magnetic iron-based core particles, and

[0076] (2) optionally particles of a compound comprising bismuth and oxygen having a D50 measured according to SS-ISO 13320-1 in the interval of 0.1 to 10 pm, wherein the first coating further comprises:

[0077] (3) nanoparticles having a D50 measured according to ISO 13320-1 of 10-200 nm, or alternatively having a specific surface area (SSA) of 6-120 m2 / g as determined according to ISO 9277:2022, and optionally:

[0078] (4) a dopant dissolved as an oxo- or hydroxy-anion in the silicate (1 ), and

[0079] (ii) optionally a second coating at least partially covering the surface of the core particles and / or the first coating, the second coating comprising: a. at least one metal-organic compound having the general formula

[0080] R1[(R1)x(R2)y(M)]nOn-l R1( I) or

[0081] R2[M(OH)2(n+1)](n+1)O(n)R2( II) wherein M is selected from the group consisting of Si, Ti, Al, and Zr; O is oxygen; R1is a hydrolysable group; R2is an organic moiety and wherein at least one R2contains at least one amino group; wherein n is the number of repeating units being an integer between 1 and 20; wherein x is 0 or 1 ; and wherein y is 1 or 2, and x+y is 2, wherein the content of the at least one metal-organic compound is 0.05 to 0.40 wt%, preferably 0.10 to 0.30 wt%, based on the total weight of the soft magnetic iron-based core particles.

[0082] Such an electrically insulating coating is advantageous in that it is robust and has good tribological properties making the first type of soft magnetic iron-based core particles more compatible with, i.e. being affected less by, the harder second type of soft magnetic ironbased core particles during the compaction.

[0083] The silicate of the general formula (K2O)a(SiOs)P is a potassium silicate or alternatively named K-silicate, K-waterglass, potassium waterglass or simply herein silicate.

[0084] The p / a molar ratio (i.e., the molar ratio of SiC>2 to K2O) is in the interval from 0.5 to 4.1 . Preferably, the molar ratio p / a is in the interval of 2.0 to 3.75. more preferably the molar ratio p / a is in the interval of 2.5 to 3.5.

[0085] The silicate is present in the amount 0.02 to 1 .0 wt%, more preferably 0.05-0.5 wt% calculated based on the total weight of the first type of soft magnetic iron-based core particles. Preferably, the silicate is present in the amount 0.05-0.2 wt% calculated based on the total weight of the first type of soft magnetic iron-based core particles when at least 80 wt%, based on the total weight of the core particles, of the core particles are 75 pm or more, and 0.1 -0.5 wt% calculated based on the total weight of the first type of soft magnetic iron-based core particles when at least 80 wt%, based on the total weight of the core particles, of the core particles are below 75 pm. The first coating may be applied using an aqueous solution and it has been found that when the soft magnetic iron-based core particles are contacted with such a solution, substantially all of the silicate and all of the other components, such as the particles of a compound comprising bismuth and oxygen, when present, and nanoparticles, when present, end up in the first coating. Accordingly, contents and ratios between components in the aqueous solution and the soft magnetic iron-based core particles carry over to the contents and ratios between components in the first coating and the soft magnetic iron-based core particles.

[0086] The particles of a compound comprising bismuth and oxygen are optional, but it is preferred that they are included, i.e., comprised, in the first coating as they further improve the properties of the glassy coating formed from the silicate and dopant during heat treatment. The particles of a compound comprising bismuth and oxygen, when present, are dispersed in the first coating, e.g., dispersed in the silicate. During and after heat treatment, the particles of a compound comprising bismuth and oxygen react with the silicate and are included in the formed glassy coating.

[0087] The particles of a compound comprising bismuth and oxygen preferably comprise oxides and hydroxides of bismuth. Preferably the D50 measured according to ISO 13320-1 is in the interval of 0.5 to 2 pm.

[0088] Preferably the content of the particles of the compound comprising bismuth and oxygen in the first coating is 0.025-0.3 wt%, preferably 0.05-0.25 wt%, more preferably 0.07-0.22 wt%, such as 0.08-0.22 wt%, such as 0.08-0.11 wt%, based on the total weight of the first type of soft magnetic iron-based core particles.

[0089] The content of 0.08-0.11 wt% is currently the best range for soft magnetic iron-based core particles sized as 100 mesh.

[0090] When the soft magnetic iron-based core particles are larger, e.g., of 40 mesh size, the content of the particles of the compound comprising bismuth is preferably at least 0.05 wt%, such as 0.05-0.10 wt%.

[0091] When the soft magnetic iron-based core particles are smaller, e.g., of 200 mesh size, the content of the particles of the compound comprising bismuth is preferably at least 0.15 wt%, such as 0.15-0.30 wt%.

[0092] The compound comprising bismuth and oxygen may be selected from the group consisting of bismuth(lll) oxide (Bi2C>3) and bismuth(lll) hydroxide (Bi(OH)3), wherein the compound comprising bismuth and oxygen preferably is Bi(OH)3. The presence of Bi2O3or Bi(OH)3particles increase resistivity. Further, the resistivity is increased more for Bi(OH)3particles than for Bi2O3particles.

[0093] The D5O measured according to ISO 13320-1 is defined in ISO 13320-1 as the median particle diameter used on a volumetric basis, i.e. , 50% by volume of the particles is smaller than this diameter and 50% is larger.

[0094] Generally, references herein to ISO-standards are equivalent to references to SS-ISO standards where SS merely indicates that the concerned ISO standard has been adopted as a Swedish standard.

[0095] The D5O measured according to ISO 13320-1 can be determined using e.g., a Mastersizer 3000 from Malvern instruments.

[0096] Preferably the first coating further comprises nanoparticles having a D5o measured according to ISO 13320-1 of 10-200 nm, or alternatively having a specific surface area (SSA) of 6-120 m2 / g as determined according to ISO 9277:2022.

[0097] Inclusion of the nanoparticles further improves resistivity of the glassy coating formed form the first coating and any second coating applied on top thereof. Inclusion of nanoparticles further work well together with the dopant.

[0098] The nanoparticles, when present, are dispersed in the first coating, e.g., dispersed in the silicate. During and after heat treatment, the nanoparticles become embedded in the formed glassy coating.

[0099] The nanoparticles have a D5o measured according to ISO 13320-1 of 10-200 nm. The D50 measured according to ISO 13320-1 is defined in ISO 13320-1 as the median particle diameter used on a volumetric basis, i.e. , 50% by volume of the particles is smaller than this diameter and 50% is larger.

[0100] Generally, references herein to ISO-standards are equivalent to references to SS-ISO standards where SS merely indicates that the concerned ISO standard has been adopted as a Swedish standard.

[0101] The D50 measured according to ISO 13320-1 can be determined using e.g., a Mastersizer 3000 from Malvern instruments.

[0102] An alternative parameter for determining the size of the nanoparticles is the specific surface area (SSA) [m2 / g], i.e., the surface area of the particles per g of particles.

[0103] Accordingly, a D50 measured according to ISO 13320-1 of 10-200 nm may be equivalently replaced by a specific surface area (SSA) in the range of 6-120 m2 / g.

[0104] The SSA for the nanoparticles is preferably determined using the BET-method, which is a method for determination of the specific surface area of solids by gas adsorption.

[0105] More preferably, the SSA for the nanoparticles is preferably determined according to ISO 9277:2022.

[0106] Accordingly, a D50 measured according to ISO 13320-1 of 10-200 nm may be equivalently replaced by a specific surface area (SSA) of 6-120 m2 / g as determined according to ISO 9277:2022.

[0107] Preferably, the specific surface area (SSA) of the nanoparticles is 10-50, more preferably 10-30, most preferably 15-30 m2 / g. One example is 18 m2 / g. As above, these ranges are preferably determined according to ISO 9277:2022.

[0108] The specific surface area may be measured using a Micromeritics TriStar 3000 gas adsorption instrument which calculates the BET surface area.

[0109] For comparison, an average diameter for the nanoparticles may be calculated from the specific surface area if the particles are assumed to be spherical. The equation for calculating the average particle diameter in nanometres is 6000 / (BET surface area in m2 / g) x (density in g / cm3). For Y2O3 (density 5.01 g / cm3), the specific surface areas of 120, 6, 50, 10, and 18 m2 / g respectively yield the average diameters of 10, 200, 24, 120, and 67 nm respectively.

[0110] Preferably, the nanoparticles have a D5o measured according to ISO 13320-1 of 10 -100 nm. Most preferably the nanoparticles have a D5o measured according to ISO 13320-1 of 20-100 nm. The former interval corresponds to a SSA of 12-120 m2 / g, whereas the latter interval corresponds to a SSA of 12-60 m2 / g.

[0111] The D5O measured according to ISO 13320-1 is preferably between 10 and 100 nm, where 90 wt% of the particles shall have maximum diameters between 1 and 500 nm.

[0112] The nanoparticles generally have a D5o of 10 nm, and this size of nanoparticles have been shown to provide the best results.

[0113] Alternatively, the nanoparticles may have diameters of 1 -200 nm, preferably 1 -50 nm, more preferably 5-50 nm, such as 30-50 nm or such as 5-20 nm such as 10 nm.

[0114] The dopant is dissolved as an oxo- or hydroxy anion in the silicate (1). The oxo- or hydroxo-anion may be a mono- or poly-anion, preferably a mono-anion to maximize distribution in the silicate. In addition to improved distribution, the use of a mono-anion may also decrease the risk of an increase of the melting temperature of the glassy coating formed from the first coating, and any second coating applied on top thereof, during the heat treatment. Specifically, it is contemplated that an increase in melting temperature could be caused by the presence of the longer poly-anions competing with the polysilicate ions in the glassy coating. Such an increase in melting temperature could make it more difficult to obtain a good distribution of the glassy coating.

[0115] The dopant being dissolved as an oxo-or hydroxy-anion encompasses that the dopant is an oxo- or hydroxy-anion dopant. The term dopant encompasses both compounds that form an oxo-or hydroxy-anion when dissolved in the silicate or an aqueous solution of the silicate, as well as the oxo-or hydroxy-anions themselves. As the aqueous solution, which contains the silicate, is generally alkaline, the dopant may be a compound that forms oxo- or hydroxy-anions when dissolved in an alkaline aqueous solution.

[0116] Generally, the content of dopant may be from 0.5-30 mol%, preferably 1 -30 mol%, more preferably 1 -25 mol% based on the molar content of K (Potassium) in the first coating.

[0117] The second coating further improves the electrical, structural and magnetic properties of components or parts manufactured from the ferromagnetic powder composition. Without wishing to be bound by theory, it appears that the second coating may provide lubrication and additional silicon and carbon which helps formation of the glassy coating during heat treatment.

[0118] R1may be an alkoxy-group having less than 4, preferably less than 3 carbon atoms. R2is an organic moiety, which means that the R2-group contains an organic part or portion. R2preferably includes 1 -6, more preferably 1 -3, carbon atoms. R2may further include one or more hetero atoms selected from the group consisting of N, O, S and P. The R2group may be linear, branched, cyclic, or aromatic. R2may include one or more of the following functional groups: amine, diamine, amide, imide, epoxy, hydroxyl, ethylene oxide, ureido, urethane, isocyanato, acrylate, glyceryl acrylate, benzyl-amino, vinyl-benzyl-amino. The R2group may vary between any of the mentioned functional R2-groups and a hydrophobic alkyl group with repeatable units.

[0119] When n=1 the metal-organic compound is a monomer (formula I) or a dimer (Formula II). If the metal-organic compound is a monomer it may be selected from the group of trialkoxy and dialkoxy silanes, titanates, aluminates, or zirconates. The monomer of the metal-organic compound may thus be selected from 3-aminopropyl-trimethoxysilane, 3- aminopropyl-triethoxysilane, 3-aminopropyl-methyl-diethoxysilane, N-aminoethyl-3- aminopropyl / ethyl / methyl-alkoxy-silane such as N-aminoethyl-3-aminopropyl- trimethoxysilane and N-aminoethyl-3-aminopropyl-methyl-dimethoxysilane, 1 ,7- bis(triethoxysilyl)-4-azaheptan, triamino-functional propyl-trimethoxysilane, 3-ureidopropyl- triethoxysilane, 3-isocyanatopropyl-triethoxysilane, tris(3-trimethoxysilylpropyl)- isocyanurate, 0-(propargyloxy)-N-(triethoxysilylpropyl)-urethane, 1 -aminomethyl- triethoxysilane, 1-aminoethyl-methyl-dimethoxysilane, or mixtures thereof.

[0120] When n=2-20 the metal-organic compound is an oligomer. An oligomer of the metalorganic compound may be selected from alkoxy-terminated alkyl-alkoxy-oligomers of silanes, titanates, aluminates, or zirconates. The oligomer of the metal-organic compound may thus be selected from methoxy, ethoxy or acetoxy-terminated amino-silsesquioxanes, amino-siloxanes, oligomeric 3-aminopropyl-methoxy-silane, 3-aminopropyl / propyl-alkoxy- silanes, N-aminoethyl-3-aminopropyl-alkoxy-silanes, or N-aminoethyl-3- aminopropyl / methyl-alkoxy-silanes or mixtures thereof.

[0121] Examples of suitable metal-organic compounds in particular include Dynasylan® 1 146 and Dynasylan® SIVO 203 from Evonik Industries AG, or XIAMETER™ OFS-6020 Silane from Dow Chemical Company.

[0122] Water-borne amino- or multifunctional silane systems are also comprised by the metalorganic compound, such as the corresponding Dynasylan® HYDROSIL products supplied by Evonik industries AG. In these products the hydrolysable alkoxy-groups have almost fully been replaced with hydroxyl groups, i.e., as per Formula (II), while the functionality is similar, e.g., hydrophobic alkyl-groups in combination with amino- or diamino-alkyl-groups. Examples include the Dynasylan® HYDROSIL 2627, 2776, and 1151 silane systems. Examples of such compounds can be 1 ,3-Bis(3-aminopropyl)disiloxane-1 ,1 ,3,3-tetrol or (3-aminopropyl)(([(propyl)dihydroxysilyl]oxy})silan ediol. It is further contemplated that a part, or all, of the particles of a compound comprising bismuth and oxygen and having a D50 measured according to ISO 13320-1 in the interval of 0.1 to 10 pm, which are optionally comprised by the first coating, may be provided in the second coating also or instead.

[0123] A variety of metal organic compounds in the second coating can be used successfully in the ferromagnetic powder composition.

[0124] Preferably, the at least one metal-organic compound has the general formula (I). Alternatively, the at least one metal-organic compound has the general formula (II).

[0125] The first coating may be applied using the following method comprising the steps of:

[0126] (i) providing a first type of soft magnetic iron-based core particles,

[0127] (ii) contacting the soft magnetic iron-based core particles with a first aqueous solution comprising: a. a silicate of the general formula (K2O)a(SiO2)P, wherein a is moles of K2O, P is moles of SiO2, and the p / a molar ratio is in the interval from 0.5 to 4.1 , i. wherein the silicate is present in an amount of 0.02 to 1 .0 wt% calculated based on the total weight of the ferromagnetic powder composition, b. optionally, particles of a compound comprising bismuth and oxygen having a D50 measured according to ISO 13320-1 in the interval of 0.1 to 10 pm, c. optionally a dopant dissolved as an oxo- or hydroxy-anion in the silicate (a), d. optionally, nanoparticles having a D50 measured according to ISO 13320-1 of 10-200 nm, or alternatively having a specific surface area (SSA) of 6- 120 m2 / g as determined according to ISO 9277:2022, or

[0128] The method may comprise the following additional steps of:

[0129] (iii) drying the soft magnetic iron-based core particles, and / or

[0130] (iv) contacting the soft magnetic iron-based core particles with at least one metalorganic compound having the general formula

[0131] R1[(R1)x(R2)y(M)]nOn-1 R1(I) or

[0132] R2[M(0H)2(n+1)](n+1)0(n) R2(II) wherein M is selected from the group consisting of Si, Ti, Al, and Zr; O is oxygen; R1is a hydrolysable group; R2is an organic moiety and wherein at least one R2contains at least one nitrogen containing group, preferably an amino group; wherein n is the number of repeating units being an integer between 1 and 20; wherein x is 0 or 1 ; and wherein y is 1 or 2, and x+y is 2, wherein the content of the at least one metal-organic compound is 0.05 to 0.40 wt%, preferably 0.10 to 0.30 wt%, based on the total weight of the ferromagnetic powder composition, and / or

[0133] (v) mixing the soft magnetic iron-based core particles with a lubricant, preferably a particulate lubricant.

[0134] Step (iii) is preferably performed after step (ii). Step (iii) may be performed by heating the soft magnetic iron-based core particles while stirring.

[0135] Step (iv) is preferably performed after step (ii) or (iii), and before step (v).

[0136] Step (v) is preferably performed after step (iii) and step (iv).

[0137] The contacting of the soft magnetic iron-based core particles with the first aqueous solution may be performed by mixing, e.g., in a mixer. The result of contacting the soft magnetic iron-based core particles with the first aqueous solution is that the first coating is formed on the magnetic iron-based core particles so as to at least partially cover the magnetic iron-based core particles. The soft magnetic iron-based core particles coated with the first coating and optionally also coated with the second coating as described below may alternatively be referred to as coated core particles or coated soft magnetic iron-based core particles.

[0138] It may occur that the nanoparticles as provided or obtained are agglomerated into agglomerates having a diameter above 200 nm and / or such that the agglomerated nanoparticles have a D5o above 200 nm. These agglomerates should preferably be fully or partially disintegrated so as to obtain, or increase the number of, nanoparticles having the desired D5o or diameter of 1 -200 nm or smaller as preferred above because well distributed nanoparticles within the first coating is preferred. Where the nanoparticles used in the method comprises significant amounts of agglomerates, and when no further disintegration is performed on the nanoparticles, then the mol% of nanoparticles in the first coating may preferably be increased compared to when nanoparticles comprising no or only a minor number of agglomerates and having a lower D5o or diameter are used.

[0139] The disintegration preferably takes place before or during the preparation of the first aqueous solution, or during the contacting of the soft magnetic iron-based core particles with the first aqueous solution. As an example, sonication may be used for disintegration. Preferably the content of nanoparticles in the first coating is the nanoparticles is 1-30 mol%, preferably 1 -20 mol%, based on the molar content of K (Potassium) in the first coating, and wherein the nanoparticles preferably are selected from the group consisting of Y2O3 nanoparticles, ZrC>2 nanoparticles, ZnO nanoparticles, Mg(OH)2nanoparticles, MgO nanoparticles, CaCOs nanoparticles, AI2O3 nanoparticles, SiC>2 nanoparticles, and TiC>2 nanoparticles, and wherein the nanoparticles more preferably comprise or consist of Y2O3 nanoparticles.

[0140] The inclusion of the nanoparticles in the first coating appears to lead to a more even distribution of the coating over the surface of the core particles. This improves the electrical insulation between the core particles, which lead to a higher resistivity of parts manufactured from the ferromagnetic powder composition.

[0141] The nanoparticles may comprise a mixture of nanoparticles, such as a mixture of two or more of the listed nanoparticles. Presently, preferred is however that only one type of nanoparticles, e.g., preferably Y2O3 nanoparticles, is present in the first coating.

[0142] The dopant is effective with numerous different nanoparticles. Numerous different nanoparticles are effective in obtaining improved magnetic and electric properties for objects manufactured from the ferromagnetic powder composition Y2O3 nanoparticles, also known as yttria nanoparticles and yttrium oxide nanoparticles, provides the currently considered best magnetic and electric properties.

[0143] Preferably, the first coating comprises:

[0144] - 1-25 mol%, more preferably 8-22 mol%, most preferably 10-20 mol%, such as 20 mol% Y2O3 nanoparticles based on the content of K in the first coating, or

[0145] - 1-20 mol%, preferably 1 -15 mol%, more preferably 1-10 mol% such as 5 mol% ZrO2 nanoparticles based on the content of K in the first coating, or

[0146] - 1-20 mol%, preferably 5-20 mol%, more preferably 10-20 mol% Mg(OH)2nanoparticles based on the content of K in the first coating, or

[0147] - 1-20 mol%, preferably 5-20 mol%, more preferably 10-20 mol% CaCOs nanoparticles based on the content of K in the first coating, or

[0148] - 1-20 mol%, preferably 5-20 mol%, more preferably 10-20 mol% ZnO nanoparticles based on the content of K in the first coating, or

[0149] - 1-30 mol%, preferably 10-30 mol%, more preferably 15-25 mol% such as 20 mol% MgO nanoparticles based on the content of K in the first coating, or

[0150] - 1-30 mol%, preferably 10-30 mol%, more preferably 15-25 mol% such as 20 mol% Ti02 nanoparticles based on the content of K in the first coating, or - 1-20 mol%, preferably 5-15 mol%, more preferably 10 mol% AI2O3 nanoparticles based on the content of K in the first coating, or

[0151] - 1-20 mol%, preferably 1 -10 mol%, more preferably 5 mol% ZnO nanoparticles based on the content of K in the first coating.

[0152] These contents of the various nanoparticles give good results. As above, different nanoparticles according to these ranges may be combined in the first coating.

[0153] Preferably the nanoparticles comprise or consist of Y2O3 nanoparticles and the content of nanoparticles in the first coating is 10-20 mol% based on the molar content of K (Potassium) in the first coating.

[0154] Y2O3 nanoparticles provides the currently considered best magnetic and electric properties.

[0155] For reference, 20 mol% Y2O3 particles when included in a first coating comprising 0.1 wt% potassium silicate with a p / a molar ratio of 3.4 on 5 kg of soft magnetic iron-based core particles of the first type corresponds to 0.94 g Y2O3 particles, i.e., 0.0188 wt% based on the weight of the first type of soft magnetic iron-based core particles.

[0156] Preferably the dopant comprises at least one element from group 5, such as V (Vanadium) or Nb (Niobium), or comprises at least one element from group 6, such as Cr (Chromium), W (tungsten), or Mo (Molybdenum), or comprises Al (Aluminium) or P (Phosphorus), and wherein preferably the content of dopant in the first coating is 1-30 mol%, preferably 5-20 mol%, more preferably 5-15 mol% or 1 -3 mol%, based on the molar content of K (Potassium) in the first coating.

[0157] The inclusion of the dopant in the first coating provides improved ageing properties and higher resistivity for a given coercivity level and coating density / thickness level to parts manufactured from the ferromagnetic powder composition. Specifically, these parts can be heat-treated at higher temperatures while at the same time maintaining acceptable electrical resistivity properties. In other words, the inclusion of the dopant in the first coating provides better thermal stability, and / or specific electrical resistivity for a given coercivity level and coating density / thickness level, to the glassy coating that is formed from the first coating, and any second coating applied on top thereof, when the ferromagnetic powder composition has been compacted into a part and heat treated.

[0158] Preferred elements of group 5 include V (Vanadium), Nb (Niobium), and Ta (Tantalum).

[0159] Preferred elements of group 6 include Cr (Chromium), Mo (Molybdenum), and W (tungsten). The group 5 and 6 elements are known to form oxo- or hydroxo-anions in alkaline water solutions. Also, Al (Aluminium) can be dissolved as a hydroxy anion in strong alkaline solutions and thus used as a dopant. Phosphorus in the form of a phosphate, e.g., KHPO4, H3PO4, (NH4)3PO4can also be used. Also Nb and Tantal can form oxo- and / or hydroxo-anions analogously to W, Mo and W.

[0160] Preferred dopants are those that are easily dissolved and stable in the silicate solution. Toxic dopants, such as ions including Cr(VI), are less preferred.

[0161] The dopant is preferably provided to the first coating by dissolving a suitable compound comprising the dopant, such as for example an oxide, in the first aqueous solution that the soft magnetic iron-based core particles is contacted with. This typically leads to the provision of ions of the dopant in the first aqueous solution.

[0162] Preferred elements for the dopant include Al, Nb, V, Mo, Cr. More preferred elements include Al and Nb.

[0163] V, vanadium, is preferably provided to the first coating by dissolving vanadium(V) oxide, V2O5 in the first aqueous solution that the soft magnetic iron-based core particles is contacted with. In strong alkaline water solutions, such as potassium silicate solutions, the vanadium will form predominantly (VC )3' ions (pH>12). This will lead to the provision of VO43' ions in the first aqueous solution. In less strong alkaline environments, the vanadium tends to form polyvanadate ions coordinating more than four oxo- or hydroxo groups, such as (VO3)n‘, analogue to polyphosphate chains. Thus, the size of the vanadate ions may vary dependant on the concentration of potassium and the pH of the silicate solution.

[0164] It is believed that the dopant ion shall preferably not exist as polyanions in the silicate prior to heat treatment in order to maximize the atomic distribution of dopants in the final glassy coating, which may theoretically increase the specific electrical resistivity of the bismuthsilicate glass.

[0165] Mo, molybdenum, is preferably provided to the first coating by dissolving Molybdenum(VI) oxide, M0O3 in the first aqueous solution that the soft magnetic iron-based core particles is contacted with. This will lead to the provision of molybdate ions (M0O42), analogue with the tungstate ions, in the first aqueous solution.

[0166] W, tungsten, is preferably provided to the first coating by dissolving Tungsten(VI) oxide, WO3 in the first aqueous solution that the soft magnetic iron-based core particles is contacted with. This will lead to the provision of tungstate ions (WO42), analogue with the vanadate ions, in the first aqueous solution. Al, Aluminium, is preferably provided to the first coating by dissolving Aluminium(lll) hydroxide, AI(OH)3 in the first aqueous solution that the soft magnetic iron-based core particles is contacted with. This will lead to the provision of AI(OH)4‘ ions in the first aqueous solution.

[0167] Preferably:

[0168] - the dopant comprises V and the content of dopant in the first coating is 1 -30 mol%, preferably 5-20 mol%, more preferably 5-15 mol%, based on the molar content of K (Potassium) in the first coating,

[0169] - the dopant comprises Nb and the content of dopant in the first coating is 1 -30 mol%, preferably 5-20 mol%, more preferably 5-15 mol%, based on the molar content of K in the first coating,

[0170] - the dopant comprises Cr and the content of dopant in the first coating is 1 -30 mol%, preferably 5-20 mol%, more preferably 5-15 mol%, based on the molar content of K in the first coating,

[0171] - the dopant comprises Mo and the content of dopant in the first coating is 1 -30 mol%, preferably 5-20 mol%, more preferably 5-15 mol%, based on the molar content of K in the first coating,

[0172] - the dopant comprises W and the content of dopant in the first coating is 1-30 mol%, preferably 5-20 mol%, more preferably 5-15 mol%, based on the molar content of K in the first coating,

[0173] - the dopant comprises Al and the content of dopant in the first coating is 0.5-5 mol%, preferably 1 -3 mol%, more preferably 1 .71 -2.58 mol% based on the molar content of K in the first coating, and / or,

[0174] - the dopant comprises P and the content of dopant in the first coating is 1 -30 mol%, preferably 5-20 mol%, more preferably 5-15 mol%, based on the molar content of K in the first coating.

[0175] More preferably, the dopant comprises V and the content of dopant in the first coating is 1-30 mol%, preferably 5-20 mol%, more preferably 10-15 mol%, based on the molar content of K in the first coating.

[0176] 10-15 mol% of V dopant yields higher resistivity for a given coercivity level and coating density / thickness level. This is believed to be caused by a better distribution of the glassy coating formed from the first coating, and any second coating on top thereof, during the heat treatment. Alternatively, the dopant comprises Al and the content of dopant in the first coating is 0.5- 5 mol%, preferably 1 -3 mol%, more preferably 1.5-2.7 mol% such as 1.71 -2.58 mol%, based on the molar content of potassium K in the first coating.

[0177] The provision of an Al dopant to the first coating at a concentration in this range allows higher heat treatment temperatures yielding lower coercivity while maintaining good resistivity. The effect is less than for V, but Al has less environmental effect and presents a lesser health risk.

[0178] Preferably the surfaces of each soft magnetic iron-based core particle of the second type of soft magnetic iron-based core particles are at least partially covered by an electrically insulating coating which is in direct contact with the surface.

[0179] This is advantageous in that it further improves the resistivity of objects manufactured from the ferromagnetic powder composition.

[0180] It is preferred that the second and first types of soft magnetic iron-based core particles are coated together, i.e. are mixed and then coated, to provide a better mixing and homogeneity of the ferromagnetic powder composition.

[0181] Preferably: a) the electrically insulating coating on the second type of soft magnetic iron-based core particles comprises a first and second coating as defined above, or b) the electrically insulating coating on the second type of soft magnetic iron-based core particles comprises iron phosphate (FePC ).

[0182] Accordingly, if present, the electrically insulating coating or surface treatment preferably comprises the first, and optionally also the second, coating as described above. The soft magnetic iron-based core particles of the second type may alternatively be coated or treated with another coating, such as by being treated with phosphoric acid diluted in acetone to form iron phosphate (FePC ).

[0183] The ferromagnetic powder composition preferably further comprises a lubricant, preferably a particulate lubricant.

[0184] Including a lubricant in the ferromagnetic powder composition improves compaction and leads to an increased density and strength of an object manufactured from the ferromagnetic powder composition. The lubricant may be selected from the group consisting of primary and secondary fatty acid amides, trans-amides (bisamides) or fatty acid amides or alcohols. The lubricating moiety of the lubricant may be a saturated or unsaturated chain containing between 12-22 carbon atoms. The lubricant may preferably be selected from stearamide, behenyl alcohol, erucamide, stearylerucamide, erucyl- stearamide, behenyl alcohol, erucyl alcohol, ethylene-bisstearamide (i.e., EBS or amide wax). Preferably the lubricant is an amide wax. Preferably the lubricant is also a mixture of stearamide or behenyl alcohol and an amide wax. One example is 0.1 wt% stearamide combined with 0.3 wt% amide wax.

[0185] The lubricant may be present in an amount of 0.05-0.80 wt%, preferably 0.20-0.50 wt% of the ferromagnetic powder composition. If a very low amount of lubricant is added in the composition (0.05 to 0.20 wt%), the compaction and ejection can be facilitated by using die wall lubrication (DWL). The low amount of internal lubricant will improve compact density, permeability and mechanical strength.

[0186] A second aspect of the technology proposed herein relates to a method of manufacturing an object from the ferromagnetic powder composition according to the first aspect of the technology proposed herein, comprising the steps of:

[0187] (i) compacting the ferromagnetic powder composition according to the first aspect of the technology proposed herein in a die at a compaction pressure in the range of 300-2000 MPa, preferably 400-1200 MPa, to obtain the object,

[0188] (ii) ejecting the object from the die, and

[0189] (iii) optionally heat treating the object in a nonreducing atmosphere, preferably comprising 0-22 wt%, more preferably 0.5 to 2 wt% oxygen (O2) at a temperature in the range of 300-800 °C, preferably 400-750 °C, more preferably 600-700 °C, such as 670-700 °C or 680-700 °C.

[0190] The compaction may be cold die compaction, warm die compaction, or high-velocity compaction, preferably a controlled die temperature compaction (45-120°C) with an unheated powder is used. During the compaction, the soft magnetic iron-based core particles are pressed together and deformed so as to adhere to each other and form the compacted part. During the heat treatment the particles of the compound comprising bismuth and oxygen together with the nanoparticles and the silicate in the first coating and the amino and / or alkyl groups of the metal-organic compound of the second coating form an evenly distributed bismuth-silicate glass on the surface of the soft magnetic iron-based core particles which provides the desired electrical resistivity between the individual particles of the compacted and heat treated ferromagnetic powder composition in the finished object. Additionally, the heat treatment relieves the stress formed during the compaction. As seen in the examples, the die may preferably be heated to at least 45°C, more preferably at least 60°C.

[0191] The heat treatment process may be in vacuum, non-reducing, inert or in weakly oxidizing atmospheres, e.g., 0.01 to 3 wt% oxygen in nitrogen. In one embodiment, an essentially pure nitrogen atmosphere is used as a non-reducing atmosphere. In one embodiment with addition of 0-22 wt% oxygen, preferably 0.5-2 wt% oxygen. Higher temperature, above 680-700 °C, may require lower oxygen levels such as 500-3000 ppm (0.05-0.3 wt%). Generally, the oxygen levels may be higher during the initial heating, e.g., delubrication. Optionally, the heat treatment is performed in an inert atmosphere and thereafter exposed quickly in an oxidizing atmosphere, such as 0.5-22 wt% oxygen / nitrogen mixtures or in steam / nitrogen mixtures, to build a superficial crust of higher strength and / or corrosion resistance. The temperature may in one embodiment be up to 800°C. Heat treating the compacted part at a temperature in the range 300-800 °C means that the temperature compacted part is exposed to a temperature in the range 300-800 °C. This is typically done for a time period sufficient to cause the compacted part to be heated to a temperature in the range 300-800 °C, such as for example 20-120 minutes.

[0192] Typically the heat treating is performed in three phases: a delubrication stage at about 300-400°C during which the compacted part is heated up towards the curing stage, a curing stage at about 350-450°C (first temperature and time) in which the first coating is cured so as to cause the formation of the electrically insulating glassy coating (the silicate and any present silane is being polymerised to form the silicate glass) from the first, and second coating, when present, and a relaxation stage at 600-700°C (second temperature and time) in which the glassy coating flows out to cover the core particles and the stresses from the compaction was released. The temperature in the range of 300-800 °C given for step (ii) above corresponds to this last (second) temperature. The first and second time period may typically be 0-60 minutes each, such as 1 -60 minutes.

[0193] The object is further preferably heat treated at a temperature below the glass crystallisation temperature of the first coating. This is because crystallisation of the silicate in the coating layer may decrease the resistivity and mechanical strength of the silicate and the first coating. Further, crystallisation of the silicate in the first coating may cause cracks in the glassy coating formed by the first coating and the second coating during the heat treatment.

[0194] Preferably step (iii) comprises heat treating the compacted part at a (second) temperature of at least 650°C, more preferably at least 670°C to substantially or fully eliminate the stress in the compacted part. The temperature where maximum elimination of stress in the compacted part occurs is called the maximum relaxation temperature.

[0195] For heat treating at higher second temperatures, e.g., between 700°C and 750°C or 750°C and up to 800°C, it is preferred that a thicker first coating, i.e. , a higher wt% of the silicate, such as 0.25 wt%, is used as such thicker coating provide acceptable remaining resistivity while having the potential to provide even better ageing properties. This also applies to ferromagnetic powder mixture comprising harder or alloyed particles which benefit from being treat at these higher second temperatures as that allows a higher degree of relaxation of the comparative less degree of plastic deformation during the compaction. In particular finer powders, e.g., 200-300 mesh, may advantageously be coated with the thicker first coating as the resulting lower permeability is generally acceptable for the type of passive components in which these finer powders are typically used.

[0196] The inclusion of the dopant allows these high heat treatment step temperatures with corresponding low coercivity while maintaining acceptable resistivity and thus acceptable core loss.

[0197] A third aspect of the technology proposed herein relates to an object comprising a compacted ferromagnetic powder composition according to the first aspect of the technology proposed herein.

[0198] A further aspect of the technology proposed herein relates to an object obtained by the method according to the second aspect of the technology proposed herein.

[0199] The object may alternatively be referred to as a part or a component. The object may be selected from the group consisting of a soft magnetic component of a sensor, inductor, converter, transformer, electric motor, and a generator.

[0200] In the following examples, various ferromagnetic powder compositions according to the first aspect of the technology proposed herein were used to manufacture test objects using the method according to the second aspect of the technology proposed herein. The test objects were compared with test object manufactured from reference composition which differed by not comprising the second type of soft magnetic iron-based core particles. The finished objects, in particular the last produced objects form a manufacturing run, were investigated and compared.

[0201] Generally, the ferromagnetic powder compositions were produced as follows: Step 1 : Soft magnetic iron-based core particles were mixed (10 min) with an aqueous solution of a silicate of the general formula (K2O)a(SiO2)P (potassium silicate, Sibelco Nordic AB, p / a molar ratio of 3.37, solids content 14 wt%) at a concentration (based on dry matter content) of 0.1 wt% to form the first coating on the core particles. The aqueous solution further contained one or more additional compounds or additives of interest as specified for each sample. After the initial mixing, the core particles were dried while being stirred at 60°C for 1 h, followed by further drying without stirring at 120°C.

[0202] The soft magnetic iron-based core particles were a water atomized annealed iron powder having dimensions according to 100 mesh and an apparent density of 3.32 g / cm3 unless otherwise stated.

[0203] Step 2: The mixture from step 1 was mixed with a silane (oligomeric diaminofunctional silane Dynasylan® 1146 from Evonik Industries AG, 1 .5 g in 1 g H2O unless otherwise specified) for 5 min so as to form the second coating, and the resulting mixture was dried at 50°C for 2 h to produce the finished first type of soft magnetic iron-based core particles.

[0204] Steps 1 and 2 were repeated for the second type of soft magnetic iron-based core particles, and the resultant first and second type of soft magnetic iron-based core particles were mixed to produce the ferromagnetic powder composition according to the first aspect of the technology proposed herein for proceeding to step 3, or alternatively only the first type of soft magnetic iron-based core particles was used and proceeded to step 3.

[0205] As an alternative, the first and second type of soft magnetic iron-based core particles were mixed together before step 1 .

[0206] Step 3. A lubricant (0.4 wt% amide wax unless otherwise specified) was added to the ferromagnetic powder composition in order to facilitate producing the test part,

[0207] Generally, the test objects were manufactured as follows:

[0208] The ferromagnetic powder composition was then shaped and compacted (800 MPa with a die temperature of room temperature, 45°C, or 60°C, into test objects (cylinders OD25mmxH20mm).

[0209] The ejection energy given in Joule is a representative value for the 20 mm high test objects.

[0210] Where test objects were heat treated (toroids in Example 2 and Example 4), the heat treatment was performed in three stages in a pre-heated furnace. The three stages comprised a delubrication stage at about 300-400°C during which the compacted part was heated up towards the curing stage, a curing stage at about 350-450°C (first time and temperature given for each sample) in which the coating was cured so as to cause the formation of an electrically insulating bismuth-silicate glass from the first and second coating, and a relaxation stage at 600-700°C (second time and temperature given for each sample) in which the stress from the compaction was released. The oxygen partial pressure during the heat treatment was 15000 ppm (1 .5 wt% oxygen in nitrogen) unless otherwise specified.

[0211] Some parameter measured on the test objects include:

[0212] Electrical resistivity (Res) - how the material resists electric current [p m], Measured using 4-point probe method at 0.001 A with 5 mm distance between measuring points. For Example 2, the parameters were 0.1 A and 10 mm distance.

[0213] Coercivity* (Hc) at 10 kA / m [A / m]

[0214] Maximal permeability* ( i-max) - the maximum value of the ratio between the magnetization that a material obtains in response to an applied magnetic field [unitless].

[0215] Density (d) - density of the test object [g / cm3].

[0216] Magnetic flux density* - induction obtained for a given applied magnetic field [T],

[0217] B4* - magnetic flux density at 4kA / m [T],

[0218] B10* - Magnetic flux density at 10 kA / m [T]

[0219] Total core loss* (at 1T / 1 kHz) - total core loss for a test object obtained for a given induction and frequency [W / kg],

[0220] *For the measurement of magnetic properties, square toroids were wound with 100 drive and 100 sense turns of resin coated copper wire (diameter 0.63 mm) and measured using a Brockhaus MPG 200D. References: IEC 60404-4 (DC measurements) and IEC 60404-6 (AC-measurements).

[0221] TRS - Transverse rupture strength according to SS-EN ISO 3325:2000, on bars with dimensions of 30x12x6 mm [MPa].

[0222] AD - Apparent density according to ISO standard 3923-1 :2018 measured as the ratio between the dry mass and apparent volume of the powder sample [g / cm3].

[0223] FLOW - Hall flow according to SS-EN ISO 4490:2018 [seconds].

[0224] GS - Green strength, measured as TRS but on test parts prior to heat treatment [MPa].

[0225] 5% coated FeSi powder (D5o and better surface finish on Example 1 tested the addition of 5% coated FeSi powder to a ferromagnetic powder otherwise containing coated soft magnetic core particles. The amount of lubricant, as well as the die temperature was varied. For all samples, the compaction pressure was 800 MPa and normal compaction, i.e. where both parts of the die move towards each other over the same stroke length, was used. The component produced was a solid cylinder (GD25 x H20mm) and the last and second to last copy of this component was collected, measured, and photographed. 100 parts were made for each sample unless otherwise specified.

[0226] The results are summarized in table 1 A and 1 B below and photographs of the respective produced part is shown in Figs. 1 A-1 F.

[0227] Table 1 A: Results for density and mean ejection energy

[0228] Table 1 B. Results for AD, Flow and Resistivity measurements

[0229] In conclusion of table 1 and Figs 1A-1G, it can be seen that sample 1 F (5% FeSi, 0.4% lubricant and a preheating of the die to 60°C) provides a very advantageous combination of properties. In particular, sample 1 F, as compared to sample 1 B and 1 D, provides a better surface finish with less or no black residues at a mere 0.02 g / cm3loss of density. The apparent density (AD) of sample 1 F was approximately 3.56 g / cm3resulting in a filling height (pre-compaction) of 38.5 mm as compared to an apparent density of 3.52 g / cm3and a filling height of 42 mm for sample 1 B.

[0230] Fig. 1 H shows that also a lower amount, i.e. 2.5wt% FeSi, provides a similar smoother surface finish as 5 wt% with an even higher density.

[0231] Fig. 11 shows that also a higher amount, i.e. 7.5wt% FeSi, provides a similar smoother surface finish as 5 wt%, however the density is low at 7.35 g / cm3.

[0232] Further, as shown in Fig. 2. the ejection energy for the 100 parts produced according to sample 1 F was higher than for the 1 B reference.

[0233] Accordingly, adding 2.5 to 7.5 wt% FeSi provided a smoother surface finish.

[0234] Example 2: Further results on magnetic properties when including the second type of soft magnetic iron-based core particles.

[0235] Magnetic toroids (OD55 / ID45xH5mm) were manufactured from a reference powder compositions and ferromagnetic powder compositions according to the first aspect of the technology proposed herein, respectively, using a pressure of 800MPa and a die temperature of 100°C. Toroids were heat treated for various times and temperatures and tested as given by tables 2 below: Table 2. Results for magnetic properties

[0236] As seen by table 2, the inclusion of the 5% FeSi does not yield any significant decrease in magnetic and electric properties. Further, as shown by sample 2-2 it can also increase the green strength (GS), or as shown by sample 2-4 and 2-6 it can increase resistivity.

[0237] Example 3: A ferromagnetic powder composition comprising 5% coated FeSi powder (D5Q approximately 30 um) provides a higher ejection energy and better surface finish also for larger compacted parts. Example 1 was repeated using the same core particles and 0.5 wt% amide wax lubricant. Five parts were made from the powder composition with 5% coated FeSi powder, and five parts were made from the powder composition without the 5 wt% coated FeSi powder.

[0238] The results are shown in Figs. 3A and 3B. Fig. 3A shows the test part (OD25xH25mm) obtained when 5% coated FeSi powder was present in the powder composition and the die was at room temperature (left) or preheated to 60°C (right).

[0239] Fig. 3B shows the test part (OD25xH25mm) obtained without 5% coated FeSi powder present in the powder composition and the die was at room temperature (left) or preheated to 60°C (right).

[0240] As seen by comparing Figs 3A and 3B, the inclusion of 5wt% coated FeSi powder provides a smoother, shinier and better surface finish also to these larger (25 mm height vs 20 mm height in Example 1 ) parts. Additionally, the example showed good results for the higher concentration (0.5 wt%) of lubricant.

[0241] The density for the part in Fig. 3A was 7.397 and 7.399 (left, right) and the density of the part in Fig. 3B was 7.399 (both).

[0242] Example 4: Various coating to be used on the first and second types of soft magnetic core particles of ferromagnetic powder composition

[0243] This example shows some different variations of the first and second coatings applied to the first and, optionally also to the second, types of soft magnetic iron-based core particles.

[0244] Details of the coatings and results from measurement on produced test objects (toroids OD55 / ID45xH5mm) are shown in table 4 below.

[0245] Table 4

[0246]

[0247] As seen from the above results, the components of the first and second coatings may be varied widely with good results. Feasible modifications of the technology proposed herein.

[0248] The technology proposed herein is not limited to the embodiments described above and shown in the drawings, which primarily have an illustrative and exemplifying purpose. This patent application is intended to cover all adjustments and variants of the preferred embodiments described herein; thus the present invention is defined by the wording of the appended claims and the equivalents thereof. Thus, the equipment may be modified in all kinds of ways within the scope of the appended claims.

[0249] Throughout this specification and the claims which follows, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or steps or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims

Claims1 . A ferromagnetic powder composition comprising: a) a first type of soft magnetic iron-based core particles, where the surface of each core particle is at least partially covered by an electrically insulating coating which is in direct contact with the surface, and b) a second type of soft magnetic iron-based core particles, wherein the material composition of the first and second types of soft magnetic iron-based core particles is different, wherein the hardness of the second type of soft magnetic iron-based core particles is higher than the hardness of the first type of soft magnetic iron-based core particles, wherein the second type of soft magnetic iron-based core particles makes up 1 to 9 wt%, preferably 2-8 wt%, more preferably 3-7 wt% such as 4-6 wt%, most preferably 5 wt%, of the total amount of the first and second type of soft magnetic iron-based core particles, and wherein at least 80 wt%, more preferably at least 90 wt% such as at least 99 wt%, based on the total weight of the core particles, of the core particles of the first type of soft magnetic iron-based core particles are in the range 45-150 pm as measured according to ISO 4497.

2. The ferromagnetic powder composition according to claim 1 , wherein the hardness of the second type of soft magnetic iron-based core particles, preferably expressed as the Vickers Pyramid Number (HV), preferably HV10, is at least 150%, more preferably at least 250%, most preferably at least 400%, of the hardness of the first type of soft magnetic iron-based core particles.

3. The ferromagnetic powder composition according to any preceding claim, wherein the soft magnetic iron-based core particles of the first type of soft magnetic ironbased core particles consist of iron and inevitable impurities, and wherein the soft magnetic iron-based core particles of the second type soft of magnetic iron-based core particles comprise Fe and at least one alloying element, preferably at least one of Si, Al, P, Ni, and Co.

4. The ferromagnetic powder composition according to any preceding claim, wherein the soft magnetic iron-based core particles of the second type soft of magnetic iron-based core particles comprises, preferably consists of, an alloy of Fe and Si, wherein the alloy of Fe and Si preferably comprises at least 4.5% Si and more preferably at least 6.8% Si.

5. The ferromagnetic powder composition according to any preceding claim, wherein the soft magnetic iron-based core particles of the second type of soft magnetic iron-based core particles have a D50 measured according to SS-ISO 13320-1 which is less than 75 pm, more preferably less than 45 pm, such as 30 pm, and preferably at least 10 pm.

6. The ferromagnetic powder composition according to any preceding claim, wherein the second type of soft magnetic iron-based core particles are gas atomized and / or have an apparent density (AD) of at least 3.7 g / cm3, preferably at least 3.9 g / cm3, and / or are spherical.

7. The ferromagnetic powder composition according to any preceding claim, wherein the first type of soft magnetic iron-based core particles has diameters that are at least 75 pm and at the most 300 pm, preferably at least 75 pm and at the most 180 pm.

8. The ferromagnetic powder composition according to any preceding claim, wherein the electrically insulating coating comprises:(i) a first coating at least partially covering and being in direct contact with the surface of the core particles, the first coating comprising:(1) a silicate of the general formula (K2O)a(SiO2)P, wherein a is moles of K2O, P is moles of SiO2, and the p / a molar ratio is in the interval from 0.5 to 4.1 , (a) wherein the silicate is present in an amount of 0.02 to 1 .0 wt% calculated based on the total weight of the soft magnetic iron-based core particles, and(2) optionally particles of a compound comprising bismuth and oxygen having a D50 measured according to SS-ISO 13320-1 in the interval of 0.1 to 10 pm, wherein the first coating further comprises:(3) nanoparticles having a D50 measured according to ISO 13320-1 of 10-200 nm, or alternatively having a specific surface area (SSA) of 6-120 m2 / g as determined according to ISO 9277:2022, and optionally:(4) a dopant dissolved as an oxo- or hydroxy-anion in the silicate (1 ), and(ii) optionally a second coating at least partially covering the surface of the core particles and / or the first coating, the second coating comprising: a. at least one metal-organic compound having the general formulaR1[(R1)x(R2)y(M)]nOn-lR1(I)orR2[M(OH)2(n+1)](n+1)O(n)R2( II) wherein M is selected from the group consisting of Si, Ti, Al, and Zr; O is oxygen; R1is a hydrolysable group; R2is an organic moiety and wherein at least one R2contains at least one amino group; wherein n is the number of repeating units being an integer between 1 and 20; wherein x is 0 or 1 ; and wherein y is 1 or 2, and x+y is 2, wherein the content of the at least one metal-organic compound is 0.05 to 0.40 wt%, preferably 0.10 to 0.30 wt%, based on the total weight of the soft magnetic iron-based core particles.

9. The ferromagnetic powder composition according to claim 8, wherein the content of nanoparticles in the first coating is 1-30 mol%, preferably 1 -20 mol%, based on the molar content of K (Potassium) in the first coating, and wherein the nanoparticles preferably are selected from the group consisting of Y2O3 nanoparticles, ZrC>2 nanoparticles, ZnO nanoparticles, Mg(OH)2nanoparticles, MgO nanoparticles, CaCOs nanoparticles, AI2O3 nanoparticles, SiC>2 nanoparticles, and TO2 nanoparticles, and wherein the nanoparticles more preferably comprise or consist of Y2O3 nanoparticles.

10. The ferromagnetic powder composition according to any preceding claim, wherein the dopant comprises at least one element from group 5, such as V (Vanadium) or Nb (Niobium), or comprises at least one element from group 6, such as Cr (Chromium), W (tungsten), or Mo (Molybdenum), or comprises Al (Aluminium) or P (Phosphorus), and wherein preferably the content of dopant in the first coating is 1 -30 mol%, preferably 5-20 mol%, more preferably 5-15 mol% or 1-3 mol%, based on the molar content of K (Potassium) in the first coating.11 . The ferromagnetic powder composition according to any preceding claim wherein the surfaces of each soft magnetic iron-based core particle of the second type of soft magnetic iron-based core particles are at least partially covered by an electrically insulating coating which is in direct contact with the surface.

12. The ferromagnetic powder composition according to claim 11 , wherein:a) the electrically insulating coating on the second type of soft magnetic iron-based core particles comprises a first and second coating as defined any of the claims 8- 10, or b) the electrically insulating coating on the second type of soft magnetic iron-based core particles comprises iron phosphate (FePC ).

13. A method of manufacturing an object from the ferromagnetic powder composition according to any of the claims 1-12, comprising the steps of:(i) compacting the ferromagnetic powder composition according to any of the claims 1-12 in a die at a compaction pressure in the range of 300-2000 MPa, preferably 400-1200 MPa, to obtain the object,(ii) ejecting the object from the die, and(iii) optionally heat treating the object in a nonreducing atmosphere, preferably comprising 0-22 wt%, more preferably 0.5 to 2 wt% oxygen (O2) at a temperature in the range of 300-800 °C, preferably 400-750 °C, more preferably 600-700 °C, such as 670-700 °C or 680-700 °C.

14. An object comprising a compacted ferromagnetic powder composition according to any of the claims 1 -12.

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