TECHNICAL FIELD
The present disclosure relates in general to the field of material science and metallurgy. Particularly, but not exclusively, the present disclosure relates to coating of iron powder particles. Further embodiments of the disclosure disclose a method of coating silica on iron powder particles for improving oxidation resistance and flow characteristics.
BACKGROUND OF THE DISCLOSURE
Powder coatings on iron (Fe) powder particles are usually performed to enhance properties of such iron powder particles including, but not limited to, corrosion resistance, electrical resistivity, microwave absorbing properties and the like. In some instances, powder coatings of the iron powder particles may provide environmental protection such as humidity, moisture, salts, dirt, or debris etc. In other instances, the powder coating may be adapted to hermetically seal the iron powder particles from moisture or other environmental conditions and protect iron powder particles from any reactions that occur due to surface reactivity.
For example, it is desirable to protect outer surfaces or to develop hydrophobic surface properties or to improve the shelf life of the iron powder particles, based on desired application in which such iron powder particles are employed.
Further, it is known in the art that presence of oxides in the iron powder particles may result in poor sintering behaviour and restrict oxide from reaching to the full densification in the coated iron powder particles with defined properties. In powder metallurgy, flowability and compressibility of coating on the iron powder particles influences quality of the coated product, where powder flow characteristics helps in easier powder handling which may result in improved filling of the mold during processing which enables in defect-free products. Furthermore, the flowability (i.e., slipperiness of the iron powder) under compaction or external pressure is connected to compressibility of the coated iron powder and is one of the parameters for achieving higher mechanical strength and dimensional accuracy in the products after sintering.
Moreover, insulation between iron powder particles in the final coated iron powder particles is also desired for manufacturing products including, but not limited to, magnetic core. In such case, the iron powder particles are required to be coated with an insulating material. When

insulated, the coated iron powder particles are conventionally known to have poor flowability as compared to the iron powder particles without coating.
Conventionally, there are different techniques known in the art to handle the powder particles preventing from agglomeration and one such technique is addressed in the following document. In patent application JP 2011-213514, it has been documented that silica particles can be dispersed to primary particles in the dispersion medium by selecting an appropriate dispersion medium.
There are different coating techniques conventionally known in the art to protect the powder particles from surrounding environment. In some research papers, it has been documented that dry mechanical coating technique has a potential to enhance the moisture resistance in magnesium powders by coating its surface with carnuba wax [A. Mujumdar et.al, Improvement of humidity resistance of magnesium powder using dry particle coating, Powder Technology 140 (2004) 86–97].
Another document known in the art discloses that there is a possibility to improve the flowability of corn-starch by coating with nano-size silica particles [J. Yang, et.al, Dry particle coating for improving the flowability of cohesive powders, Powder Technology 158 (2005) 21–33].
The present disclosure is directed to overcome one or more limitations stated above or any other limitation associated with the prior arts.
SUMMARY OF THE DISCLOSURE
One or more shortcomings of the prior art are overcome by method as disclosed and additional advantages are provided through the method as described in the present disclosure.
Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure.
In an embodiment, the present disclosure discloses a method for coating silica particles on iron powder particles which results in improvement of oxidation resistance by attaching/bonding

silica particles on surface of the iron powder particles. The present disclosure also aids in quick and simpler way of coating the silica particles on the iron powder particles, which may be suitable for powder metallurgy and other related component manufacturing processes including metal injection moulding (MIM) and additive manufacturing (AM).
In a non-limiting embodiment of the present disclosure, a method for producing iron powder particles with silica coating is disclosed. The method includes steps of mixing iron powder particles and a binder for a first predetermined time to form encapsulated mixture. The encapsulated mixture is then mixed with silica by mechanical mixing process at a predetermined temperature for a second predetermined time to form a coated mixture. The coated mixture is cooled to form coated iron powder particles.
In an embodiment, mixing of iron powder particles and binder is carried out at atmospheric temperature.
In an embodiment, the first predetermined time ranges from 2 minutes to 5 minutes at atmospheric temperature for the encapsulated mixture.
In an embodiment, the second predetermined time ranges from 15 minutes to 35 minutes at elevated temperature from 60ºC to 180 º C for the coated mixture.
In an embodiment, the coated mixture is cooled to room temperature under open atmospheric conditions.
In an embodiment, the average particle size of the iron powder particles is in a range of 5 – 100 µm.
In an embodiment, the carbon content of iron powder particles in wt% ranges from 0.05-0.8, oxygen content of the iron powder is by wt% 0.3-0.8 and total iron content in the iron powder particles is at least 96%.
In an embodiment, the binder in the encapsulated mixture is in the range of 0.001-0.5% (in wt%) based on the average particle size of the iron powder particles.
In an embodiment, the silica is added at a proportion ranging from 0.25 – 2.0% by wt.% to the encapsulated mixture, to form the coated mixture.

In an embodiment, the binder is at least one of wax consisting from a group of carnuba wax, mustard oil, olive oil, and castor oil, which is added in a range of 0.01 – 0.3% by wt.%.
In an embodiment, mechanical mixing process is based on at least one of coating in a double cone, V, W or Y-type blenders or cylindrical-type or Nauta mixer, or hybridizers.
In another non-limiting embodiment of the present disclosure, there is provided coated iron powder particles comprising iron powder particles, comprising carbon composition in the range of 0.02 to 1.0 % (in weight %), oxygen content of the iron powder is by wt% 0.3-0.8 and total iron content to be at least 96%/. The coating has a composition including, by weight percentage (wt%) of, silica 0.25 wt% to 2 wt% and binder 0.001 wt% to 0.5 wt%. The coating is formed by mixing, iron powder particles and a binder for a first predetermined time to form encapsulated mixture. The encapsulated mixture is mixed with silica by mechanical mixing process at a predetermined temperature for a second predetermined time to form a coated mixture, wherein the mixing results in silica being coated using wax or oil-based binders. The coated mixture is cooled to form the coated iron powder particles.
In an embodiment, the average size of iron powder particles ranges from 5-100 µm.
In an embodiment, the total iron content in the iron powder particles is at least 96%.
In an embodiment, the binder is at least one of wax consisting from a group of carnuba wax, mustard oil, olive oil, and castor oil, which is added in a range of 0.01 – 0.3% by wt.%.
In an embodiment, the total silica content in the silica particles is at least 99.8% and the average size of silica particles is in the range of 0.01 µm to 30 µm.
It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined together to form a further embodiment of the disclosure.
The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
The novel features and characteristics of the disclosure are set forth in the appended description. The disclosure itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example only, with reference to the accompanying figures wherein like reference numerals represent like elements and in which:
Figure 1 illustrates an apparatus for coating iron powder particles, according to an exemplary embodiment of the present disclosure.
Figure 2 is a flowchart illustrating a method for producing coated iron powder particles, according to exemplary embodiments of the present disclosure.
Figure 3 illustrates schematic diagram of the method of Figure 2, according to exemplary embodiments of the present disclosure.
Figures 4a and 4b illustrate micrographs of dense close rounded iron powder particles and porous irregular iron powder particles from a scanning electron microscope (SEM), according to exemplary embodiments of the present disclosure.
Figures 5a and 5b illustrate micrographs from a scanning electron microscope (SEM) and a transmission electron microscope (TEM) pertaining to nano-silica particles, in accordance with exemplary embodiments of the present disclosure.
Figures 6a and 6b illustrate images from the scanning electron microscope (SEM) of uncoated iron powder particles and the coated iron powder particles with respective energy dispersive X-ray spectroscopy (EDS) analysis locations, in accordance with exemplary embodiments of the present disclosure.
Figure 7 illustrates field emission scanning electron microscope (FE-SEM) image of silica coated iron powder particle surface with energy dispersive X-ray spectroscopy (EDS) mapping, according to an exemplary embodiment of the present disclosure.

Figure 8 illustrates graph of thermogravimetric analysis (TGA) oxidation studies on uncoated iron powder particles and silica coated iron powder particles, according to exemplary embodiments of the present disclosure.
The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION
The foregoing has broadly outlined the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which form the subject of the description of the disclosure. It should also be realized by those skilled in the art that such equivalent methods do not depart from the scope of the disclosure. The novel features which are believed to be characteristic of the disclosure, as to method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.
In the present document, the word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.
While the disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the spirit and the scope of the disclosure.

The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusions, such that a method that comprises a list of acts does not include only those acts but may include other acts not expressly listed or inherent to such method. In other words, one or more acts in a method proceeded by “comprises… a” does not, without more constraints, preclude the existence of other acts or additional acts in the method.
Embodiments of the present disclosure discloses silica coating on surface of iron powder particles and a method for coating iron powder particles. Coating of iron powder particles improves oxidation resistance, corrosion resistance, flow characteristics, electric resistivity of such iron power particles. The method of present disclosure discloses producing silica coated iron powder particles, with improved insulating and oxidation characteristics. The present disclosure is directed towards producing the silica coated iron powder particles and contaminant free iron powder particles which are widely required in powder metallurgical processing, metal injection molding (MIM) and additive manufacturing (AM) processes.
Henceforth, the present disclosure is explained with the help of figures for a method of producing the coated iron powder particles. However, such exemplary embodiments should not be construed as limitations of the present disclosure since the method may be used for other types of coatings where such need arises. A person skilled in the art may envisage various such embodiments without deviating from scope of the present disclosure.
Figures 1 and 2 are exemplary embodiments of the present disclosure illustrating an apparatus and flowchart depicting method of producing coated iron powder particles. In the present disclosure, corrosion resistance, oxidation resistance, surface characteristics and flow characteristics of the coated iron powder particles may be improved. The method steps described and detailed in view of Figure 2 for producing the coated iron powder particles, and order in which such method steps are described is not intended to be construed as a limitation. Additionally, individual blocks may be deleted from the methods without departing from the scope of the subject matter described herein. The method is particularly applicable to the coated iron powder particles with silica powder, and it may also be extended to other type of powder coatings of iron powder particles as well.
Figure 1 illustrates a mixing apparatus where the iron powder particles, the binder and the silica particles are added to a mixing container (101) of the mixing apparatus. In an embodiment, a mixing apparatus includes base plate (106), hot plate (105), mechanical mixing rod (102),

mixing container (101), top cover (103), blades (104). The mixing container (101) is placed on the hot plate (105) which is rested on a base plate (106). Iron powder particles and binder are introduced into the mixing container (101) and mixed to get the homogeneous binder encapsulated mixture. In an embodiment, mixing can be performed by either hand or with the help of mechanical mixing rod (102). The mechanical mixing rod (102) consists of blades (104) attached to the rod and the blades (104) ensures uniform mixing of the iron powder particles and the binder. Mixing container consists of a top cover (103) which conceals the mixing container (101) and allows the mechanical mixing rod (102) through the top cover (103). Further, the silica particles are added to the binder encapsulated mixture and then the hot plate (105) is operated at elevated temperature and the mixing continuous for a predefined time to form the silica coated iron powder particles. In an embodiment, the mixing container (101) placed above the hot plate (105) which is unidirectional, and the uniform heating of the mixture takes place radially.
As shown in Figure 2, the block 201 includes mixing of the iron powder particles and the binder for a first predetermined time to form an encapsulated mixture. It is to be understood that the term “encapsulate” may refer to coating forming a thin cover of the binder on an outer surface of the iron powder particles, where such coating may cover substantial portion of the iron powder particles. For example, such covering of the binder on the iron powder particles may range from at least 51% of the outer surface of the iron powder particles. In an embodiment, the iron powder particles are in the form of reduced or atomized and are highly pure in nature as the total iron content is greater than 98%. Further, the iron powder particles are either dense close rounded in morphology (as shown in figure 4a) or porous irregular in nature (as shown in figure 4b). In an embodiment, the carbon content of iron powder particles ranges from 0.05 wt% - 0.8 wt% and the total oxygen content in the iron powder particles ranges from 0.3 wt% to 0.8 wt%. Further, the average size of the iron powder particles ranges from 5 - 100 µm.
In an embodiment, the binder is configured to impart adhesion between the iron powder particles under wet conditions, thereby increasing binding ability, plasticity and compactibility. The binder may be at least one of wax or oil-based binders, which help in binding and coating particles on the iron powder particles. In an embodiment, the binder may be carnuba wax which may be used to bind the coated particles on the surface of iron powder particles. In an embodiment, the waxes are able to liquify in the range of 80°C -100°C and may be smeary and slow drying in nature. In an embodiment, other binders employable for coating as per the

present disclosure may extend to include plant-based binders in the form of oil such as, but not limited to, castor oil, olive oil, mustard oil, almond oil, or mineral oils including, but not limited to, silicone oil and the like.
In an embodiment, the binder composition is chosen such that the binder includes properties which are able to impart durability and may be easy to apply. In the present disclosure, the binder may be employed in the range of 0.001 wt% - 0.5 wt% and amount of the binder to be used depends on various factors such as size, surface roughness, specific surface area, morphology and particle size distribution of coating particles and iron powder particles. In an embodiment, the binder is added in a range of 0.01 - 0.3% by wt.% to the iron powder particles.
As shown in the step 201 of Figure 3, the mechanical mixing of iron powder particles and the binder in a mixing container (shown in Figure 1) at first predetermined time forms homogenised binder encapsulated mixture. In an embodiment, mixing the iron powder particles with the binder increases glueyness characteristics of the surface of the iron powder particles. In an embodiment, the first predetermined time ranges from 2 minutes to 5 minutes and mixing of the iron powder particles and the binder takes place under atmospheric temperature.
In an embodiment, the mixing process takes place in at least one of double cone, V, W or Y-type blenders or cylindrical-type blender or Nauta mixer, or hybridizers.
Now referring to block 202, the silica particles are added to the encapsulated mixture and mixed at a predetermined temperature for second predetermined time. In an embodiment, the predetermined temperature ranges from 60℃ to 180℃ and the predetermined time ranges from 15 minutes to 35 minutes.
In the present disclosure, the silica particles are in amorphous form and are used for coating on the surface of the encapsulated mixture. In an embodiment, the average silica particle size ranging from 0.01 µm to 30 µm and the bulk density of silica particles ranges around 400 g/L or less. In an embodiment, the purity of silica particles is greater than 99.8%.
In an embodiment, the mixture quantity in the mixing chamber not to be exceeded greater than one-half of the capacity of the mixing chamber. Further, size difference between the iron powders and silica particles having more than seven times to enable better surface coating properties on each powder particle.

In an embodiment, the silica particles are added to the mixture depending on coating thickness and final silica composition desired in the coated iron powder particles. Further, higher percentage of silica addition results in a risk of silica segregation in the mixture and the silica particles may remain unbonded with the iron powder particles. However, with lower percentage addition of the silica particles, there may not be enough silica available to have an effective surface coating on the iron powder particles. The silica particles are added in the range of 0.25- 2.0% (in wt.%) depending on the particle size, morphology, character of the host particles, and the coating process is designed based on the desired coating thickness and surface coverage requirement on the iron powder particles.
As shown in step 202 of figure 3, the silica particles are added to the encapsulated mixture and such mixture is either manually or mechanically mixed at a temperature range of 60℃ to 180℃ for 15 minutes to 35 minutes. With the hot mechanical mixing step, the silica particles are attached to the encapsulated mixture. Further, with progressive hot mechanical mixing results in entire mixture being non-sticky and coated with the silica particles due to combination of shear mixing and internal shear forces between the iron powder particles and the silica particles.
As per block 203, the coated mixture is cooled to form the coated iron powder particles, where the encapsulated mixture is coated by the silica particles. In an embodiment, the coated iron powder particles are allowed to cool down to room temperature under open atmospheric conditions. Further, mixing step is performed till temperature reaches below 45℃ to avoid overheating or localized heating of the iron powder particles. In an embodiment, mixing of the coated iron powder particles may be performed till temperature reaches room temperature.

Example:
Powder Raw Material Method of production Morphology
A Pure Iron powder (Dense) Atomization/Reduction Irregular, rounded
B Pure Iron powder (Porous) Hydrogen Reduction Irregular, porous
T able 1

As evident from the Table 1, the iron powder particles to be coated are either dense rounded or porous irregular in morphology. Further, the iron powder particles are produced by either atomization or by reduction method.
As shown in Figure 4a, the SEM micrograph shows that the iron powder particles having dense close rounded morphology and in Figure 4b, the SEM micrograph shows that the iron powder particles are porous and irregular in morphology.
In an embodiment, Figure 5a and 5b shows the SEM and TEM micrographs of silica particles indicating the fine sized particles which are used for coating iron powder particles.

Physical Properties Improvement (%)
Apparent Density (g/cm3) 15-20
Tap Density (g/cm3) 3-5
Angle of Repose(degrees) 15-181
Specific surface area (BET) (m2/g) 14-16
Flowability (s-1) 12-15
Contact angle with water drop (degrees) 20-22
Tabl e 2
The improvement in physical properties of silica coated iron powder particles is disclosed in Table 2. From the above Table 2, hydrophobic characteristics improvement in the contact angle with water drop to an extent of 20 - 22 percentage improvement of the coated iron powder as compared to uncoated powder.

Spectrum Oxygen Silicon Iron
C12 411 2.20 0.28 97.50

C4 395 55.04 39.97 4.98
Table 3
Figure 6a and 6b shows the scanning electron microscope (SEM) image of uncoated iron powder particles and silica coated iron powder particles with respective energy dispersive spectroscopy (EDS) locations. As evident from the Figure 6a and 6b, the electron microscopy shows a clear distinct difference between the uncoated and silica coated iron powder particles surface texture. The uncoated surface texture at high magnification looks smoother in nature while after silica coating, the coated surface appears fluffy and powdery in nature due to silica adhesion on the surface of the iron powder particles as shown in Figure 6(b).
The above Table 3 shows the results of Energy dispersive spectroscopy (EDS) point analysis at locations indicated in Figure 6a and 6b. Further, EDS examination obtained on the surface of the uncoated and coated iron powder particles shows clear compositional differences as seen in Table 3.
In an embodiment, SEM mapping of the coated iron powder particles revealed that amorphous silica particles are in nano scale regime as shown in Figure 7. As evident from the figure 8, thermogravimetric oxidation studies (TGA) reveals that the onset of oxidation of uncoated iron powder particles is close to 380°C and after silica coating, the onset of oxidation shifted to higher temperature close to 640°C . Therefore, the silica coating on iron powder particles has resulted in improvement in oxidation characteristics. Further, with relative increase in binder percentage in the coating mixture, the oxidation resistance of the silica coated iron particles has subtly improved further as seen in Figure 8.
In an embodiment, TGA studies reveals that the sharp initial weight loss around 280°C on heating attributed to the decomposition temperature of the binder constituent.
Thus, it is clear from the physical properties, that the target properties cannot be achieved when the processing is not done as per the present disclosure.
In an embodiment of the present disclosure, the silica coated iron powder particles of the present disclosure may be used any application including but not limiting to powder

metallurgical processing to MIM and AM manufacturing techniques and the like. Silica coated iron powder particles may be used in any other industrial manufacturing application.
Equivalents:
With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.
It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is

used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."
While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Referral Numerals:
Referral Numerals Description
101 Mixing container
102 Mechanical mixing rod
103 Top cover
104 Blade
105 Hot plate
106 Base plate
107 Mixture of iron powder particles, binder and silica particles
201-203 Flowchart blocks
201 Mixing stage
202 Hot mechanical mixing stage
203 Cooling stage

We Claim:
1. A method for coating iron powder particles, the method comprising:
mixing, iron powder particles and a binder for a first predetermined time to form encapsulated mixture;
mixing, the encapsulated mixture with silica by mechanical mixing process at a predetermined temperature for a second predetermined time to form a coated mixture, wherein the mixing results in silica being coated on the encapsulated mixture; and
cooling, the coated mixture to form the coated iron powder particles.
2. The method as claimed in claim 1, wherein the mixing of iron powder particles and the binder is carried out at atmospheric temperature.
3. The method as claimed in claim 1, wherein the first predetermined time ranges from 2 minutes to 5 minutes.
4. The method as claimed in claim 1, wherein the predetermined temperature ranges from 60°C to 180°C .
5. The method as claimed in claim 1, wherein the second predetermined time ranges from 15 minutes to 35 minutes.
6. The method as claimed in claim 1, wherein the coated mixture is cooled to a room temperature, under open atmospheric conditions.
7. The method as claimed in claim 1, wherein average particle size of the iron powder particles is in a range of 5-100 µm.
8. The method as claimed in claim 1, wherein carbon content of the iron powder particles in wt% ranges from 0.05-0.8, oxygen content of the iron powder is by wt% 0.3-0.8 and total iron content in the iron powder is at least 96%.
9. The method as claimed in claim 1, wherein the binder in the encapsulated mixture is in the range of 0.001-0.5% (in wt%) based on the average particle size of the iron powder particles.

10. The method as claimed in claim 1, wherein the silica is added at a proportion ranging from 0.25 – 2.0% by wt.% to the encapsulated mixture, to form the coated mixture.
11. The method as claimed in claim 1, wherein the binder is at least one of wax, carnuba wax, mustard oil, olive oil, which is added in a range of 0.01 – 0.3% by wt.%.
12. The method as claimed in claim 1, wherein mechanical mixing process is based on at least one of coating in a double cone, V, W or Y-type blenders or cylindrical-type blender or Nauta mixer, or hybridizers.
13. Coated iron powder particles, comprising:
iron powder particles comprising carbon composition in the range of 0.02 to 1.0 % (in weight %), oxygen content of the iron powder is by wt% 0.3-0.8 and total iron content to be at least 96%; and
a coating, having a composition comprising, by weight percentage (wt%) of:
silica 0.25 wt% to 2 wt%; binder 0.001 wt% to 0.5 wt%; wherein, the coating is formed by mixing, iron powder particles and a binder for a first predetermined time to form encapsulated mixture;
mixing, the encapsulated mixture with silica by mechanical mixing process at a predetermined temperature for a second predetermined time to form a coated mixture, wherein the mixing results in silica being coated using wax or oil-based binders; and cooling the coated mixture to form the coated iron powder particles.
14. The coated iron powder particles as claimed in claim 13, wherein the average size of iron powder particles ranges from 5-100 µm.
15. The coated iron powder particles as claimed in claim 13, wherein the total iron content in the iron powder particles is at least 96%.
16. The coated iron powder particles as claimed in claim 13, wherein the binder is at least one of wax, such as carnuba wax, and any one of oil based binders such as mustard oil, olive oil, castor oil, which is added in a range of 0.01 – 0.3% by wt.%.

17. The coated iron powder particles as claimed in claim 13, wherein the total silica content in the silica particles is at least 99.8%.
18. The coated iron powder particles as claimed in claim 13, wherein the average size of silica particles is in the range of 0.01 µm to 30 µm.