Claims:We claim:

1. A method for depositing hydrophobic metallic coating on a substrate (S), the method comprising:
generating plasma plumes (3) in a plasma spray system (10);
supplying inert gas encompassing the plasma plumes (3); and
feeding an iron-based alloy powder into a stream of the plasma plumes (3) and directing the stream of plasma plumes onto a surface of the substrate (S) to be coated, thereby developing the layer of hydrophobic coating on the surface of the substrate (S).

2. The method as claimed in claim 1, wherein the iron-based alloy powder is a high phosphorus pig iron obtained from a metallurgical furnace.

3. The method as claimed in claim 2, wherein the high phosphorus pig iron obtained from a metallurgical furnace is melted and processed through a water atomization process to obtain a high phosphorus pig iron powder.

4. The method as claimed in claim 2, wherein the high phosphorus pig iron powder comprises composition in weight percentage [wt%] of: 3.5 wt% carbon, 1.4 wt% phosphorus, 2.0 wt% Silicon, 0.5 wt% manganese, 0.030 wt% sulfur and 92.6 wt% iron.

5. The method as claimed in claim 2, wherein the high phosphorus pig iron powder comprises atom composition of 14.04 at% of carbon, 2.18 at% phosphorus, 3.43 at% silicon, 0.44 at% manganese and 79.91 at% iron.

6. The method as claimed in claim 1, wherein the plasma plume (3) is generated by supplying plasma forming gas around an electrical arc developed between an anode and a cathode within a plasma gun (1) of the plasma spray system (10).

7. The method as claimed in claim 1, wherein the plasma plume (3) melts the iron-based alloy powder, melted, iron-based alloy powder is sprayed on to the surface of the substrate (S).

8. The method as claimed in claim 1, wherein the inert gas reduces the temperature of the plasma plumes (3).

9. The method as claimed in claim 1, wherein the iron-based alloy powder is fed into the stream of plasma plumes (3) through a feeding unit (4).

10. The method as claimed in claim 1, wherein particle size of the iron-based alloy powder fed into the stream of plasma plumes (3) is of varying sizes including small particles, medium particles and large particles, such that the small particles melt uniformly, and the medium and large particles melt non-uniformly.

11. The method as claimed in claims 7 and 10, wherein the melted iron-based alloy powder sprayed on to the surface of the substrate (S) forms micropillars of pre-defined dimensions on the surface of the substrate (S).

12. The method as claimed in claim 11, wherein the pre-defined dimension of the micropillars range from 5 microns to 10 microns.

13. The method as claimed in claim 6, wherein the plasma forming gas is at least one of nitrogen (N2), argon (Ar) and hydrogen (H2).

14. The method as claimed in claim 11, wherein nitrogen gas flow rate ranges from 100-120 SCFH and hydrogen gas flow rate ranges from 5-15 SCFH.

15. The method as claimed in claim 1, wherein the feed rate of the high phosphorus pig iron power to the plasma plume ranges from 7-10 grams per minute.

16. The method as claimed in claim 1, wherein inert gas is at least one of argon and helium.

17. The method as claimed in claim 1, wherein the inert gas is supplied at a rate ranging from 8 to 12 SCFH.

18. The method as claimed in claim 1, wherein the traverse speed of the plasma spray system (10) ranges from 520 rpm to 560 rpm.

19. The method as claimed in claim 1, wherein the electrical arc is generated by supplying electrical power ranging from 15 to 25kW.

20. A plasma spray system (10) for depositing hydrophobic coating on a substrate (S), the system comprising:
a plasma gun (1) defining a housing to accommodate an anode and a cathode, wherein a passageway is defined within the plasma gun (1) to receive plasma forming gas, wherein the plasma forming gas is supplied around an electrical arc generated by striking of the anode and a cathode to generate plasma plumes (3);
an inert shroud (2) structured to encompass the plasma gun (1), wherein the inert shroud (2) is configured to supply inert gas encompassing the plasma plumes (3); and
a feeding unit (4) positioned at an exit of the plasma gun (1), the feeding unit (4) is structured to feed iron-based alloy powder into a stream of the plasma plumes (3), wherein the stream of plasma plumes is directed onto a surface of the substrate (S) to be coated, thereby developing the layer of hydrophobic coating on the surface of the substrate (S).

21. The system (10) as claimed in claim 20, wherein the iron-based alloy powder is a high phosphorus pig iron obtained from a metallurgical furnace, the high phosphorus pig iron obtained from a metallurgical furnace is melted and processed through a water atomization process to obtain in a high phosphorus pig iron powder.

22. The system (10) as claimed in claim 20, wherein the electrical arc between the cathode and anode is generated by supplying electrical power ranging from 15 to 25kW.

23. The system (10) as claimed in claim 20, wherein the traverse speed of the plasma spray system (10) ranges from 520 rpm to 560 rpm.

24. The system (10) as claimed in claim 20, wherein the plasma plume (3) melts the iron-based alloy powder, vaporized iron-based alloy powder is sprayed on to the surface of the substrate (S).

25. The system (10) as claimed in claim 20, wherein particle size of the iron-based alloy powder fed into the stream of plasma plumes (3) is of varying sizes including small particles, medium particles and large particles, such that the small particles melt uniformly, and the medium and large particles melt non-uniformly.

26. The system (10) as claimed in claim 24 and 25, wherein the vaporized iron-based alloy powder sprayed on to the surface of the substrate (S) forms micropillars of pre-defined dimension on the surface of the substrate (S).

27. The system (10) as claimed in claim 20, wherein the inert gas is at least one of argon and helium.

Dated 31st day of March 2021

GOPINATH A S
IN/PA 1852
OF K&S PARTNERS
AGENT FOR THE APPLICANT
, Description:FORM 2
THE PATENTS ACT, 1970
[39 of 1970]
&
THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
[See Section 10 and Rule 13]

TITLE: “A METHOD FOR DEPOSITING HYDROPHOBIC METALLIC COATING ON A SUBSTRATE”

Name and Address of the Applicant:

1. TATA STEEL LIMITED, Jamshedpur, Jharkhand, India 831001.
2. Indian Institute of Technology Patna, Bihta, Patna-801106 (Bihar), India

Nationality: INDIAN

The following specification particularly describes the nature of the invention and the manner in which it is to be performed
TECHNICAL FIELD:
Present disclosure relates in general to a field of surface coatings. Particularly, but not exclusively, the present disclosure relates a method for developing hydrophobic coatings on the surface of a substrate. Further embodiments of the present disclosure disclose a system and method for developing metal based hydrophobic coatings on metallic substrates.

BACKGROUND OF THE DISCLOSURE:

Hydrophobic coatings are becoming increasingly popular in numerous applications, such as for example windows, TV screens, DVD disks, cooking utensils, clothing, medical instruments etc., because they are easy to clean and have low adhesive properties. Generally, a hydrophobic material or coating is characterized by a static contact angle of water (θ) of 90° or above. Hydrophobic polymeric materials such as poly(tetrafluoroethene) (PTFE) or polypropylene (PP) have been available for decades. These materials suffer from a limited hydrophobicity, as well as inferior mechanical properties as compared to engineering materials or highly crosslinked coatings. For instance, PP has a static contact angle of water of roughly 100° whereas PTFE, which is amongst the most hydrophobic polymeric material known, has a static contact angle of water of roughly 100°.

Some hydrophobic coatings are being referred to in the art as super-hydrophobic coatings are generally defined by a static water contact angle above 140°.
Surfaces with super-hydrophobic properties are found in nature, for example the lotus leaf or cabbage leaf. The waxes secreted onto the leaf's rough surface reduce the adhesion of water and contaminating particles to the leaf. Water droplets deposited on the leaf simply roll off, gathering dirt particles and cleaning the leaf in the process.

Hydrophobic coatings are generally prepared from the polymeric materials [as iterated above] which lacks the robustness and longevity. Moreover, due to low thermal stability and inferior mechanical properties such as wear and abrasion, polymer-based coatings are not considered in many of the industrial applications. Hence, there is a need for the development of a robust, economical hydrophobic coatings free from the drawbacks of polymer-based materials. The development of robust hydrophobic coatings by modification in the surface energy and surface morphology is a promising approach. It is also desirable to develop these coatings through a simple, economical, scalable and industry viable method.

One of the patent publications US20060246297A1 disclose plasma spray process for structuring self-cleaning glass surfaces and self-cleaning glass surfaces. Molten or heat softened particles of inorganic material are plasma spray deposited onto the surface of a substrate to create a micro-rough surface. If desired, a hydrophobic top coating layer can optionally be applied to the micro-rough surface. The micro-structured surface formed according to the invention is durable and self-cleaning.

The present disclosure is directed to overcome one or more limitations stated above or any other limitations associated with the conventional arts.

The information disclosed in this background of the disclosure section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

SUMMARY OF THE DISCLOSURE

One or more shortcomings of the conventional arts are overcome by a system and a method as claimed and additional advantages are provided through the provision of system and the method as claimed 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 one non-limiting embodiment of the disclosure, a method for depositing hydrophobic metallic coating on a substrate is disclosed. The method includes generating plasma plumes in a plasma spray system. Further, inert gas is supplied, wherein the inert gas encompasses the plasma plumes. The method further includes feeding of iron-based alloy powder into a stream of the plasma plumes and directing the stream of plasma plumes onto a surface of the substrate to be coated, thereby developing the layer of hydrophobic coating on the surface of the substrate.

In an embodiment of the disclosure, the iron-based alloy powder is a high phosphorus pig iron obtained from a metallurgical furnace.

In an embodiment of the disclosure, the high phosphorous pig iron obtained from a metallurgical furnace is melted and processed through a water atomisation process to obtain a high phosphorus pig iron powder.

In an embodiment of the disclosure, the high phosphorus pig iron powder comprises composition in weight percentage [wt%] of: 3.5 wt% carbon, 1.4 wt% phosphorus, 2.0 wt% Silicon, 0.5 wt% manganese, 0.030 wt% sulfur and 92.6 wt% iron. Further, the high phosphorus pig iron powder comprises atom composition of 14.04 at% of carbon, 2.18 at% phosphorus, 3.43 at% silicon, 0.44 at% manganese and 79.91 at% iron.

In an embodiment of the disclosure, the plasma plume is generated by supplying plasma forming gas around an electrical arc developed between an anode and a cathode within a plasma gun of the plasma spray system. The plasma forming gas is at least one of nitrogen (N2), argon (Ar) and hydrogen (H2). The nitrogen gas flow rate ranges from 100-120 SCFH and hydrogen gas flow rate ranges from 5-15 SCFH.

In an embodiment of the disclosure, the plasma plume melts the iron-based alloy powder, melted, iron-based alloy powder is sprayed on to the surface of the substrate.

In an embodiment of the disclosure, the inert gas reduces the temperature of the plasma plumes.

In an embodiment of the disclosure, the iron-based alloy powder is fed into the stream of plasma plumes through a feeding unit.

In an embodiment of the disclosure, particle size of the iron-based alloy powder fed into the stream of plasma plumes is of varying sizes including small particles, medium particles and large particles, such that the small particles melt uniformly, and the medium and large particles melt non-uniformly.

In an embodiment of the disclosure, the vaporized iron-based alloy powder sprayed on to the surface of the substrate forms micropillars of pre-defined dimensions on the surface of the substrate. The pre-defined dimension of the micropillars range from 5 microns to 10 microns.

In an embodiment of the disclosure, the feed rate of the high phosphorus pig iron power to the plasma plume ranges from 7-10 grams per minute.

In an embodiment of the disclosure, inert gas is at least one of argon and helium. The inert gas is supplied at a rate ranging from 8 to 12 SCFH.

In an embodiment of the disclosure, the traverse speed of the plasma spray system ranges from 520rpm to 560rpm.

In an embodiment of the disclosure, the electrical arc is generated by supplying electrical power ranging from 15 to 25kW.

In another non-limiting embodiment, a plasma spray system for depositing hydrophobic coating on a substrate is disclosed. The system includes a plasma gun defining a housing to accommodate an anode and a cathode. The plasma gun defines a passageway to receive plasma forming gas. The plasma forming gas is supplied around an electrical arc generated by striking of the anode and the cathode to generate plasma arc. The system further includes an inert shroud structured to encompass the plasma gun. The inert shroud is configured to supply inert gas encompassing the plasma plumes. A feeding unit is positioned at an exit of the plasma gun. The feeding unit is structured to feed iron-based alloy powder into a stream of the plasma plumes. The stream of plasma plumes is directed onto a surface of the substrate to be coated, thereby developing the layer of hydrophobic coating on the surface of the substrate.

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 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 characteristic of the disclosure are set forth in the appended claims. 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:

FIG.1 illustrates an exemplary schematic view of a system for depositing hydrophobic metallic coating on a substrate, in accordance with an embodiment of the present disclosure.

FIG.2 is a flow diagram of a method for depositing hydrophobic metallic coating on a substrate, in accordance with an embodiment of the present disclosure.

FIG.3 is a scanning electron microscopic image of the hydrophobic coating deposited on a substrate, in accordance with an embodiment of the present disclosure.

FIG.4 (A and B) illustrate a contact angle of the developed hydrophobic coating and image of the water droplets over the hydrophobic coating depicting hydrophobic nature of substrate, in accordance with an embodiment 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 structures and 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 claims of the disclosure. It should be appreciated by those skilled in the art that the conception and specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent processes do not depart from the spirit and scope of the disclosure as set forth in the appended claims. The novel features which are believed to be characteristic of the disclosure, both as to its organization and 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. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.

Embodiments of the present disclosure discloses a system and a method for depositing hydrophobic metallic coating on a substrate. The hydrophobic coating developed by the method of the present disclosure ensures a robust metallic hydrophobic coating on the substrate via a single step industrially viable thermal process. The hydrophobic coating developed in the present disclosure may withstand significantly higher temperatures. Also, the mechanical wear and abrasion of the hydrophobic coating may be improved significantly over the conventional polymer based hydrophobic coatings.

The system for depositing the hydrophobic coating may be a plasma spray system. In an embodiment, the hydrophobic coating may be deposited on the substrate made of steel but not limiting to the same. The plasma spray system of the present disclosure may include a plasma gun. The plasma gun may define a housing and may be structured to accommodate an anode and a cathode. Further, the plasma gun may be defined with a passageway. The passageway may be configured to receive plasma forming gas. The plasma forming gas may be supplied from a source to the plasma gun. The plasma forming gas may be supplied around an electrical arc generated by striking of the anode and the cathode to generate plasma plumes. The system further includes an inert shroud structured to encompass the plasma gun. The inert shroud may be configured to supply inert gas encompassing the plasma plumes.

A feeding unit may be positioned at an exit of the plasma gun. The feeding unit may be structured to feed iron-based alloy powder into a stream of the plasma plumes. The stream of plasma plumes may be directed on to a surface of the substrate to be coated, thereby developing the layer of hydrophobic coating on the surface of the substrate. Hereinafter, the method for developing hydrophobic metallic coating is described.

The method of depositing the hydrophobic coating includes generating plasma plumes in the plasma spray system. As iterated above, the plasma plumes may be generated by supplying plasma forming gas around the electrical arc developed between the anode and cathode. The system further includes supplying the inert gas encompassing the plasma plumes. Further, the iron-based alloy powder may be fed into a stream of plasma plumes through the feeding unit. The iron-based alloy powder may be made of high phosphorous pig iron obtained from metallurgical furnace. The high phosphorus pig iron may be obtained from a metallurgical furnace may be melted and processed through a water atomization process to obtain the high phosphorus pig iron powder. In an embodiment, composition in weight percentage of the high phosphorus pig iron may be 3.5 wt% carbon, 1.4 wt% phosphorus, 2.0 wt% silicon, 0.5 wt% manganese, 0.030 wt% sulfur and 92.6 wt% iron. In an embodiment, particle size of the iron-based powder fed into the stream of plasma plumes may be of varying sizes including small particles, medium particles, and large particles, such that the small particles melt uniformly, and the medium and large particles melt non-uniformly. The plasma plume may melt the iron-based alloy, in this case high phosphorus pig iron, the iron-based alloy powder may melt the powder. The melted powder may be sprayed on to the surface of the substrate. Once sprayed onto the substrate, the melted iron-based alloy powder forms micro-pillars of pre-defined dimensions. In an embodiment, the inert gas supplied encompassing the plasma plumes may reduce the temperature of the plasma plumes and aid in uneven melting of the iron-based alloy powder. Thus, leading to formation of micropillars on the substrate. A layer of hydrophobic coating is developed due to the formation of micropillars.

The terms “comprises…. a”, “comprising”, or any other variations thereof used in the specification, are intended to cover a non-exclusive inclusions, such that an assembly that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or method. In other words, one or more elements in an assembly proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the assembly.

Henceforth, the present disclosure is explained with the help of one or more figures of exemplary embodiments. However, such exemplary embodiments should not be construed as limitation of the present disclosure.

The following paragraphs describe the present disclosure with reference to FIG(s) 1 to 4. In the figures, the same element or elements which have similar functions are indicated by the same reference signs. For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to specific embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated methods, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention pertains.

The following detailed description is merely exemplary in nature and is not intended to limit application and uses. Furthermore, there is no intention to be bound by any theory presented in the preceding background or summary or the following detailed description. It is to be understood that the disclosure may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices or components illustrated in the attached drawings and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions or other physical characteristics relating to the embodiments that may be disclosed are not to be considered as limiting, unless the claims expressly state otherwise. Hereinafter, preferred embodiments of the present disclosure will be described referring to the accompanying drawings. While some specific terms directed to a specific direction will be used, the purpose of usage of these terms or words is merely to facilitate understanding of the present invention referring to the drawings. Accordingly, it should be noted that the meanings of these terms or words should not improperly limit the technical scope of the present invention.

Embodiments of the disclosure are directed to a process for coating a substrate (S) with a hydrophobic coating. In one embodiment, the substrate (S) may be roughened, and then coated with the hydrophobic coating. Parameters for the roughening and the coating may be optimized to maximize an adhesion strength of the hydrophobic coating to the substrate (S), and thus to reduce delamination of the hydrophobic coating from the substrate (S). Optimization of a plasma spray process may include optimization of a plasma power i.e., plasma plumes (byproduct of voltage and current), a primary and secondary gas flow rate, powder size and a powder material composition and/or powder feed rate. Other optimized parameters may include a gun distance, a gun moving speed, a gun moving pitch, and so on.

The hydrophobic coating on the substrate (S) may be highly resistant to plasma etching, and the substrate (S) may have superior mechanical properties such as wear and abrasion resistance. Performance properties of the coated hydrophobic substrate may include a relatively high thermal capability, a relatively long lifespan.

As an initial matter it should be noted that the term “gun” may be used in the coating industry to describe an elongated, flexible harness called the “cable” comprising an isolation tube with a rear end connectable to a power supply system of the type including a power source. The front end of the “gun” has a torch to perform the desired operation. The term “gun” is often used to mean either the spraying/coating head or the whole unit. In some instances, the term “gun” may be used herein to describe the coating head. In any event, the context of which the terms are used herein will sufficiently explain how the terms are used.

With reference to FIG.1, a schematic drawing of a thermal spraying system is shown. In the thermal spraying process, a powder material is continuously fed into the heat source, wherein the powder material may be in a partially molten state. In the thermal spraying system, heat source may be from plasma or arc. The thermal spraying system (10) also referred to as plasma spray system (10) [hereinafter the thermal spraying system and the plasma spray system may be used interchangeably] may include a plasma generator or gun head, referred to as plasma gun (1). The plasma gun (1) may be defined with a nozzle including a nozzle orifice. Within the plasma gun (1), an electrically conductive wire may be positioned as anode and a cathode. In an embodiment, both the anode and the cathode may be suitably insulated from the nozzle and the body of the plasma gun (1). The anode and cathode may be insulated using suitable insulating materials. Electric power may be applied by a power source in form of a direct current, where positive potential may be connected to the cathode and the negative potential may be connected to the anode [cathode and anode are hereinafter referred to as an electrode]. In an embodiment, the plasma gun (1) may be defined with a passageway [not shown]. The passageway may be configured to channelize plasma forming gas, provided by plasma gas source around the electrode. In an embodiment, the plasma forming gas may be a mixture of nitrogen (N2) and hydrogen (H2). However, the plasma forming gas iterated above should not be construed as a limitation of the present disclosure as any gas which is capable of generating plasma may be used in the present disclosure.

Further, the system (10) includes an inert gas shroud (2) defined around the plasma gun (1). The inert gas shroud (2) may be designed to supply inert gas surrounding plasma plumes that may be generated in the plasma gun (1) [the process of generating plasma plumes will be set forth hereinafter in the present disclosure]. The inert gas used may be at least one of argon, helium, and the like. The system (10) further includes a feeding unit (4). The feeding unit (4) may be positioned at an exit of the plasma gun (1). The feeding unit (4) may be defined with an inlet and an outlet. The inlet of the feeding unit (4) may be connected to a powder material source and outlet may be disposed at a proximal distance to the nozzle of the plasma gun (1). The powder-based material used in the present disclosure may be an iron-based alloy powder. In an embodiment, the iron-based alloy powder may be high phosphorous pig iron. The high phosphorus pig iron may be obtained from a metallurgical furnace. The high phosphorus pig iron [HPPI] obtained from the metallurgical furnace may be melted and process through a water atomization process to obtain a HPPI powder. The composition of the HPPI powder of the present disclosure is set forth below.

The HPPI powder include composition in weight percentage [wt.%] of 3.5 wt.% carbon, 1.4 wt.% phosphorous, 2.0 wt.% silicon, 0.5 wt.% manganese, 0.030 wt.% sulfur and 92.6 wt.% iron. In other terms, the HPPI powder includes atom composition of 14.04 at% of carbon, 2.18 at% of phosphorous, 3.43 at% silicon, 0.44 at% manganese and 79.91 at% iron. The iron-based alloy powder, in this case the HPPI powder, fed into the plasma plumes (3) may be processed into wide size distribution. For instance, the iron-based alloy powder fed into the stream of the plasma plumes (3) may be of varying sizes including small particles, medium particles, and large particles. In an embodiment, the size of small particles ranges from 20- 35-micron, medium particles range from 35- 65 micron, and large particles range from greater than 65 micron. The method for depositing the hydrophobic metallic coating on the substrate (S) may be elucidated hereinafter with the aid of FIG.2. In an embodiment, the substrate (S) in the present disclosure may be a steel substrate but not limiting to the same.

FIG.2 is an exemplary embodiment of the present disclosure, illustrating a flowchart of the method for depositing hydrophobic metallic coating on the substrate (S).

As illustrated in FIG.2, the method comprises one or more blocks illustrating the method for depositing hydrophobic metallic coating on the substrate (S).

The order in which the method is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method. Additionally, individual blocks may be deleted from the methods without departing from the spirit and scope of the subject matter described herein. Furthermore, the method can be implemented in any suitable hardware, software, firmware, or combination thereof.

Now referring to FIG.2 in conjunction with FIG.1, the plasma gun (1) may be configured to receive plasma forming gas from the plasma forming gas source. In an embodiment, the plasma forming gas may be supplied to the plasma gun at varying ranges. For instance, the nitrogen gas flow rate may range from 100 to 200 SCFH and the hydrogen gas flow rate ranges from 5 to 15 SCFH. As shown at block 201, the plasma forming gas may be circulated around an electrical arc generated by striking of the anode and the cathode to generate the plasma plumes (3). The electrical arc may be generated by supplying electrical power ranging from 15kW to 25kW. At block 202, the inert gas may be supplied from the inert gas source to the system (10) through the inert gas shroud (2). The inert gas may be supplied around the plasma plumes (3) and may be configured to reduces the temperature of the plasma plumes (3). The inert gas may be supplied encompassing the plasma plumes (3) at a rate ranging from 8 SCFH to 12 SCFH.

At block 203, the iron-based alloy may be fed into a stream of the plasma plumes (3). The iron-based alloy powder may be fed to the stream of the plasma plumes (3) through the feeding unit (4) at a pre-determined feeding rate. The feeding rate of the iron-based alloy powder may range from 7 grams/minute to 10 grams/minute. Upon feeding the iron-based alloy powder into the plasma plumes (3), the plasma plumes (3) may melt the iron-based alloy powder. Since, the iron-based alloy powder fed into the plasma plumes (3) are of varying sizes, the particles such as small particles melt uniformly, the medium and large particles melt non-uniformly. Evenly melted and unevenly melted particles are directed on to the substrate (S) to be coated.

At block 204, the stream of the plasma plumes (3) including the melted iron-based powder particles may be directed onto the surface of the substrate (S) to be coated. The melted iron-based alloy powder may be sprayed on to the surface of the substrate (S) to form micropillars of pre-defined dimensions on the surface of the substrate (S). The pre-defined dimension of the micropillars may range from 5 microns to 10 microns. Since, the inert gas encompassing the plasma plumes (3) reduce the temperature of the plasma plumes (3), this condition aids in forming higher number of micropillars. The micropillar structures formed on the substrate (S) according to the present disclosure may be clearly viewed from FIG.3, which is an image obtained from the scanning electron microscope [SEN]. Further, the system (10) may be capable of traversing in one or more directions to completely coat the substrate (S) with the hydrophobic layer. The traversing speed of the system (10) may range from 520rpm to 560rpm. In an embodiment, the formation of the micropillars on the substrate (S) may provide hierarchical roughness to the coating. The micropillars formed replicate the superhydrophobic lotus leaf pattern. Also, the micropillars act as air-trapping pocket between the droplet and the micropillars. The said resulting in the water droplets sitting on a surface of air and the coating material, and hence, making the material hydrophobic.

Table-1: Optimized process parameters to obtain hydrophobic layer.
The Table-1 indicates optimized parameters employed in obtaining hydrophobic layer on the substrate (S) as disclosed hereinabove in the present disclosure.

Referring now to FIG.4, which depict the hydrophobic nature of the coated substrate (S). Part A of FIG.4 illustrates a static contact angle of the surfaces prepared by the method illustrated above. While part B depicts a digital image of the iron-based alloy powder coating with water droplets rolling on the surface. As observed from part A, the manipulated surfaces show contact angle (CA) of 110° which confirms the hydrophobic nature of the surface. Furthermore, it may be observed that the developed hydrophobic coatings may have retained the hydrophobic characteristics even in harsh environment such as high temperature and high corrosion and wear prone atmosphere, where the polymer and polymer-modified metal based hydrophobic coatings fails to satisfy.

In an embodiment, the hydrophobic coating developed by the method of the present disclosure may have robust, wear and corrosion-resistance. The substrate (S) that is coated with the hydrophobic coating may have superior mechanical properties such as wear and abrasion. Performance properties of the coated hydrophobic substrate (S) may include a relatively high thermal capability, a relatively long lifespan.

It is to be understood that a person of ordinary skill in the art may develop a system of similar configuration without deviating from the scope of the present disclosure. Such modifications and variations may be made without departing from the scope of the present disclosure. Therefore, it is intended that the present disclosure covers such modifications and variations provided they come within the ambit of the appended claims and their equivalents.

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, 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 description 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, 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 in the description.

Referral Numerals:
Description Reference number
Plasma spray system 10
Plasma gun 1
Inert gas shroud 2
Plasma plumes 3
Feeding unit 4
Substrate S
Flow diagram 201-204