CN113070192B

CN113070192B - Composite coating, preparation method and electric appliance

Info

Publication number: CN113070192B
Application number: CN202010009044.6A
Authority: CN
Inventors: 万鹏; 曹达华; 杨玲; 许智波; 黄韦铭; 南春来
Original assignee: Foshan Shunde Midea Electrical Heating Appliances Manufacturing Co Ltd
Current assignee: Foshan Shunde Midea Electrical Heating Appliances Manufacturing Co Ltd
Priority date: 2020-01-06
Filing date: 2020-01-06
Publication date: 2023-01-13
Anticipated expiration: 2040-01-06
Also published as: CN113070192A

Abstract

The invention discloses a composite coating, a preparation method and an electric appliance. The composite coating includes: a substrate, the material of which comprises metal, ceramic or glass; a substrate; an insulating layer formed on a surface of the base; and an electrothermal alloy layer formed on a surface of the insulating layer remote from the substrate, wherein the insulating layer has a porosity of not more than 5% in at least a part of the region. The porosity of the insulating layer is controlled within a certain range, so that the insulating property of the insulating layer can be effectively improved, the insulating layer is prevented from being broken down by high voltage, and the harsh preparation process is also avoided.

Description

Composite coating, preparation method and electric appliance

Technical Field

The invention relates to the field of household appliances, in particular to a composite coating, a preparation method and an electric appliance adopting the composite coating.

Background

Heating units are used in various household electrical appliances, such as air conditioners, electric heaters, cookers and stoves. Currently, the main heating modes of the heating unit include electromagnetic heating, hot plate heating and infrared heating. However, the current electromagnetic heating usually needs to adopt a relatively complex heating system, the heat transfer efficiency of the hot plate heating mode is relatively low, and in addition, the infrared heating is only suitable for partial cookware with high infrared absorption coefficient.

The electrothermal alloy layer as a novel heating mode is a resistance alloy which utilizes the resistance characteristic of metal to manufacture a heating element and has higher heat exchange efficiency, higher reliability, lower cost and better manufacturability.

However, the current electrothermal alloy layer technology still needs to be improved.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. To this end, an object of the present invention is to propose a composite coating that can be effectively applied to household electrical appliances, the composite coating comprising an electrothermal alloy coating, having at least one of the following advantages:

the binding force between the electrothermal alloy coating and the conductive coating, or the binding force between the substrate and the insulating layer, or the binding force between the electrothermal alloy coating and the insulating layer is remarkably improved;

the insulating layer has higher electrical insulation and can resist high voltage of 1250 volts or even 2500 volts without breakdown; and

the expansion coefficient of the electrothermal alloy coating is close to that of the insulating layer, the electrothermal alloy coating is not easy to deform, and the heating power of the electrothermal alloy coating can be improved.

The present invention has been completed based on the following findings of the inventors:

the inventor of the invention finds that the household appliance adopting the electrothermal alloy coating has the possibility of high-voltage breakdown of the insulating layer in the using process in the process of researching the electrothermal alloy coating. In order to avoid this, the inventors have conducted extensive analyses of the insulating layer and have unexpectedly found that there may be a certain number of voids in the insulating layer which reduce the insulating properties of the insulating layer during use of the appliance and which are hygroscopic during use of the appliance, thereby further reducing the insulating properties of the insulating layer. For this reason, the inventors have conducted intensive studies on the porosity, and found that when the porosity exceeds 5%, the insulating property of the insulating layer is deteriorated, and the moisture absorption of the insulating layer is increased, and there is a possibility that the insulating layer is broken down even by high voltage. In addition, the inventors have also found that the reduction in porosity causes the conditions of the manufacturing process to become severe, especially when the porosity is below 0.2%, especially below 0.1%. Therefore, the present inventors have conducted extensive studies on means for ensuring the insulation property of the insulating layer while maintaining a certain porosity, and finally completed the present invention.

In view of the above, the present invention provides a composite coating layer having an electrothermal alloy layer, which can be effectively applied to a household appliance.

In one aspect of the invention, the invention provides a composite coating, according to an embodiment of the invention, comprising: a substrate, the material of which comprises metal, ceramic or glass; an insulating layer formed on a surface of the base; and an electrothermal alloy layer formed on a surface of the insulating layer remote from the substrate, wherein the insulating layer has a porosity of not more than 5% in at least a part of the region. According to an embodiment of the present invention, the porosity of the insulating layer is not less than 0.1%. According to an embodiment of the invention, the porosity of the insulating layer does not exceed 2%. According to an embodiment of the invention, the porosity of the composite coating is 0.1-3% in at least a part of the area. The inventor finds that the insulating property of the insulating layer can be effectively improved by controlling the porosity of the insulating layer within a certain range, the insulating layer is prevented from being broken down by high voltage, and meanwhile, the harsh preparation process is also avoided.

According to the embodiment of the invention, the electrothermal alloy layer is an electrothermal alloy coating layer, the electrothermal alloy coating layer contains a metal element and an oxygen element, and the atomic percent of the oxygen element is 5-30 at% in at least one part of the electrothermal alloy coating layer. Therefore, the expansion coefficients of the electrothermal alloy coating and the insulating layer are close, the electrothermal alloy coating is not easy to deform, and the heating power of the electrothermal alloy coating can be improved.

According to an embodiment of the invention, the metal element comprises: 15 to 25at% of chromium element; 10 to 20at% of aluminum element; 0.1 to 1.5at% of yttrium element; and the balance of iron. Thereby, a high heating efficiency is obtained and the cost is relatively low.

According to an embodiment of the present invention, the electrothermal alloy layer is an electrothermal alloy coating comprising a plurality of electrothermal alloy coating sub-layers, which are sequentially stacked, and in at least one region of the electrothermal alloy coating, the oxygen content in the electrothermal alloy coating sub-layers decreases in a direction away from the insulating layer. Therefore, in the area close to the insulating layer, the electric heating alloy coating sublayer has relatively high oxygen content and can have an expansion coefficient close to the insulating layer, so that the electric heating alloy coating and the insulating layer are prevented from cracking, and meanwhile, in the area far away from the insulating layer, the electric heating alloy coating sublayer has relatively low oxygen content, so that the electric heating alloy coating can be ensured to have good conductivity.

According to an embodiment of the invention, the composite coating further comprises: a conductive layer formed on at least a portion of a surface of the electrothermal alloy layer, a material constituting the conductive layer including silver or copper. Therefore, the electrothermal alloy coating can be connected with an external circuit through the conducting layer, so that the composite coating has good electrothermal performance.

According to the embodiment of the invention, the conductive layer is a conductive coating, and on at least one section of the composite coating layer, which is vertical to the plane of the substrate, the profile of the interface of the conductive coating and the electrothermal alloy layer has a profile arithmetic mean deviation Ra of not less than 5 micrometers. According to an embodiment of the invention, the profile of the interface of the electrically conductive coating layer with the layer of electrothermal alloy has an arithmetic mean deviation Ra of the profile not lower than 20 micrometers. Therefore, the binding force between the conductive coating and the electrothermal alloy layer can be improved.

According to an embodiment of the invention, the insulation voltage of the composite coating is not less than 1250 volts. This improves the puncture resistance of the composite coating.

According to the embodiment of the invention, the insulating layer is an insulating coating, and on at least one section of the composite coating, which is perpendicular to the plane of the substrate, the interface profile of the substrate and the insulating layer has a profile arithmetic mean deviation Ra of not less than 20 micrometers. Thus, the bonding force between the substrate and the insulating layer can be improved.

According to the embodiment of the invention, the electrothermal alloy layer is an electrothermal alloy coating, and on at least one section of the composite coating, which is perpendicular to the plane of the substrate, the interface profile of the electrothermal alloy coating and the insulating layer has a profile arithmetic mean deviation Ra of not less than 5 micrometers. According to an embodiment of the invention, the profile of the interface of the electrocaloric alloy coating and the insulating layer has an arithmetic mean deviation Ra of the profile of not less than 20 micrometers. Therefore, the binding force between the electrothermal alloy coating and the insulating layer can be improved.

According to an embodiment of the invention, the layer of electrothermal alloy has a predetermined pattern. According to the embodiment of the invention, the electrothermal alloy layers are distributed at intervals on the section perpendicular to the plane of the substrate. The electric heating alloy layer and the insulating layer are not completely covered, so that heat is generated locally, the heat at the corresponding position of the insulating layer is higher, then the heat is diffused and transferred at other positions of the insulating layer, and the heat at the corresponding position of the substrate can also be relatively higher.

According to an embodiment of the invention, the composite coating further comprises: a protective member covering the electrothermal alloy layer. According to an embodiment of the invention, the protective element is a protective coating covering at least a part of the surface of the electrothermal alloy layer remote from the substrate; or the protection piece is an insulating protective shell, and the insulating protective shell covers at least one part of the surface of the electrothermal alloy layer far away from the base body. Thus, the composite coating can be ensured to be insulated from the outside.

According to an embodiment of the invention, the composite coating layer satisfies at least one of the following conditions: the thickness of the insulating layer is 50-500 microns; the thickness of the electrothermal alloy layer is 10-150 microns; the thickness of the conductive layer is 30-150 microns. Therefore, the composite coating has good service performance.

In a second aspect of the invention, an appliance is presented. According to an embodiment of the invention, the appliance comprises: a heating assembly having the composite coating described previously. Thus, according to embodiments of the present invention, the appliance may utilize the high heat generation efficiency of the composite coating. In addition, as mentioned above, by controlling the porosity of the insulating layer within a certain range, the insulating property of the insulating layer can be effectively improved, the insulating layer is prevented from being broken down by high voltage, and the harsh preparation process is also avoided. Therefore, the electric appliance adopting the composite coating has high safety and use reliability.

According to the embodiment of the invention, the electric appliance is a cooking appliance or a liquid heating container, and specifically comprises an air conditioner, a cleaning appliance, a kitchen appliance, an electric heating appliance and a face-lifting health-care appliance. According to an embodiment of the invention, the appliance comprises: the composite coating described above; the electrothermal coating comprises a body, wherein a part of the outer wall of the body forms a matrix of the composite coating, and the electrothermal alloy layer is arranged on the outer wall of the body. Therefore, the electric appliance has high safety and use reliability.

It should be noted that the features and advantages described above for the composite coating are also applicable to the electrical appliance according to the embodiment of the present invention, and are not described herein again.

In a third aspect of the invention, the invention proposes a method for preparing a composite coating as described above. According to an embodiment of the invention, the method comprises: (1) forming the insulating layer on a surface of the base; (2) Forming the electrothermal alloy layer on the surface of the insulating layer far away from the substrate, and enabling the porosity of the insulating layer to be not more than 5% in at least one part of area so as to obtain the composite coating. Therefore, the insulating property of the insulating layer can be effectively improved, and the insulating layer is prevented from being broken down by high voltage.

According to an embodiment of the present invention, the step (1) further comprises: (1-a) roughening at least a part of the surface of the substrate; and (1-b) forming the insulating layer on the roughened surface by explosion spraying or plasma spraying. According to an embodiment of the present invention, in the step (1), the roughening treatment is performed by at least one of sand blasting, grinding, and chemical etching, and in the step (2), the electrothermal alloy layer is formed by supersonic spraying or plasma spraying. According to an embodiment of the present invention, further comprising: forming a conductive coating on at least a portion of the surface of the electrothermal alloy coating by arc spraying or cold spraying. Therefore, an insulating layer, an electrothermal alloy coating and a conductive coating with an embedded structure at the interface can be formed. Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a schematic structural view of a composite coating according to one embodiment of the present invention;

FIG. 2 is a schematic structural view of a composite coating according to another embodiment of the invention;

FIG. 3 is a schematic structural view of a composite coating according to yet another embodiment of the present invention;

FIG. 4 is a schematic structural view of a composite coating according to yet another embodiment of the invention;

FIG. 5 is a schematic structural view of a composite coating according to yet another embodiment of the invention;

FIG. 6 is a schematic structural view of a composite coating according to yet another embodiment of the present invention;

FIG. 7 is a schematic structural view of a composite coating according to yet another embodiment of the invention;

FIG. 8 is a schematic structural view of a composite coating according to yet another embodiment of the invention;

FIG. 9 is a perspective view of a pot according to one embodiment of the present invention;

FIG. 10 is a bottom view of the pot according to one embodiment of the present invention;

fig. 11 is a bottom view of a pot according to yet another embodiment of the present invention.

Reference numerals:

a substrate 100, an insulating layer 200, an electrothermal alloy layer 300,

the number of the apertures 201 is such that,

an electrothermal alloy coating sublayer 310, an electrothermal alloy coating sublayer 320, an electrothermal alloy coating sublayer 330, an electrothermal alloy coating sublayer 340,

insulating layer sublayer 210, insulating layer sublayer 220, insulating layer sublayer 230, insulating layer sublayer 240,

conductive layer 400, conductive connection 410, power source 420,

the interface profile L10, the interface profile L20, the interface profile L30,

the protective coating 500a, the insulating protective shell 500b,

the cooker 1000, the cooker body 10, the cooker edge 11,

the first insulating layer 20 is formed of a first insulating material,

a heat-generating layer 30, a heat-generating section 31, a circular arc section 311, a first transition section 312, a straight section 313, a second transition section 314,

a first conductive layer 41, a second conductive layer 42.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention and are not to be construed as limiting the present invention.

A composite coating according to an embodiment of the present invention is described below with reference to fig. 1 to 8.

the inventor of the invention discovers that in the process of researching the electrothermal alloy coating, the situation that an insulating layer is broken down by high voltage can occur in the use process of the household appliance adopting the electrothermal alloy coating. In order to avoid this, the inventors have conducted extensive analyses of the insulating layer and have unexpectedly found that there may be a certain number of voids in the insulating layer which reduce the insulating properties of the insulating layer during use of the appliance and which are hygroscopic during use of the appliance, thereby further reducing the insulating properties of the insulating layer. For this reason, the inventors have made intensive studies on the porosity, and found that when the porosity exceeds 5%, the insulating property of the insulating layer is deteriorated, and the moisture absorption of the insulating layer is increased, and there is a possibility that the insulating layer is broken down even by high voltage. In addition, the inventors have also found that the reduction in porosity causes the conditions of the manufacturing process to become severe, especially when the porosity is below 0.2%, especially below 0.1%. Therefore, the present inventors have conducted extensive studies on means for ensuring the insulation property of the insulating layer while maintaining a certain porosity, and finally completed the present invention.

Referring to fig. 1, in one aspect of the present invention, the present invention proposes a composite coating including a substrate 100, an insulation layer 200 and an electrothermal alloy layer 300, wherein a material constituting the substrate 100 includes a metal, a ceramic or a glass, the insulation layer 200 is formed on a surface of the substrate 100, and the electrothermal alloy layer 300 is formed on a surface of the insulation layer 200 remote from the substrate 100, according to an embodiment of the present invention.

Referring to fig. 2, in accordance with an embodiment of the present invention, the insulating layer 200 has a porosity of no more than 5% in at least a portion of the region. According to an embodiment of the present invention, the porosity of the insulating layer 200 is not less than 0.1%. According to an embodiment of the present invention, the porosity of the insulating layer 200 does not exceed 2%. According to an embodiment of the invention, the porosity of the composite coating is 0.1-3% in at least a part of the area. The inventor of the present invention found in the process of studying the electrothermal alloy layer 300 that there is a possibility that the insulation layer 200 may be broken down by high voltage during the use of the household appliance using the electrothermal alloy layer 300. In order to avoid this, the inventors have conducted an in-depth analysis on the insulating layer 200 and found that the insulating layer 200 may be formed by a spray coating process, and in particular, by thermal spraying, and although the material used to form the insulating layer 200 has good insulating properties by itself, voids 201 may exist between particles due to melt stacking of the particles during the thermal spraying. The inventors have found that when the porosity in the insulating layer reaches a certain value, the insulating layer is broken down leading to a safety risk. Therefore, under the same porosity, the thicker the insulating layer thickness is, the better; the lower the porosity in the coating, the better the same insulation thickness. However, when the porosity is less than 0.1%, the required flame temperature of thermal spraying is as high as 10000 ℃ or more, the particle velocity for forming the insulating layer is more than 1000m/s, which is difficult to be achieved by the prior art, and the conditions of the preparation process become severe. In addition, the inventors have found that the bonding force between the insulating layer and the substrate 100 or the electrothermal alloy layer 300 is rapidly reduced when the thickness of the insulating layer exceeds 500 μm. In addition, the inventors have found that the pores 201 may be hygroscopic during use of the appliance, thereby further reducing the insulating properties of the insulating layer. For this reason, the inventors have conducted intensive studies on the porosity of the insulating layer, and found that when the porosity of the insulating layer exceeds 5%, the insulating property of the insulating layer 200 is deteriorated, and the moisture absorption of the insulating layer 200 is increased, and there is a possibility that the insulating layer is broken down even by high voltage. According to the embodiment of the invention, the inventor finds that the insulating property of the insulating layer can be effectively improved by controlling the porosity of the insulating layer within a certain range, the insulating layer is prevented from being broken down by high voltage, and meanwhile, a harsh preparation process is avoided. It should be noted that the insulating voltage of the composite coating is not lower than 1250V, which means that the composite coating is not broken down after 1250V is applied to the composite coating, and the voltage of the composite coating which is not broken down can reach 2500V at most.

According to an embodiment of the present invention, the electrothermal alloy layer 300 may be an electrothermal alloy coating, the electrothermal alloy coating 300 containing a metal element and an oxygen element, the oxygen element being present in an atomic percentage of not more than 40at% in at least a portion of the electrothermal alloy coating.

According to the embodiment of the invention, by adopting the electrothermal alloy coating 300, electric energy can be effectively converted into heat energy, the heating efficiency is high, uniform heating is easy, and the use and preparation cost can be reduced. However, in the process of research on the electrothermal alloy coating 300, the inventor of the present invention found that, in the use process of a household appliance using the electrothermal alloy coating 300, after multiple cycles of cooling and heating, deformation may occur between the insulating layer 200 and the electrothermal alloy coating 300, and fracture may seriously occur to cause electric leakage or short circuit. The inventor of the present invention has conducted intensive studies and analyzed various factors, and found that, because the components of the insulating layer 200 and the electrothermal alloy coating 300 are different, a large difference in thermal expansion coefficient exists between the insulating layer 200 and the electrothermal alloy coating 300, and further, after multiple cold and hot cycles, the insulating layer 200 and the electrothermal alloy coating 300 are deformed, thereby leading to a series of adverse consequences. Therefore, the inventors have conducted intensive studies and unexpectedly found that the introduction of oxygen into the electrothermal alloy coating layer 300 can reduce the difference in expansion coefficient between the electrothermal alloy coating layer 300 and the insulating layer 200, thereby reducing the thermal stress between the electrothermal alloy coating layer 300 and the insulating layer 200, and improving the bonding strength between the electrothermal alloy coating layer 300 and the insulating layer 200 and the life span during thermal cycle use. And it has been unexpectedly found that the introduction of oxygen is also beneficial in increasing the electrical resistance and heat generation efficiency of the electrothermal alloy coating 300. The oxygen content can be controlled by the spraying atmosphere, and with the increase of the oxygen element content, the expansion coefficient of the electrothermal alloy coating 300 and the expansion coefficient of the insulating layer 200 tend to be consistent, so that the deformation between the insulating layer 200 and the electrothermal alloy coating 300 is avoided when the electrothermal alloy coating undergoes cold and heat changes. In addition, as the inventors have intensively studied, it has been found that, as the content of oxygen increases, especially when the content of oxygen exceeds 40% (atomic number percentage, which is also referred to as "at%" in this specification), the resistance of the electrothermal alloy coating layer becomes large, the heating power of the electrothermal alloy coating layer 300 is reduced, the electrothermal alloy coating layer 300 is overheated, the life of the electrothermal alloy coating layer is shortened, and the electrical conductivity of the electrothermal alloy coating layer is rapidly deteriorated. Thus, according to the embodiment of the present invention, by controlling the content of oxygen element in the electrothermal alloy coating layer 300 to be within 40% (atomic percentage), the electrothermal alloy coating layer can have a high heat generation efficiency while avoiding deformation or cracking between the insulating layer and the electrothermal alloy coating layer, and the electrical conductivity of the electrothermal alloy coating layer 300 can be prevented from being deteriorated, so that the composite coating layer can be ensured to be used for a heating unit of an electric appliance such as a household appliance.

Further, according to an embodiment of the present invention, in at least a part of the area of the electrothermal alloy coating layer, the atomic percent of oxygen element is not less than 5at%. According to an embodiment of the invention, the atomic percentage of the oxygen element is 5-30 at% in at least a part of the area of the electrocaloric alloy coating. Therefore, the expansion coefficient between the insulating layer and the electrothermal alloy coating is further ensured to be close, and deformation and even cracking between the insulating layer and the electrothermal alloy coating are avoided when the electrothermal alloy coating undergoes cold and hot changes.

It is noted that the content of a specific element (including but not limited to oxygen element, metal element, etc.) in the coating layer can be determined by means well known to those skilled in the art, such as X-ray fluorescence spectroscopy, X-ray diffraction spectroscopy, scanning electron microscopy spectroscopy, atomic emission spectroscopy, inductively coupled plasma emission spectroscopy, ultraviolet-visible spectrophotometry, and electrochemical methods. It will be understood by those skilled in the art that, for a given material, when determining the content of a specific element, it is not necessary to determine the content of the whole material, but one or several sites may be detected, and an arithmetic average value may be taken as a detection result, for example, the content of oxygen element is determined by performing elemental analysis on more than 3 sites of the material to be detected, and an average value of the oxygen element contents of these sites is taken as a final detection result. In addition, one skilled in the art can use in situ detection or sample a particular coating before performing the detection, as the case may be.

According to the embodiment of the present invention, the type of metal of the electrothermal alloy coating that can be used is not particularly limited as long as it can be adapted to form a stable coating on the surface of the insulator and can generate a desired amount of heat when an electric current is passed. The electrothermal alloy coating which can be used includes both Ni-Cr system and Fe-Cr-Al system alloys, and some rare metal elements such as yttrium element may be added according to circumstances. To this end, according to an embodiment of the present invention, the metal element for forming the electrothermal alloy coating layer includes at least one selected from the group consisting of chromium element, aluminum element, yttrium element, iron element, manganese element, and nickel element. According to an embodiment of the present invention, the metal element includes: 15 to 25at% of chromium element; 10 to 20at% of aluminum element; 0.1 to 1.5at% of yttrium element; and the balance of iron element. Thus, high heating efficiency is achieved, and the cost is relatively low, and such elemental proportioning enables good compatibility between the electrothermal alloy coating layer 300 and the adjacent layers (the insulating layer 200, the conductive coating layer 400, or the protective coating layer 500 a) in the composite coating layer.

The means of forming the electrothermal alloy coating 300 according to the embodiment of the present invention is not particularly limited, and various known spraying methods may be employed. According to an embodiment of the present invention, the electrothermal alloy coating 300 may be formed by thermal spraying, such as supersonic spraying or plasma spraying. In the process of forming the electrothermal alloy coating layer 300, a desired oxygen element content can be easily obtained by controlling the supply amount of oxygen. For example, by adjusting the ratio of air and inert gas, the elemental oxygen content can be obtained. Additionally, referring to FIG. 3, an electrothermal alloy coating 300 may include a plurality of electrothermal

alloy coating sub-layers

310, 320, 330, and 340 disposed in a sequential stack, according to an embodiment of the present invention. One skilled in the art may use different elemental oxygen contents for these electrothermal

alloy coating sublayers

310, 320, 330, and 340 as desired. According to some examples of the invention, the amount of oxygen in the electrocaloric

alloy coating sublayers

310, 320, 330, and 340 decreases in a direction away from the insulating layer (i.e., bottom-to-top in fig. 3) in at least one region of the electrocaloric alloy coating 300. Thus, regions proximate to the insulating layer 200, such as the electrothermal alloy coating sub-layer 340, having a relatively high oxygen content, may have a coefficient of expansion close to that of the insulating layer 200, while regions distal from the insulating layer 200, such as the electrothermal alloy coating sub-layer 310, may have a relatively low oxygen content, which may ensure good electrical conductivity of the electrothermal alloy coating 300. It should be noted that the 4 electrothermal

alloy coating sublayers

310, 320, 330 and 340 illustrated in FIG. 3 are for convenience of description only, and those skilled in the art may arrange the electrothermal

alloy coating sublayers

310, 320, 330 and 340 according to the total thickness of the electrothermal alloy coating 300 or according to the need, for example, more than ten electrothermal alloy coating sublayers may be used. In addition, it should be noted that, for the plurality of electrothermal

alloy coating sub-layers

310, 320, 330 and 340, the oxygen content in the electrothermal

alloy coating sub-layers

310, 320, 330 and 340 decreases along the direction away from the insulating layer (i.e. the direction from bottom to top in fig. 3), and it does not mean that the oxygen content of the upper layer is lower than that of the lower layer between any two adjacent electrothermal alloy coating sub-layers, and here, only the trend of the oxygen content is described as a whole, and generally, the oxygen content of the outermost layer, such as the electrothermal alloy coating sub-layer 310 in the figure, is lower than that of the innermost layer, such as the electrothermal alloy coating sub-layer 340, and the fluctuation of the oxygen content of one or several layers may exist in the middle, which is allowed.

Additionally, in accordance with an embodiment of the present invention, the thickness of the electrothermal alloy coating 300 is 10 to 150 microns in at least a portion of the region. According to an embodiment of the present invention, the thickness of the electrocaloric alloy coating 300 is 30-150 microns. According to an embodiment of the present invention, the thickness of the electrocaloric alloy coating 300 is 50 microns. Thus, the electrothermal alloy coating 300 can effectively meet the heat requirement of household appliances such as cookware. It should also be noted that, for the composite coating, the thickness of each coating can be detected by various known means, and the final detection result can be determined by a method of arithmetic mean of multipoint detection. One skilled in the art will appreciate that different thicknesses of the electrothermal alloy coating 300 will result in different resistances and different heating powers.

The type of material of the substrate 100 that may be used for the composite coating according to the embodiment of the present invention is not particularly limited. According to some specific examples of the present invention, the base 100 is formed of at least one selected from the group consisting of metal, ceramic, and glass. According to some embodiments of the present invention, the metal may include at least one selected from aluminum, aluminum alloy, stainless steel, iron alloy and iron, such as 304 stainless steel, 430 stainless steel, and the like. These materials are commonly used in electric appliances such as home appliances, and have a good heat conduction property, and thus, can effectively conduct heat generated from the electrothermal alloy coating layer. Further, when the composite coating is applied to a household appliance, it may be convenient to directly use a part of the structure or component existing in the appliance as the substrate 100, for example, according to some embodiments of the present invention, the outer wall of the pot body of an electric cooker may be used as the substrate 100, and further, other coatings of the composite coating may be formed on such substrate 100.

In addition, regarding the insulating layer 200, the insulating layer 200 may be formed of aluminum oxide, silicon oxide, or aluminum nitride according to an embodiment of the present invention. Alumina can be present in the form of ceramic materials, which have good insulating properties, and can have good compatibility with a variety of metal alloys and matrix materials. According to an embodiment of the invention, the insulation voltage of the composite coating is not less than 1250 volts. According to an embodiment of the invention, the insulation voltage of the composite coating is not lower than 2500 volts. Therefore, the insulating layer can have satisfactory insulating performance, so that the situation that the insulating layer is broken down by high voltage does not occur in the using process of the household appliance adopting the composite coating.

According to an embodiment of the present invention, the insulating layer 200 has a thickness of 50 to 500 μm in at least a portion of the region. According to the embodiment of the invention, the thickness of the insulating layer is 100-300 micrometers. According to an embodiment of the invention, the thickness of the insulating layer is 200 microns. The inventors of the present invention have found through experiments that, when the thickness of the insulating layer is controlled within the above range, the insulating layer still has satisfactory insulating properties and can ensure strong bonding strength between the insulating layer 200 and other coating layers, such as the electrothermal alloy coating 300 or the substrate 100, on the premise that the porosity is higher than 0.1%, for example, higher than 0.2%.

In addition, one skilled in the art can form the insulating layer 200 by spray coating, such as a plasma spray coating process, and can achieve a range of porosity (also sometimes referred to as porosity) by controlling parameters of the plasma spray coating process. Referring to fig. 4, in further accordance with an embodiment of the present invention, the insulating layer 200 may include a plurality of insulating

layer sub-layers

210, 220, 230, and 240, which are sequentially stacked. One skilled in the art may employ different porosities for the insulating

layer sub-layers

210, 220, 230, and 240 as desired. According to some examples of the invention, the porosity in the insulating

layer sub-layers

210, 220, 230 and 240 increases in a direction away from the insulating layer (a bottom-up direction in the figure). Thus, the insulating layer sub-layer 240 has relatively low porosity and high insulating properties in a region close to the substrate 100, and the insulating layer sub-layer 210 has relatively high porosity in a region far from the substrate 100, so that the manufacturing cost can be reduced. It should be noted that the 4 insulating

layer sub-layers

210, 220, 230 and 240 are shown in the drawings for convenience of description, and a person skilled in the art may set the number of the insulating layer sub-layers according to the total thickness of the insulating layer 200 or according to the requirement, for example, ten or more insulating layer sub-layers may be used. In addition, it should be particularly noted that, for the plurality of insulating

layer sub-layers

210, 220, 230 and 240, the porosity in the insulating

layer sub-layers

210, 220, 230 and 240 increases along the direction away from the substrate, and does not mean that the requirement is satisfied between any two adjacent insulating layer sub-layers, and the trend is only described as a whole.

The porosity of the insulating layer can be determined by one skilled in the art using techniques known in the art, for example, by taking a cross-sectional view of the composite coating and measuring the area fraction of pores 201 in the insulating layer 200 per unit area. It will be appreciated by those skilled in the art that by taking an average of a plurality of porosity values based on a plurality of cross sections, the porosity of the final insulating layer 200 may be determined. In addition, one skilled in the art can also refer to drainage methods to determine the porosity of the composite coating as a whole. Thus, according to embodiments of the present invention, the porosity of the composite coating is 0.1 to 3% in at least a portion of the area. Therefore, the breakdown voltage resistance of the composite coating can be improved, and the safety of the composite coating in the using process is improved.

According to an embodiment of the present invention, referring to fig. 6, the composite coating further includes: and a conductive layer 400, the conductive layer 400 being formed on at least a portion of a surface of the electrothermal alloy coating layer 300, a material constituting the conductive layer 400 including silver or copper. Therefore, the electrothermal alloy coating can be connected with an external circuit through the conducting layer, so that the composite coating has good electrothermal performance.

According to an embodiment of the present invention, the conductive layer 400 may be a conductive coating. The inventor of the invention finds that after a plurality of cold and hot cycles, the household appliance adopting the electrothermal alloy coating can be separated from the substrate, or the electrothermal alloy coating is separated from the conductive coating, or the electrothermal alloy coating is separated from the insulating layer. After the inventors have conducted extensive analysis, it is found that the bonding force between the respective coating layers is not easily increased due to the different types of materials used for the substrate, the insulating layer, the conductive coating layer, and the electrothermal alloy coating layer. For this reason, the inventors have conducted intensive studies and found that the bonding force between adjacent coating layers can be effectively improved under the same spray conditions by improving the roughness of the interface between the adjacent coating layers.

According to an embodiment of the present invention, referring to fig. 6, in order to improve the bonding force between the electrothermal alloy coating layer and the insulating layer, the profile L30 of the interface between the electrothermal alloy coating layer and the insulating layer has a profile arithmetic mean deviation Ra of not less than 5 μm in at least one section of the composite coating layer perpendicular to the plane of the substrate. According to an embodiment of the invention, the electrothermal alloy coating and insulating layer interface profile L30 has an arithmetic mean deviation of profile Ra of not less than 20 microns, such as 20 microns, 25 microns, 30 microns, 40 microns. In other words, for example, the thickness of the electrothermal alloy coating is 100 μm, the arithmetic mean deviation Ra of the interface profile of the electrothermal alloy coating and the insulating layer is 20%, 25%, 30%, 40% of the thickness of the electrothermal alloy coating. According to an embodiment of the invention, the electrothermal alloy coating-insulating layer interface profile L30 has a maximum height Rz of not less than 8 microns. According to an embodiment of the invention, the electrothermal alloy coating-insulating layer interface profile L30 has a maximum height Rz of not less than 25 microns. Therefore, the phenomenon of separation between layers due to thermal stress between the electrothermal alloy coating and the insulating layer can be reduced, the contact area between the electrothermal alloy coating and the insulating layer can be increased, the transfer of heat to a substrate through the insulating layer can be accelerated, further, the transition connection of mutual embedding is adopted, the heat generated by the electrothermal alloy coating is more, the heat conduction speed of the electrothermal alloy coating is higher, the heat conduction speed of the insulating layer is relatively lower, the transition structure connection of mutual embedding is arranged, the contact area is increased, the heat transfer efficiency between the interface of the electrothermal alloy coating and the insulating layer is improved, on one hand, the phenomenon of large thermal stress generated by overlarge temperature difference between the electrothermal alloy coating and the insulating layer is prevented, the phenomenon of separation between the electrothermal alloy coating and the insulating layer is enabled to be generated, on the other hand, the corrosion phenomenon generated by the thermal stress of the electrothermal alloy coating can be reduced, the service life of the electrothermal alloy coating is prolonged, further, the heat of the electrothermal alloy coating can be quickly guided into the insulating layer, the heat conduction efficiency of the insulating layer is accelerated, and the heating efficiency of the substrate is improved.

According to an embodiment of the present invention, referring to fig. 6, in order to improve the bonding force between the electrothermal alloy coating and the conductive coating, an interface profile L20 of the conductive coating 400 and the electrothermal alloy coating 300 has an arithmetic mean deviation Ra of the profile of not less than 5 μm in at least one section of the composite coating perpendicular to the plane of the substrate. According to an embodiment of the present invention, the interface profile L20 of the electrically conductive coating 400 and the electrothermal alloy coating 300 has an arithmetic mean deviation Ra of the profile of not less than 20 microns, such as 20 microns, 25 microns, 30 microns, 40 microns. In other words, for example, for a 100 μm thick electrocaloric alloy coating, the arithmetic mean deviation Ra of the interface profile of the electrocaloric alloy coating and the conductive coating is 20%, 25%, 30%, 40% of the thickness of the electrocaloric alloy coating. According to an embodiment of the present invention, the interface profile L20 of the electrically conductive coating 400 and the electrothermal alloy coating 300 has a maximum height Rz of not less than 8 microns. According to an embodiment of the present invention, the interface profile L20 of the electrically conductive coating 400 and the electrothermal alloy coating 300 has a maximum height Rz of not less than 25 microns. Because the types of materials used for the conductive coating 400 and the electrothermal alloy coating 300 are different, a structure in which the conductive coating 400 and the electrothermal alloy coating 300 are inlaid into each other can be formed according to the roughness of the interface, so that the bonding force between the conductive coating 400 and the electrothermal alloy coating 300 can be effectively improved, the contact area can be effectively increased, and the transmission efficiency of current can be improved.

According to an embodiment of the present invention, referring to fig. 6, in order to improve the bonding force between the insulating layer and the substrate, an interface profile L10 of the substrate 100 and the insulating layer 200 has a profile arithmetic mean deviation Ra of not less than 20 μm in at least one section of the composite coating layer perpendicular to a plane of the substrate. According to an embodiment of the present invention, the interface profile L10 of the substrate 100 and the insulating layer 200 has an arithmetic mean deviation Ra of the profile of not less than 30 micrometers, such as 40 micrometers, 50 micrometers, 60 micrometers. In other words, for an insulating layer having a thickness of 200 μm, the arithmetic mean deviation Ra of the interface profile between the insulating layer and the substrate is 20%, 25%, 30% of the thickness of the insulating layer. According to an embodiment of the present invention, the interface profile L10 of the substrate 100 and the insulating layer 200 has a maximum height Rz of not less than 25 μm. According to an embodiment of the present invention, the interface profile L10 of the substrate 100 and the insulating layer 200 has a maximum height Rz of not less than 35 μm. As described above, by increasing the roughness of the interface between adjacent coatings, the bonding force between adjacent coatings can be effectively increased under the same spray condition. Specifically, according to the roughness of the interface, a structure in which the insulating layer 200 is embedded in the substrate 100 may be formed, so that the bonding force between the two may be effectively improved. In addition, under the condition that the cross section between the substrate 100 and the insulating layer 200 has a certain roughness, the outer surface of the formed insulating layer 200, which is far away from the substrate 100, also has a certain roughness, so that the bonding force between the electrothermal alloy coating 300 and the insulating layer 200 sprayed on the outer surface is further enhanced, and further, the method is also helpful for promoting the bonding force between the electrothermal alloy coating 300 and the conductive coating 400, increasing the bonding area of the electrothermal alloy coating 300 and the conductive coating 400, and improving the current transmission efficiency.

The surface of the substrate 100 may be roughened as required before the insulating layer 200 is provided, for example, by sand blasting or sanding, preferably by sand blasting, so that the degree of roughness can be easily controlled, and for example, sand blasting with a particle size of 50 to 100 μm may be performed at a pressure of 0.8 to 1.5MPa for 10 to 200 seconds.

According to an embodiment of the invention, the arithmetic mean deviation Ra of the profile of the interface between the insulating layer and the substrate is greater than the arithmetic mean deviation Ra of the profile of the interface between the insulating layer and the electrothermal alloy coating and greater than the arithmetic mean deviation Ra of the profile of the interface between the electrothermal alloy coating and the conductive coating. Therefore, the binding force between layers can be improved, heat generated by the electrothermal alloy coating can be quickly transferred to the insulating layer, the efficiency and uniformity of heat transfer from the insulating layer to the substrate are improved, the thermal stress between the substrate and the insulating layer is reduced, and the delamination phenomenon between the substrate and the insulating layer is prevented.

It will be understood by those skilled in the art that the terms arithmetic mean deviation Ra and maximum height Rz of the profile as used herein are common parameters for evaluating the surface profile of an object, and those skilled in the art can perform detection by well-known means after acquiring an interface image, for example, the national standard GB/T1031-2009 describes a specific detection method: the arithmetic mean deviation Ra of the profile is the arithmetic mean of the absolute values of the distances from each point on the measured profile to the datum line in the sampling length; the maximum height Rz is the sum of the average of the peak heights of the five maximum profiles and the average of the valley bottoms of the five maximum profiles over the measured profile over the sample length.

Referring to fig. 5 and 8, the electrothermal alloy coating 300 can generate a large amount of heat when current passes through it, and in the embodiment of the present invention, it is proposed that the current is supplied to the electrothermal alloy coating 300 through the conductive coating 400, and the conductive coating 400 has a large contact area with the electrothermal alloy coating 300, so that the transmission efficiency of the current can be improved. According to embodiments of the present invention, the conductive coating may have a thickness of 30-150 microns. Therefore, the conductive coating has good conductive performance. According to an embodiment of the present invention, the composite coating further comprises a conductive connector 410, one end of the conductive connector 410 is connected to the conductive coating 400, and the other end of the conductive connector 410 is adapted to be connected to a power source 420. According to an embodiment of the present invention, at least one of the conductive connecting member 410 and the conductive coating 00 is a low heat generating material, for example, formed of copper or silver. Therefore, in the process that the power supply 420 supplies power to the electrothermal alloy coating 300 through the conductive connecting piece 410 and the conductive coating 400, the conductive connecting piece 410 does not generate excessive heat, so that the phenomenon that the connection between the conductive connecting piece 410 and the power supply 420 is hot-melted in the working process of the electrothermal alloy coating 300 is avoided, and further the conductive connecting piece 410 and the power supply 420 can be connected by adopting a metal material with a relatively low melting point, for example, in a soldering manner, so that the production cost is reduced.

According to an embodiment of the invention, the electrocaloric alloy coating has a predetermined pattern. According to the embodiment of the invention, the electrothermal alloy coatings are distributed at intervals on the interface vertical to the plane of the substrate. The electrothermal alloy coating and the insulating layer are not completely covered, so that heat is generated locally, the heat at the corresponding position of the insulating layer is higher, then the heat is diffused and transferred at other positions of the insulating layer, and the heat at the corresponding position of the corresponding substrate is also possibly relatively higher.

Referring to fig. 7 and 8, additionally, according to an embodiment of the present invention, the composite coating may further have a protection means, for example, a

protector

500a, 500b, the

protector

500a, 500b covering at least a portion of the electrothermal alloy coating 300. According to an embodiment of the present invention, the protection member is a protective coating 500a, and the protective coating 500a covers at least a portion of the surface of the electrothermal alloy coating 300 remote from the substrate 100. According to an embodiment of the present invention, the protection member is an insulating protective shell 500b, and the insulating protective shell 500b may cover at least a portion of the surface of the electrothermal alloy coating 300 away from the substrate 100. Therefore, the electrothermal alloy coating can be further protected, electric shock of a user in the use process is avoided, and short circuit of the electrothermal alloy coating caused by air or other materials in the use process can also be avoided. It will be appreciated by those skilled in the art that the protector is preferably made of an insulating material. For example, the protective member may be a ceramic coating, an insulating varnish, or an insulating structural member such as a plastic shell.

It should be noted that the features and advantages described above for the respective coatings or components may be combined with each other and are described separately for convenience only and will not be described again here.

As previously mentioned, the composite coatings described herein may be used in the home appliance field as heating components for home appliances and can exert their various advantages. Thus, in a second aspect of the invention, the invention proposes an electrical appliance. According to an embodiment of the invention, the appliance comprises: a heating assembly having the composite coating described previously. Thus, according to embodiments of the present invention, the appliance may utilize the high heat generation efficiency of the composite coating. In addition, as mentioned above, by controlling the porosity of the insulating layer within a certain range, the insulating property of the insulating layer can be effectively improved, the insulating layer is prevented from being broken down by high voltage, and simultaneously, the harsh spraying process is also prevented from being adopted. Therefore, the electric appliance adopting the composite coating has high safety and use reliability.

According to the embodiment of the present invention, the field to which the composite coating can be applied is not particularly limited, and applicable appliances include cooking appliances or liquid heating containers, and specifically, air conditioners, cleaning appliances, kitchen appliances, electric warming appliances, and cosmetic health care appliances.

Referring to fig. 9 to 11, according to an embodiment of the present invention, the electric appliance is a pot 1000 including the aforementioned composite coating and a pot body 10, a portion of an outer wall of the pot body 10 constitutes a matrix of the composite coating, and the electric heating alloy coating 300 is disposed on the outer wall of the pot body 10.

In order to improve the heating efficiency of the electrothermal alloy coating, according to the embodiment of the invention, the electrothermal alloy coating 300 forms the heat generating layer 30 of the pot 1000 on the pot body, the heat generating layer comprises a plurality of heat generating sections 31 connected end to end in sequence, the head end of the first heat generating section 31 in the plurality of heat generating sections 31 is suitable for being connected with the power input end of the heating circuit, and the tail end of the last heat generating section 31 in the plurality of heat generating sections 31 is suitable for being connected with the power output end of the heating circuit.

Therefore, the heating layer 30 is divided into the plurality of heating sections 31 which are connected in series, a loop can be formed during electrification, wherein the heating sections 31 can be one or two combinations of straight lines and circular arcs, so that the heating layer 30 is attractive in arrangement, simple in manufacturing process and high in utilization rate.

In some embodiments, a portion of the plurality of heat-generating segments 31 is an arc segment 311, another portion of the plurality of heat-generating segments 31 is a first transition segment 312, a center of a circle corresponding to the plurality of arc segments 311 is a center of a bottom wall of the pot body, and at least a portion of the plurality of arc segments 311 is arranged at intervals in a radial direction of a circumference with the center of the bottom wall of the pot body as a center, that is, a circle corresponding to at least a portion of the plurality of arc segments 311 is arranged concentrically. In the extending direction of the heat generating layer 30, the plurality of arc segments 311 are arranged at intervals, the plurality of first transition segments 312 are arranged at intervals, two adjacent arc segments 311 are connected through the first transition segment 312, and the arc segments 311 are connected between two adjacent first transition segments 312. The plurality of arc sections 311 and the plurality of first transition sections 312 are connected in series, so that a loop can be formed during electrification, uniform heating is realized, the heating layer 30 is attractive in arrangement, the manufacturing process is simple, and the utilization rate is high. In some examples, the first transition section 312 is a straight or arcuate section. Specifically, in the present embodiment, two adjacent circular arc segments 311 are connected by a straight line segment. In the present embodiment, two adjacent circular arc segments 311 are connected by a circular arc transition.

In some embodiments, a portion of the plurality of heat-generating segments 31 is a straight segment 313, another portion of the plurality of heat-generating segments 31 is a second transition segment 314, and at least a portion of the plurality of straight segments 313 are arranged in parallel or in a line. In the extending direction of the heat generating layer 30, a plurality of straight sections 313 are arranged at intervals, a plurality of second transition sections 314 are arranged at intervals, two adjacent straight sections 313 are connected through the second transition sections 314, and two adjacent second transition sections 314 are connected through the straight sections 313. The plurality of straight sections 313 and the plurality of second transition sections 314 are connected in series, so that a loop can be formed when the power is on, uniform heating is realized, the heating layer 30 is beautiful in arrangement, the manufacturing process is simple, and the utilization rate is high.

In some examples, the second transition section 314 forms an arc section and the circle center corresponding to the arc section is the center of the bottom wall of the pan body; and/or the second transition section 314 forms a straight line segment. Specifically, two adjacent straight sections 313 may be connected by a circular arc section and a straight section.

Since the current always flows along the path with the shortest distance, if the corner formed between two adjacent heat generating sections 31 is a right angle, and particularly, if the current is easily accumulated at the place where the inner corner is a right angle, the right angle current is too high, the local temperature of the heat generating layer 30 is too high if the current is light, and the local heat generating section 31 of the heat generating layer 30 is easily burned out if the current is heavy, and even a short circuit is easily generated. Therefore, in some embodiments, two adjacent heat generation sections 31 are connected in a circular arc transition manner.

In order to prevent the heating section 31 from being worn or damaged to affect the heating effect of the pot body 10, in some embodiments, the width D2 of the heating section 31 is set to be 0.1mm to 30mm. For example, the width D2 of the heat emitting segment 31 may be 0.1mm, 10mm, 15mm, 20mm, 25mm, 30mm. In some examples, the width D2 of the heat emitting segment 31 is set to 5mm to 12mm.

It should be noted that too large distance D1 between two adjacent spaced-apart heat-generating segments 31 may result in poor uniformity of heating temperature, too small distance D1 between two adjacent spaced-apart heat-generating segments 31 may result in small creepage distance for the first heat generation, and if there is a foreign matter between two adjacent spaced-apart heat-generating segments 31 or due to environmental moisture, an arc may be easily generated, thereby damaging heat-generating layer 30.

Therefore, in some embodiments, the distance D1 between two adjacent spaced heating segments 31 is set to be 0.1mm to 20mm. For example, the distance D1 between two adjacent spaced-apart heat emitting segments 31 may be 0.1mm, 5mm, 8mm, 12mm, 15mm, 20mm. In some examples, the distance D1 between two adjacent spaced heat emitting segments 31 is 5mm to 10mm, for example, the distance D1 between two adjacent spaced heat emitting segments 31 may be 5mm, 7mm, 10mm.

Other components of the appliance according to embodiments of the present invention, such as power supplies, control components, etc., and operations, are known to those of ordinary skill in the art and will not be described in detail herein.

In another aspect of the invention, the invention provides a method of making the composite coating described above. According to an embodiment of the invention, the method comprises:

(1) An insulating layer is formed on a surface of the base. According to an embodiment of the present invention, the step (1) further comprises; (1-a) roughening at least a part of a surface of a substrate; (1-b) forming an insulating layer on the roughened surface by explosion spraying or plasma spraying, the insulating layer having a porosity of not more than 5%. Therefore, the insulating layer has high compactness, so that the composite coating has high breakdown resistance, and the surface of the substrate has certain roughness, so that the bonding force between the insulating layer and the substrate can be further enhanced. According to an embodiment of the present invention, the roughening treatment is performed by at least one of sand blasting, grinding and chemical etching. Preferably, a sand blast treatment is used so that the degree of roughness can be easily controlled, and for example, a sand blast with a particle size of 50 to 100 μm is performed at a pressure of 0.8 to 1.5MPa for 10 to 200 seconds.

(2) Forming an electrothermal alloy coating on the surface of the insulating layer remote from the substrate so as to obtain a composite coating. According to an embodiment of the present invention, the electrothermal alloy coating layer may be formed by supersonic spraying or plasma spraying.

By this method, the aforementioned composite coating can be efficiently obtained. As mentioned above, by controlling the porosity of the insulating layer within a certain range, the insulating property of the insulating layer can be effectively improved, the insulating layer is prevented from being broken down by high voltage, and the harsh spraying process is also avoided. Thereby, it can be ensured that the composite coating can be used for a heating unit of an appliance, such as a household appliance.

According to the embodiment of the present invention, the method may further include: (3) And forming a conductive coating on the surface of the electrothermal alloy coating layer far away from the insulating layer by electric arc spraying or cold spraying.

It should be noted that the features and advantages described above for the composite coating are also applicable to the method for preparing the composite coating according to the embodiment of the present invention, and will not be described herein again. In addition, regarding the formation process of the coating layer, it is well known in the art, and those skilled in the art can accomplish it according to the process conditions selected as described herein without inventive labor.

The scheme of the invention will be explained with reference to the examples.

It will be appreciated by those skilled in the art that the following examples are illustrative of the invention only and should not be taken as limiting the scope of the invention. The examples do not specify particular techniques or conditions, and are performed according to techniques or conditions described in literature in the art or according to the product specification. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.

Example 1

Preparation of composite coatings

After the surface cleaning treatment is carried out on the stainless steel material, the surface of the stainless steel is subjected to sand blasting treatment, and the surface profile of the stainless steel substrate is made to have the profile arithmetic mean deviation Ra of 40 micrometers by controlling the conditions of the sand blasting treatment.

And spraying an insulating layer on the surface of the stainless steel material subjected to sand blasting through a plasma spraying process, wherein the insulating layer is made of aluminum oxide, and the porosity of the insulating layer is ensured to be 3% by adjusting spraying parameters, and the thickness of the insulating layer is 200 microns. The interface profile of the insulating layer and the stainless steel substrate had an arithmetic mean deviation Ra of the profile of 40 micrometers.

On the surface of the formed insulating layer, feCrAlY powder (iron (Fe): 35-45at%, chromium (Cr): 15-25 at%, aluminum (Al): 10-20at%, yttrium (Y): 0.1-1.5 at%) was sprayed by supersonic flame, and the amount of oxygen supplied was controlled so that the oxygen content of the electrothermal alloy coating was 20at%, thereby forming an electrothermal alloy coating having a thickness of 50 μm. The profile of the interface of the electrocaloric alloy coating and the insulating layer has an arithmetic mean deviation Ra of the profile of 20 microns.

Copper is sprayed on the surface of the formed electrothermal alloy coating through cold spraying, so that a conductive coating with the thickness of 50 micrometers is formed. The interface profile of the conductive coating and the electrothermal alloy coating has an arithmetic mean deviation Ra of the profile of 20 microns.

Cross section detection

The cross section of the obtained composite coating is detected, and the result shows that an obvious mutual mosaic structure is formed between the copper layer (conductive coating) and the FeCrAlY layer (electrothermal alloy coating), and in addition, a cross structure is also formed between the alumina layer (insulating layer), the FeCrAlY layer (electrothermal alloy coating) and the stainless steel layer (substrate).

Performance detection

In this example, the bonding strength of the composite coating obtained in example 1 was examined 1000 times by cold and hot cycles (room temperature-400 degrees celsius), and it was found that no significant cracking occurred between the layers.

In this example, the breakdown resistance of the composite coating was also tested and it was found that the material was able to withstand a voltage of 1250-2500V without being broken down.

Example 2 to example 6

Examples 2 to 6 were prepared by substantially the same procedure as in example 1, except that the surface of the stainless steel was not subjected to the sand blast treatment and the oxygen content in the electrothermal alloy coatings of examples 2 to 6 was controlled to 10at%, 15at%, 25at%, 30at%, and 35at% respectively when the surface of the insulating layer was subjected to the supersonic flame spraying of the FeCrAlY powder.

The bonding strength of the composite coatings obtained in examples 2-6 was tested by hot and cold cycles (room temperature-400 ℃) for 1000 times, and it was found that no significant cracking occurred between the insulating layer and the electrothermal alloy coating in the composite coating.

Example 7 example 10

Examples 7-10 were prepared substantially the same as in example 1, except that, when the insulating layer was sprayed by a plasma spray process, the spray parameters (e.g., spray speed, spray pressure, spray temperature) were adjusted such that the porosity of the insulating layer in example 7 was 1% and the thickness was 100 μm, the porosity of the insulating layer in example 8 was 2% and the thickness was 200 μm, the porosity of the insulating layer in example 9 was 4% and the thickness was 400 μm, and the porosity of the insulating layer in example 10 was 5% and the thickness was 400 μm.

The breakdown resistance of the composite coatings obtained in examples 7 to 10 was examined, and it was found that the above composite coatings can withstand a voltage of 1250 to 2500V without being broken down.

Examples 11 and 12

The composite coatings of examples 11 and 12 were prepared in substantially the same manner as in example 1, except that the stainless steel substrate and the insulating layer had an arithmetic mean deviation of profile Ra of 30 μm in the profile of the interface between the insulating layer and the electrocaloric alloy coating and the electrothermal alloy coating and the conductive coating, respectively, in example 11 by controlling the conditions of the blasting process when the stainless steel surface was subjected to the blasting process; let the profile of the interface of the stainless steel substrate and the insulating layer in example 12 have an arithmetic mean deviation Ra of the profile of 50 micrometers, the profile of the interface of the insulating layer and the electrocaloric alloy coating layer, and the profile of the interface of the electrocaloric alloy coating layer and the conductive coating layer have an arithmetic mean deviation Ra of the profile of 30 micrometers, respectively.

Cross-section detection of the composite coatings obtained in examples 11 and 12 shows that obvious mutual mosaic structures are formed between the conductive coating and the electrothermal alloy coating, and cross structures are formed between the insulating layer and the electrothermal alloy coating as well as between the insulating layer and the substrate.

The bonding strength of the composite coatings obtained in examples 11 and 12 was examined by hot and cold cycles (room temperature-400 degrees celsius) 1000 times, and it was found that no significant cracks occurred between the layers.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples" or the like mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A composite coating, comprising:

a substrate, a material constituting the substrate including metal, ceramic or glass;

an insulating layer formed on a surface of the base; and

an electrothermal alloy layer formed on the surface of the insulating layer far away from the substrate, wherein the electrothermal alloy layer is an electrothermal alloy coating containing a metal element and an oxygen element, and the atomic percentage of the oxygen element is 5-30 at% in at least one partial region of the electrothermal alloy coating;

the electrothermal alloy coating comprises a plurality of electrothermal alloy coating sub-layers which are sequentially arranged in a laminated manner, and the oxygen content in the electrothermal alloy coating sub-layers is reduced in a direction away from the insulating layer in at least one region of the electrothermal alloy coating;

the electrothermal alloy layer is provided with a preset pattern, and the electrothermal alloy layer is distributed at intervals on the section vertical to the plane of the substrate;

wherein, in at least a part of the region, the porosity of the insulating layer is not more than 5%.

2. The composite coating of claim 1, wherein the porosity of the insulating layer is not less than 0.1%.

3. The composite coating of claim 1, wherein the porosity of the insulating layer is no more than 2%.

4. The composite coating of claim 1, wherein the porosity of the composite coating is between 0.1 and 3% in at least a portion of the area.

5. The composite coating of claim 1, wherein the metallic element comprises:

15 to 25at% of chromium element;

10 to 20at% of aluminum element;

0.1 to 1.5at% of yttrium element; and

the balance of iron element.

6. The composite coating of claim 1, further comprising:

a conductive layer formed on at least a portion of a surface of the electrothermal alloy layer, a material constituting the conductive layer including silver or copper.

7. The composite coating of claim 6, wherein the electrically conductive layer is an electrically conductive coating, and wherein the profile of the interface of the electrically conductive coating with the layer of electrothermal alloy has an arithmetic mean deviation Ra of the profile of not less than 5 μm in at least one cross-section of the composite coating perpendicular to the plane of the substrate.

8. The composite coating of claim 7, wherein the interface profile of the electrically conductive coating with the layer of electrothermal alloy has an arithmetic mean deviation Ra of the profile of not less than 20 micrometers.

9. The composite coating of claim 1, wherein the composite coating has an insulation voltage of not less than 1250 volts.

10. The composite coating of claim 1, wherein the insulating layer is an insulating coating, and the composite coating has an interface profile with the insulating layer having an arithmetic mean deviation Ra of the profile of not less than 20 μm in at least one cross section perpendicular to the plane of the substrate.

11. The composite coating of claim 1, wherein the electrothermal alloy layer is an electrothermal alloy coating, and the interface profile of the electrothermal alloy coating and the insulating layer has an arithmetic mean deviation Ra of profile of not less than 5 μm in at least one cross section of the composite coating perpendicular to the plane of the substrate,

alternatively, the profile of the interface of the electrothermal alloy coating layer and the insulating layer has an arithmetic mean deviation Ra of the profile of not less than 20 micrometers.

12. The composite coating of claim 1, further comprising:

a protective member covering the electrothermal alloy layer.

13. The composite coating of claim 12, wherein the protective element is a protective coating covering at least a portion of the surface of the electrothermal alloy layer remote from the substrate; or

The protection piece is an insulating protective shell, and the insulating protective shell covers at least one part of the surface of the electrothermal alloy layer far away from the base body.

14. The composite coating according to claim 6, wherein the composite coating satisfies at least one of the following conditions:

the thickness of the insulating layer is 50-500 microns;

the thickness of the electrothermal alloy layer is 10-150 microns;

the thickness of the conductive layer is 30-150 micrometers.

15. An electrical appliance, comprising:

a heating element having a composite coating as claimed in any one of claims 1 to 14.

16. The electric appliance according to claim 15, characterized in that it is a cooking appliance or a liquid heating container, comprising:

a composite coating as claimed in any one of claims 1 to 14;

the electrothermal coating comprises a body, wherein a part of the outer wall of the body forms a matrix of the composite coating, and the electrothermal alloy layer is arranged on the outer wall of the body.

17. A method of making the composite coating of any one of claims 1-14, comprising:

(1) Forming the insulating layer on a surface of the base;

(2) Forming the electrothermal alloy layer on the surface of the insulating layer far away from the substrate, and enabling the porosity of the insulating layer to be not more than 5% in at least one part of area so as to obtain the composite coating.

18. The method of claim 17, wherein step (1) further comprises;

(1-a) roughening at least a part of the surface of the substrate; and

(1-b) forming the insulating layer on the surface subjected to the roughening treatment by explosion spraying or plasma spraying, the roughening treatment being performed by at least one of sand blasting, sanding and chemical etching in step (1),

in the step (2), the electrothermal alloy layer is formed by supersonic spraying or plasma spraying.

19. The method of claim 17, further comprising:

and forming a conductive coating on at least one part of the surface of the electrothermal alloy layer by arc spraying or cold spraying.