DE102017130806A1 - THERMAL SPRAYING OF MICROHOLE BALLS - Google Patents

Abstract

Methods are provided for forming an insulating coating by thermal spraying. In a variant, the method includes thermal spraying a jet stream having a maximum temperature greater than or equal to about 900 ° C to a substrate to form the insulating coating on the substrate. Thermal spraying may be a high velocity flame (HVOF) process. The jet stream comprises a plurality of hollow microspheres, which may comprise a metal, such as nickel or iron. The insulating coating thus formed has a thermal conductivity (K) less than or equal to about 200 mW / m · K at standard temperature and pressure conditions and may have a heat capacity (c) greater than or equal to about 100 kJ / m · K.

Description

INTRODUCTION

The following section provides background information for the present disclosure, which is not necessarily the prior art.

The present disclosure relates to methods of thermally injecting microcavity particles onto substrates to form insulating thermal barrier coatings.

Insulating and thermal barrier coatings are used in various applications to reduce heat transfer. Such coatings desirably have low heat capacity and low thermal conductivity. In certain aspects, a thermal barrier coating may include an insulating material that includes one or more hollow microspheres. Thus, the insulating or thermal barrier coating may be used in a variety of applications, including as a non-limiting example, on surfaces of components in an internal combustion engine to reduce heat transfer losses and increase power and efficiency. New methods for forming robust thermal barrier coatings on a variety of complex components are desirable.

SUMMARY

This part provides a general summary of the disclosure and is not a complete disclosure of the full scope or all features.

The present disclosure relates to thermal spray deposition of micro hollow structures, such as microspheres. In a variation, the present disclosure provides a method of making an insulating coating, including thermally spraying a jet stream having a maximum temperature greater than or equal to about 900 ° C, to a substrate to form the insulating coating on the substrate. The jet stream contains several hollow microspheres. The formed insulating coating has a thermal conductivity (K) less than or equal to about 200 mW / mK under standard temperature and pressure conditions.

In one aspect, the insulating coating includes multiple micro-hollow structures with intact void areas after thermal spraying.

In another aspect, the insulating coating has a net porosity greater than or equal to about 80% by volume.

In yet another aspect, the insulating coating has a thickness less than or equal to about 200 micrometers (μm).

In certain aspects, the jet stream has a maximum temperature less than or equal to about 1400 ° C.

In another aspect, the plurality of microspheres include a metal selected from the group consisting of: nickel, iron, combinations, and alloys thereof.

In further aspects, the plurality of microspheres include the metal in a first layer and further a second layer of a second metal selected from the group consisting of: copper, zinc, tin, nickel, and combinations thereof.

In yet another aspect, the substrate includes at least one metal selected from the group consisting of: nickel, iron, copper, zinc, aluminum, combinations, and alloys thereof.

In another aspect, the thermal conductivity (K) of the insulating coating is less than or equal to about 100 mW / m · K under normal standard temperature and pressure conditions.

In further aspects, a heat capacity (c _v ) of the insulating coating is less than or equal to about 100 kJ / m 3 · K.

In another variation, the present disclosure provides a method of forming an insulating coating, including injecting a stream including a plurality of hollow microspheres from a high velocity oxygen fuel (HVOF) device to a substrate. The stream includes the plurality of microspheres including a first metal layer having a first metal selected from the group consisting of: nickel, iron, combinations and alloys thereof, and a second metal layer having a second metal selected from the group consisting of: copper zinc , Tin, nickel, combinations and alloys thereof. Further, the current has a maximum temperature during injection that is at least about 50 ° C below a melting point of the first metal layer, but at or above a melting point of the second metal layer. The method also includes forming the insulating coating on the substrate having a thermal conductivity (K) less than or equal to about 200 mW / m-K at standard temperature and pressure.

In one aspect, the insulating coating includes multiple micro-hollow structures with intact void areas after thermal spraying.

In another aspect, the insulating coating has a net porosity greater than or equal to about 80% by volume.

In yet another aspect, the insulating coating has a thickness less than or equal to about 200 micrometers (μm).

In still other aspects, the insulating coating may have a thickness less than or equal to about 200 micrometers (μm)

In another aspect, the maximum temperature is greater than or equal to about 900 ° C, or less than or equal to about 1400 ° C.

In yet another aspect, the substrate includes at least one metal selected from the group consisting of: nickel, iron, copper, zinc, tin, nickel, aluminum, combinations and alloys thereof.

In other aspects, the substrate includes a first metal selected from the group consisting of: nickel, iron, combinations and alloys thereof, and further a second metal selected from the group consisting of: copper, zinc, tin, nickel, combinations and alloys thereof.

In still other aspects, the plurality of microspheres include the first metal layer with nickel and the second metal layer with copper.

In still other aspects, the thermal conductivity (K) at normal standard temperature and pressure conditions is less than or equal to about 100 mW / m · K.

In another aspect, the insulating coating has a heat capacity (c _v ) less than or equal to about 100 kJ / m ³ · K.

In yet another aspect, the method further includes sintering the insulating layer after injection.

In yet another variation, the present disclosure provides a method of forming an insulating coating that includes injecting a stream containing a plurality of hollow microspheres from a high velocity oxygen fuel (HVOF) device to a substrate about a layer of deposited microcavity structures to build. The stream has a maximum temperature during injection that is greater than or equal to about 900 ° C to less than or equal to about 1400 ° C. Each of the plurality of hollow microspheres includes a first metal layer and a second metal layer. The first metal layer comprises a first metal selected from the group consisting of: nickel, iron, combinations and alloys thereof and the second metal layer having a second metal selected from the group consisting of: copper, zinc, tin, nickel, combinations and alloys thereof on. The method further includes the sintering of the layer deposited micro hollow structures to form the insulating coating on the substrate having a thermal conductivity (K) is less than or equal to about 200 mW / m · K at standard temperature and pressure conditions, and a heat capacity (c _v) less than or equal to about 100 kJ / m ³ · K.

Other applications will be apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

list of figures

• 1 zeigt eine Hochgeschwindigkeits-Sauerstoffflamm (HVOF)-Thermospritzvorrichtung, die gemäß bestimmten Aspekten der vorliegenden Offenbarung zum Abscheiden von Mikrohohlkugeln zur Bildung einer isolierenden Beschichtung verwendet werden kann.
• 2 zeigt ein Beispiel einer Mikrohohlkugel mit einer einzelnen Metallschicht.
• 3 zeigt ein weiteres Beispiel einer Mikrohohlkugel mit zwei unterschiedlichen Metallschichten zur Verwendung in den thermischen Spritzverfahren gemäß bestimmten Aspekten der vorliegenden Offenbarung.
• 4 zeigt eine isolierende Beschichtung, einschließlich Mikrohohlstrukturen, die auf einem Substrat gemäß bestimmten Aspekten der vorliegenden Offenbarung über thermisches Spritzen abgeschieden werden.
• 5 zeigt eine Verbund-Wärmedämmschicht, einschließlich einer isolierenden Beschichtung, einschließlich Mikrohohlstrukturen, die auf einem Substrat gemäß bestimmten Aspekten der vorliegenden Offenbarung über thermisches Spritzen abgeschieden werden.

The drawings described herein are for illustration only of selected embodiments and are not intended to embody all of the possible implementations and are not intended to limit the scope of the present disclosure.

• 1 shows a high-speed oxygen flame (HVOF) thermal spray apparatus which may be used to deposit hollow microspheres to form an insulating coating in accordance with certain aspects of the present disclosure.
• 2 shows an example of a hollow microsphere with a single metal layer.
• 3 FIG. 12 shows another example of a hollow microsphere having two different metal layers for use in the thermal spray processes according to certain aspects of the present disclosure.
• 4 FIG. 12 shows an insulating coating, including micro-hollow structures, deposited on a substrate in accordance with certain aspects of the present disclosure via thermal spraying.
• 5 FIG. 12 shows a composite thermal barrier coating, including an insulating coating, including micro-hollow structures, deposited on a substrate in accordance with certain aspects of the present disclosure via thermal spraying.

Like reference numerals indicate similar construction portions throughout the several views of the drawings.

DETAILED DESCRIPTION

Exemplary embodiments are provided so that this disclosure will be thorough and fully convey the scope of those skilled in the art. Numerous specific details are set forth, such as examples of specific compositions, components, devices and methods described to provide a thorough understanding of embodiments of the present disclosure. Those skilled in the art will recognize that specific details may not be required, that exemplary embodiments may be embodied in many different forms, and that neither of the embodiments is to be construed to limit the scope of the disclosure. In some exemplary embodiments, well-known methods, well-known device structures, and well-known techniques are not described in detail.

The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting in any way. As used herein, the singular forms "a / a" and "the" may also include plurals, unless the context clearly precludes this. The terms "comprising", "comprising", "containing" and "having" are inclusive and therefore indicate the presence of the specified features, elements, compositions, steps, integers, acts, and / or components, but do not exclude the presence or adding one or more other features, integers, steps, acts, elements, components, and / or groups thereof. Although the term "includes" is to be understood as a non-limiting term used to describe and claim various embodiments set forth herein, in certain aspects the term may alternatively be construed as, for example, a more limiting and restrictive term be like "consisting of" or "consisting essentially of". Thus, any embodiment that presents compositions, materials, components, elements, functions, integers, operations, and / or method steps, expressly includes embodiments of the present disclosure consisting of, or consisting essentially of, compositions, materials, components, Elements, functions, numbers, operations and / or process steps. By "consisting of", the alternative embodiment excludes any additional compositions, materials, components, elements, functions, numbers, operations, and / or operations, while "consisting essentially of" excludes any additional compositions, materials, components, elements, functions , Numbers, operations and / or process steps, which materially affect the fundamental and novel properties are excluded from such an embodiment, but any compositions, materials, components, elements, functions, integers, operations and / or process steps, the material not the may affect basic and novel characteristics may be included in the embodiment.

All of the method steps, processes, and operations described herein are not to be construed as necessarily requiring the order described or illustrated, unless specifically stated as the order of execution. It should also be understood that additional or alternative steps may be used unless otherwise stated.

When a component, element or layer is described as being "on, on, in, engaged with, or coupled with" another component or element, it may either directly on / on the other component, the other element, or the other layer, in engagement with, connected to or coupled to, or there may be intervening elements or layers. Conversely, when an element is described as being "directly on," "directly engaged with," "directly connected to," or "directly coupled to" another element or layer, there may be no intervening elements or layers , Other words used to describe the relationship between elements are to be understood in the same way (eg, "between" and "directly between," "adjacent" and "directly adjacent," etc.) As used herein, The term "and / or" includes all combinations of one or more of the associated listed items.

Although the terms first, second, third, etc., may be used herein to describe various steps, elements, components, regions, layers, and / or sections, these steps, elements, components, regions, layers, and / or sections are not intended to be these expressions are restricted. These terms are only used to distinguish one step, item, component, region, layer, or section from another step, another element, another region, another layer, or another section. Terms, such as "first,""second," and other numerical terms, when used herein, do not imply any sequence or order unless this becomes so clearly indicated by the context. Thus, a first step, element, component, region, layer, or section, discussed below, could be termed a second step, element, component, region, layer, or section without departing from the teachings of the exemplary embodiments departing.

Spatial or time related terms, such as "before", "after", "inner", "outer", "below", "below", "lower", "above", "upper", and the like, may be used herein to better describe Relationship of an element or a property to other element (s) or property (s), as shown in the figures, are used. Spatial or time related terms may be intended to rewrite various device or system deployments in use or in operation, in addition to the orientation shown in the figures.

In this disclosure, the numerical values basically represent approximate measurements or boundaries of ranges, such as minor deviations from the particular values and embodiments having approximately the stated value, as well as those having exactly that value. In contrast to the application examples provided at the end of the detailed description, all numerical values of the parameters (eg, sizes or conditions) in this specification, including the appended claims, are to be understood in all instances by the term "about," whether or not "Approximately" actually appears before the numerical value. "Approximately" indicates that the disclosed numerical value allows for some inaccuracy (with some approximation to accuracy in value, approximately or realistically close to value, approximately). If the inaccuracy provided by "about" is not otherwise understood by those of ordinary skill in the art to be ordinary, then "about" as used herein will at least indicate variations resulting from ordinary measurement techniques and the use of such parameters. For example, "about" may be a variation of less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less may be equal to or greater than 0.5% and, in certain aspects, may be less than or equal to 0.1%.

In addition, the disclosure of areas involves the disclosure of all values and further subdivided areas within the entire area, including the endpoints and subareas specified for the areas.

Exemplary embodiments will now be described in more detail with reference to the accompanying drawings.

In various aspects, the present disclosure describes methods of forming an insulating coating on a substrate. In certain aspects, the method may include thermal spraying a jet stream onto a substrate. Thermal spraying means that a method is used wherein a precursor material is heated and propelled as a single particle on a surface of the substrate to form a robust and continuous coating. Thermal spraying thus relies on heat and momentum to cause the coating material to conform to and bond to the surface to be coated.

In certain aspects, the thermal spray process has a maximum temperature greater than or equal to about 900 ° C, optionally greater than or equal to about 1000 ° C, optionally greater than or equal to about 1100 ° C, and in certain aspects optionally greater than or equal to about 1200 ° C , In certain aspects, the thermal spray process has a temperature greater than or equal to about 900 ° C to less than or equal to about 1400 ° C, and in certain variations optionally greater than or equal to about 1100 ° C to less than or equal to about 1200 ° C. As will be apparent to those skilled in the art, some cooling occurs as the sprayed material exits the thermal spray gun so that the temperature in the thermal spray device is desirably high enough to promote the softening or melting of at least one material in a hollow precursor. while avoiding overheating which could cause structural break-in, as further described below.

In all thermal spray coating processes, material is heated, accelerated and shot at a target surface. Particle velocities vary in different thermal spray processes, for example jet velocities are highest in high velocity flame processes and lower in low velocity spray processes, such as subsonic oxygen powder processes. A jet stream means that the stream has a relatively high velocity and produces a jet while still desirably avoiding velocities, the burglary of a hollow precursor under the selected conditions during thermal spraying (eg, selecting temperatures and pressures). would promote. For example, a maximum velocity of a jet stream is for use in accordance with certain aspects of the present invention Revelation less than or equal to about 400 m / s, optionally less than or equal to about 100 m / s and in certain aspects optionally less than or equal to about 10 m / s. In certain variations, the jet stream may have a supersonic velocity greater than about 343 m / s, but less than or equal to about 400 m / s.

In the high-speed flame coating method, the gas flow is generated by mixing and igniting oxygen and fuel (gas or liquid) in a combustion chamber and accelerating the high-pressure gas through a nozzle. Microparticles are introduced into this stream where they are heated and accelerated to a target surface. In a variation according to certain aspects of the present disclosure, a method of forming an insulating coating in FIG 1 shown injecting a stream, the plurality of microcavities or microspheres 102 from a high speed oxygen fuel (HVOF) device 100 on a substrate 110 includes. The micro-hollow particles define an enclosed cavity area in the core, which may be filled with an insulating material. Thus, the cavity portion in the core may be filled with, for example, a gas such as air or an inert gas, or may have vacuum conditions. In certain aspects, the microparticles have at least one spatial dimension that is less than about 100 microns, optionally less than or equal to about 50 microns, and in certain aspects, less than or equal to about 10 microns.

The microparticles may be microspheres having a substantially round shape. "Substantially round" includes microparticles having a shape that is spherical, spherical, ellipsoidal, disc-shaped, cylindrical, dome-shaped, egg-shaped, elliptical, orbital, oval, and the like as long as at least a portion of the center of the microparticles defines an enclosed void area. Thus, the reference herein to microspheres may include any of these substantially circular shapes. While the precursor may be a microsphere, after the thermal spray process, the microsphere may be distorted from a spherical or substantially circular shape.

In certain aspects, the microspheres used as a precursor during thermal spraying may have an average particle diameter less than about 100 microns (μm), optionally greater than or equal to about 10 μm to less than or equal to about 80 μm, optionally greater than or equal to about 20 microns to less than or equal to about 60 microns and in certain variations optionally greater than or equal to about 30 microns to less than or equal to about 40 microns. It should be noted that the microspheres have a mean diameter within these ranges, but the plurality of microspheres do not necessarily all have the same diameter since a mixture of different diameter microspheres can be used to provide a desired porosity or packing density the thickness may vary within the formed insulating coating. It should also be noted that the smaller the diameter of the microspheres used, the greater the particle density and therefore the mass of the coating formed from such particles. Thus, relatively large microspheres form lighter coatings than smaller microspheres.

The plurality of microspheres comprises at least one metal. In certain variations, the metal is selected from the group consisting of: nickel, iron, combinations and alloys thereof. In one variation, the metal is nickel or a nickel alloy. In another variation, the metal may include iron and microspheres may include an iron alloy such as steel or stainless steel. Each alloy may contain additional elements, as recognized by those skilled in the art, such as carbon, manganese, chromium and nickel, molybdenum, and the like, as a non-limiting example.

In general, hollow microspheres 20 , such as the in 2 shown, a structural material 22 include the enclosed cavity area 24 Are defined. The structural material 22 may be selected from the group consisting of: metal, glass, ceramics, polymers and combinations thereof, as long as the structural material 24 a hollow structure with the enclosed cavity area 24 Are defined. The hollow microspheres 20 may then be coated with one or more conductive materials, such as metals such as nickel, iron, nickel alloy compounds, iron alloy compounds, and the like. A metal coating 26 is thus about the structural material 22 educated. The application of the metal on the surface of the microspheres 20 can be carried out by a method such as electroplating, vapor deposition, electroless plating, flame spraying, painting and the like. The microsphere 20 may be used in thermal spraying, but in certain aspects will be used as a precursor to form a multi-layered hollow microspheres, as in U.S. Pat 3 shown used.

In 3 can be a micro hollow sphere 30 , which is used as a precursor in the thermal spraying method according to certain aspects of the present disclosure, have a plurality of different metal layers. In a variation, the hollow microspheres 30 a structural material 32 on, that is a cavity area 34 in the middle core area Are defined. The structural material 32 can be made of the same materials as the above structural material 22 be formed. A first metallic material comprising a first metal may be applied to the surface of the structural material 32 are applied to form a first metal layer or coating 36. A second metallic material may comprise a second different metal overlying the first metal coating 36 may be applied to form a second metal layer or coating 38.

The first metal coating 36 may include nickel, iron, combinations and alloys thereof. In certain aspects, the first metal coating comprises 36 Nickel or a nickel alloy. The second metal coating 38 may include copper, zinc, tin, nickel, combinations and alloys thereof. While the first metal coating 36 and the second metal coating 38 contain one or more of the same metals, each layer / coating has a specific composition and thus different melting points. In certain aspects, the second metal coating comprises 38 Copper or a copper alloy. In other aspects, the second metal coating may 38 a combination of copper and zinc, for example a brass alloy. In certain aspects, a brass alloy has zinc in the composition of less than or equal to about 32% by weight (to avoid the formation of undesirable phases) while the remainder may contain copper and impurities. In this way, the first metal coating 36 and the second different metal coating 38 different melting point temperatures, which may be advantageous for certain thermal spray processes, as further described below. In particular, the first metal layer or coating 36 may have a higher melting point than the second metal layer or coating 38. Thus, the second metal coating 38 may include, in certain variations, copper and nickel with nickel in the composition up to about 30% by weight and the remainder copper and impurities. In other aspects, the second metal coating may 38 Include nickel and tin, wherein tin is present in the composition up to about 30 wt .-% and the balance is nickel and impurities. Such a nickel-tin alloy has a low melting point / eutectic point of about 1130 ° C. In certain further aspects, the second metal coating may 38 Include nickel and zinc, wherein zinc is present in the composition up to about 40 wt .-% and the balance is nickel and impurities.

In certain aspects, the first metal coating 36 have a thickness of about 1 micron while the second metal coating 38 a thickness may be less than or equal to about 1 micron. Thus, the thickness of the second metal layer or coating 38 is less than the thickness of the first metal layer or coating 36. When the first metal coating 36 Nickel and the second metal coating 38 Copper, the copper can diffuse into the nickel. The more copper from the second metal coating 38 in the first metal coating 36 diffuses, the lower the maximum temperature that can be used during thermal spraying while maintaining the hollow structures (eg, the first metal coating 36 as a hollow form remains structurally intact, especially when the structural material 32 from the hollow microsphere 30 has been removed). However, most diffusion of copper into nickel occurs after the thermal spray process when a subsequent heat treatment (eg, for sintering) is performed. The final alloy composition (the Ni-Cu alloy) can potentially limit a maximum end use temperature (eg, as a thermal insulation material in an engine).

With renewed reference to 1 The HVOF process uses combustion to generate heat and give velocity to the jet stream. The HVOF device 100 includes two fuel inlets 120 for a fuel stream and two oxidant inlets 122 for introducing an oxygen-containing stream (or other oxygen-containing streams). It should be noted that the fuel inlets 120 and oxidant inlets 122 are not limited to the number of entrances or the arrangement in 3 are shown. The fuel may include propane, propylene and / or hydrogen as a non-limiting example. Further, although not shown, cooling inlets and channels circulating a coolant may also be provided. A central inlet 130 receives a stream of carrier gas and the plurality of hollow microspheres 102 that are inflated in it. The carrier gas may, by way of non-limiting example, be an inert gas, such as nitrogen and / or argon, or the carrier gas may have the same composition as the oxygen-containing stream or fuel stream. In certain alternative constructions, not shown, the central inlet could 130 may be omitted or modified so that the hollow microspheres are introduced directly into the fuel stream (s) or oxidant stream (s).

In the HVOF device 100 The oxygen-containing stream and the fuel combine in a mixed area 132 , The mixed stream is in a combustion chamber 134 introduced, in which an exothermic combustion reaction takes place. The Carrier gas and the hollow microspheres 102 arrive in and through the combustion chamber 134 in which they are heated and then into a nozzle 136 penetration. A beam current 140 high temperature and high speed comes out of the nozzle 136 out. The beam current 140 may be a supersonic spray flame in certain variations. The operating parameters for the HVOF device 100 are selected in accordance with certain aspects of the present disclosure to promote softening, adherence, and bonding of the microspheres to the substrate while minimizing break-in or tearing of the interior void areas.

For example, in certain aspects, a maximum temperature of the jet stream 140 (and within the HVOF device 100 ) is selected to be at least about 50 ° C below a melting point of a selected metal forming the hollow microspheres 102, for example a first metal in the first metal layer / coating. Thus, in certain aspects, when the metal is nickel, a maximum temperature is at least 50 ° C below the melting temperature of 1455 ° C nickel, so that a maximum HVOF process and jet stream temperature is less than about 1405 ° C (or about 1400 ° C ). In certain variations, throughout the process, the stream (and microspheres) encounters a maximum injection temperature that is greater than or equal to about 900 ° C to less than or equal to about 1400 ° C; optionally greater than or equal to about 1000 ° C to less than or equal to about 1300 ° C, and in certain aspects optionally greater than or equal to about 1100 ° C to less than or equal to about 1200 ° C. The operating temperature and pressures used in the HVOF can be tuned to enable the deposition of various microspheres, such as those comprising nickel or iron (eg, steel or stainless steel) microspheres, on a surface. without melting at least one layer of the microspheres. By using HVOF and other similar thermal spray technologies, hollow microspheres can be rapidly deposited on surfaces. The temperatures in the sprayer and the microspheres can be adjusted so that the microspheres do not break but develop a first bond upon impact with a surface of the target substrate.

In certain variations, where a first metal is present in a first layer together with a second metal as part of a second layer of hollow microspheres, the HVOF maximum temperature may be at least 50 ° C below the melting point of the first metal but may be Reach or exceed the melting point of the second metal on the outer coating. The second metal layer and / or second layer is thus softened and partially or completely melted to improve adhesion and bonding when the hollow microspheres are on the substrate 110 be deposited. Thus, in certain variations, the first metal may be nickel with a melting point of about 1455 ° C and the second metal copper with a melting point of about 1084 ° C such that the maximum temperature of the jet stream is below the melting point of nickel but above the melting point of copper can lie. In such variation, the maximum temperature may be greater than or equal to about 1110 ° C to less than or equal to about 1400 ° C. For example, the temperature of the jet stream may be above the copper melting point of about 1084 ° C when the microspheres strike the target but do not reach the maximum temperature during thermal spraying 1455 ° C (the melting point of nickel). Specifically, the microcavities cool somewhat as they exit the gun so that higher maximum temperatures in the gun thermal sprayer can exceed 1100 ° C and cool as the microbubbles approach and contact the target. When the second layer comprises copper and zinc, the melting point temperature is lower. For example, a brass alloy comprising copper and about 32% by weight of zinc has a melting point of about 903 ° C, so that the above thermal spraying temperatures can be adjusted accordingly. The temperature of the jet stream may be near or above the melting point of the brass alloy of about 903 ° C when the microspheres strike the target, however, the maximum jet stream temperature during thermal spraying remains below 1455 ° C (the melting point of nickel).

The beam current is applied to a surface of the substrate 110 directed, where several micro hollow structures 142 in a cohesive insulating coating 144 is deposited with high porosity. The substrate may be formed from a variety of materials that can withstand high temperatures, including metals, ceramics, and the like. In certain aspects, the substrate comprises at least one metal selected from: nickel, iron, copper, zinc, tin, aluminum, magnesium, combinations and alloys thereof. The substrate may include, in certain variations, steel, superalloys such as Inconel nickel superalloys, aluminum alloys, and magnesium alloys, as a non-limiting example.

The substrate 110 may comprise a coating or be formed of a material that promotes the adhesion of the micro-hollow structures. The surface may comprise at least one metal selected from: copper, zinc, tin, nickel, aluminum, combinations and alloys thereof. The Surface may have a metallic surface coating or may be formed from a metal comprising copper and / or zinc and / or their alloys. The coating comprising copper and / or zinc may be applied to any heat-resistant substrate by electroplating, electroless plating, vapor deposition, flame spraying, painting and the like. In a variation, the substrate may be 110 be formed of a copper-containing material or may comprise a copper-containing coating. If the substrate 110 As a non-limiting example, the substrate may comprise any type of refractory material, including steel, superalloys such as Inconel nickel superalloys.

The resulting thermal spray coating comprises adjacent and / or overlapping micro hollow structures. After thermal spraying on the substrate 110 shows an essential section of the micro hollow structures 142 For example, more than about 80% of the micro-hollow structures may have intact voids, optionally more than about 90%, optionally more than about 95%, optionally more than about 97%, and in some aspects optionally more than about 98 % of the voids within the micro hollow structures after deposition intact. In certain variations, the deposited micro hollow structures may 142 the same microsphere shape as that in the HVOF device 100 However, it is also possible that they may deform or distort into other forms.

Accordingly, the deposited microparticles may have some shape distortion after thermal spraying, but desirably maintain an internal trapped cavity area, thereby enhancing and maintaining the insulating properties of the deposited coating. As such, an insulating coating comprises 200 on a substrate 210 by thermal spraying, as in 4 is shown formed micro hollow structures (formed by deposition of the microspheres) with intact cavity areas. The insulating coating with such micro hollow structures desirably has a thermal conductivity (K) less than or equal to about 1000 mW / mK at standard temperature and pressure conditions, optionally less than or equal to about 500 mW / mK, less than or equal to about 250 mW / m · K, optionally less than or equal to about 200 mW / m · K, optionally less than or equal to about 100 mW / m · K, optionally less than or equal to about 50 mW / m · K, and possibly smaller in certain variations than or equal to about 20 mW / m · K. Standard temperature and pressure conditions are about 32 ° F or 0 ° C and an absolute pressure of about 1 atm or 100 kPa.

Further, the insulating coating having such micro hollow structures desirably has a heat capacity (c _v - volumetric heat capacity) equal to or less than about 5000 kJ / m ³ · K, optionally less than or equal to about 1000 kJ / m ³ · K, optionally less than or equal to about 500 kJ / m ³ · K, optionally less than or equal to about 100 kJ / m ³ · K, and in certain variations optionally less than or equal to about 50 kJ / m ³ · K. In one variation, the insulating coating has a thermal conductivity (K) less than or equal to about 100 mW / m · K and a heat capacity (c _v ) less than or equal to about 100 kJ / m ³ · K.

The insulating coating 200 that is deposited by thermal spraying, such as HVOF, can form densely packed micro-hollow structures 212 exhibit. In certain aspects, the insulating coating comprises 200 containing several micro hollow structures 212 which are deposited by thermal spraying (eg, HVOF deposition) has a high open porosity, for example, with a net porosity of greater than or equal to about 80% by volume of the total volume of the coating. Net porosity means that a total porosity volume includes both a volume of voids within the nanostructures and a volume of voids defined between nanostructures. In certain variations, such net porosity is greater than or equal to about 85% by volume, optionally greater than or equal to about 90% by volume, and in certain variations optionally greater than or equal to about 95% by volume.

In certain variations, the insulating coating can 200 an average thickness less than or equal to about 4000 microns ( 4 μm), optionally less than or equal to about 2000 microns ( 2 μm), optionally less than or equal to about 1000 micrometers ( 1 microns), optionally less than or equal to about 500 microns, optionally less than or equal to about 400 microns, optionally less than or equal to about 300 microns, optionally less than or equal to about 200 microns, optionally less than or equal to about 100 microns, optionally smaller at or about 75 microns, and optionally in certain variations, less than or equal to about 50 microns. In certain aspects, an average thickness of the insulating coating is 200 greater than or equal to about 100 microns to less than or equal to about 4000 microns, optionally greater than or equal to about 100 microns to less than or equal to about 500 microns, optionally greater than or equal to about 100 microns to less than or equal to about 300 microns. In one variation, the insulating coating has a thickness less than or equal to about 200 microns (μm). It It should be noted that the desired thickness of the coating may depend on the application in which the insulating coating is used, so that a thicker coating and / or higher mass coating may be suitable in applications where a slower thermal response is acceptable. while a thinner coating or lighter coating can be selected if faster thermal reactions are desired.

In certain aspects, the insulating layer is 200 capable of withstanding pressures greater than or equal to about 8 MPa, optionally greater than or equal to about 10 MPa, optionally greater than or equal to about 15 MPa, and in certain aspects greater than or equal to about 20 MPa without failure. In terms of high temperature performance, the insulating layer is, in certain variations, configured to have surface temperatures greater than or equal to about 200 ° C, optionally greater than or equal to about 250 ° C, optionally greater than or equal to about 300 ° C, optionally greater than or equal to about 500 ° C, optionally greater than or equal to about 700 ° C, optionally greater than or equal to about 1000 ° C and optionally greater than or equal to about 1300 ° C without failure. The heat capacity can ensure that the surface of the substrate 210 on which the coating 200 is arranged, for example, does not rise above about 250 ° C.

As will be apparent to those skilled in the art, the insulating layer may 200 actually several microstructures 212 having different compositions, sizes or shapes. Such microstructures may be mixed together during thermal spraying or superimposed successively as distinct layers (eg, different composition layers within the insulating coating).

With renewed reference to 1 In some aspects, thermal spraying may optionally be performed at ambient conditions or at a pressure greater than or equal to about 0.5 MPa. If in this way a positive pressure in the vicinity of the jet stream 140 and near the substrate 110 is applied, the volume expansion and contraction due to temperature changes of the hollow microspheres 102 and / or the deposited micro hollow structures 142 be suppressed and minimized while the pressure is increased.

In certain alternative aspects, the deposited microparticles may be cooled to ambient conditions after thermal spraying and then further processed. The micro hollow structures 212 For example, in the insulating coating 200 be further heat treated to promote additional bonding and sintering to improve the stability of the coating. An exemplary heating method for sintering may include heating an applied layer of microspheres on the substrate (having both a first metal in a first layer and a second metal in a second layer) to a temperature below the solidus temperature of the second metal. The second metal layer may comprise, for example, a Cu or a Cu-Zn alloy. Pure Cu can thus be heated to below 1084 ° C (copper solidus temperature) while a Cu-Zn alloy having less than 32 wt% Zn can be heated to below about 900 ° C. In one example, sintering may be performed at a temperature of about 800 ° C in an inert atmosphere, such as argon. The heat treatment for sintering may be more than or equal to about 1 hour, optionally for greater than or equal to about 2 hours, optionally for greater than or equal to about 4 hours, optionally for greater than or equal to about 6 hours, and in certain variations more or equal about 8 hours. In a further variation, the temperature may be slowly increased above the melting temperature of the second metal (eg, Cu), provided that the second metal diffuses into the first metal layer (eg, Ni), where the alloy containing both the first metal as well as the second metal, has a higher melting temperature than the second metal alone.

Further, after deposition, additional layers may be over the insulating coating 200 are deposited, for example ceramics, nickel, vanadium, molybdenum or other high-temperature metals.

In certain variations, the substrate may be formed from a substrate which may have lower heat resistance, such as aluminum, which typically is not heated to temperatures above 800 ° C. In such an application, a surface coating may be disposed on the surface of the aluminum and the deposited microparticles may be disposed on the surface coating. The deposited microparticles can be heated from an outside while the aluminum substrate itself remains cool. Alternatively, an intermediate substrate, such as a graphite nickel-plated nickel wafer, may be used. The micro-hollow particles are applied to the nickel wafer and then sintered. These materials can be added to a mold, and the aluminum or other cryogenic alloy can therefore be cast. Yet another variation is the use of an intermediate substrate, such as the nickel wafer described above. The micro hollow particles are deposited on the nickel Wafer applied and then sintered. The low-temperature substrate may have a surface coating as a bonding layer, for example, an aluminum substrate may have a copper and / or zinc surface coating for a bonding layer. The wafer with sintered micro hollow particles can then be sintered to the piston. This secondary sintering temperature is much lower than the initial sintering temperature for the micro-cellular particles (eg, comprising nickel). Thus, the substrate may optionally comprise a nickel-containing or iron-containing sealant layer, and this sealant layer could also have a fine copper or copper and nickel coating to promote bonding.

In a variation, the insulating coating may be in a composite thermal insulation arrangement 250 be integrated as in 5 shown. A thermal barrier coating 260 is on a substrate 262 arranged to the thermal insulation composite arrangement 250 , In a non-limiting embodiment, the substrate may be 262 Any type of refractory materials, including steel, include superalloys such as Inconel nickel superalloys, aluminum alloys, and magnesium alloys, as a non-limiting example.

The thermal barrier coating 260 includes several layers (and can have more than 3 layers than the ones in 5 have shown). An optional first layer 264 (if used) is a tie layer that is on a surface of the substrate 262 is arranged. A second layer 270 FIG. 12 is an insulating layer that includes a plurality of micro-hollow structures formed in accordance with certain aspects of the present disclosure. The first shift 264 facilitates bonding of the substrate 262 and the second layer 270. A third layer 272 that over the second layer 270 is arranged, serves as a sealing layer over the second layer 270 is arranged. The third layer may be a thin film configured to withstand the high temperatures and serves as a sealing layer that is impermeable to gases and has a smooth surface.

The optional first layer 264 which serves as a bonding layer may be formed of a metal comprising copper or zinc which is bonded to the surface of the substrate 262 and the second layer deposited thereon 270 diffuse and connect by any of the techniques described above. In a variation, the first layer 264 may comprise brass, which is a copper-zinc (Cu-Zn) alloy material. If the substrate 262 Aluminum is and the microspheres include nickel and / or iron, may be in a variation of copper and zinc to be included in the first layer 264 to be selected. Both copper and zinc show good solubility in aluminum, nickel and iron, while iron and nickel have very low solubility in aluminum. The first layer comprising a copper and zinc alloy may be used on aluminum substrates such as aluminum-containing pistons. Substrates made of steel or Inconel, such as valves, may be an optional first layer 264 for joining, for joining the second layer 270 although such a tie layer need not be necessary for these substrates. Thus, a first layer 264 with copper and / or zinc sees an interstructure layer between the substrate 262 and the second layer 270 to promote diffusion bonding between the aluminum substrate and nickel or iron microstructures. It should be noted, however, that the substrate 262 , the first layer 264 and the second layer 270 are not limited to aluminum, nickel, iron and brass, but may include other materials.

The third layer 272 serves as the sealing layer overlying the insulating second layer 270 is arranged. The sealing third layer 272 may be a high temperature thin film that may be configured to withstand temperatures of at least 1100 ° C. The third layer 272 may have a thickness less than or equal to about 20 microns, optionally less than or equal to about 5 microns, optionally less than or equal to about 1 micron. The third layer 272 is impermeable to gases such as combustion gases. In this way, the third layer serves 272 as a seal over the second layer 270 , Such sealing prevents dirt from combustion gases, such as unburned hydrocarbons, soot, partially reacted fuel, liquid fuel, and the like, from penetrating into the openings and pores existing between the micro-hollow structures in the second layer 270 are defined. Minimizing such deposits prevents gas within the pores from being displaced by the deposits, which could result in the insulating properties being reduced or eliminated. The third layer 272 may have a smooth outer surface that can prevent the generation of turbulent airflow as the air flows. Furthermore, a third layer 272 with a smooth surface to prevent increased heat transfer coefficient. As an example and not by way of limitation, the third layer may be on top of the second layer 270 (after thermal spraying and cooling) by electroplating, vapor deposition or other application techniques are applied. In a variation, the third layer includes 272 a heat-resistant or corrosion-resistant material. In a variation, the third layer 272 Molybdenum or vanadium include. The third layer 272 is configured to be sufficiently resilient to resist breakage or cracking during exposure to combustion gases, thermal fatigue, or debris. Further, the third layer 272 configured to be sufficiently compliant to any extent and / or contraction of the underlying insulating second layer 270 withstand. The third layer 272 may contain multiple layers.

A thermal insulation composite arrangement 250 can be used in a variety of applications, such as thermal insulation to components within an internal combustion engine. The thermal insulation composite arrangement 250 can be arranged on a surface or on surfaces of one or more of the components of an engine, for example on a piston, an intake valve, an exhaust valve, inner walls of an exhaust manifold and a combustion dome, as a non-limiting example. The thermal insulation composite arrangement 250 ideally has a low thermal conductivity to reduce heat transfer losses and low heat capacity, so that the surface temperature of the composite thermal insulation arrangement 250 the gas temperature in the combustion chamber follows. Thus, the thermal insulation composite arrangement allows 250 in that surface temperatures of the component oscillate with the gas temperatures. This reduces heat transfer losses without affecting the braking performance of the engine and without causing knocking. Furthermore, the heating of cold air entering the cylinder of the engine is reduced. In addition, the exhaust gas temperature is increased, resulting in a faster catalyst off-time and improved catalyst activity.

While the methods described herein are particularly suitable for use in components of automobiles or other vehicles, they may also be used in a variety of other industries and applications, including aerospace components, consumer goods, office equipment and furniture, industrial equipment and machinery, agricultural machinery or heavy machinery, to name just a few non-limiting examples. Non-limiting examples of vehicles that may include components manufactured according to certain aspects of the present disclosure include automobiles, trains, heavy mobile equipment, tractors, buses, motorcycles, boats, campers, campers, manned and unmanned aircraft, and tanks ,

The methods and insulating coatings described herein provide low thermal conductivity and low heat capacity thermal barrier coatings. Such thermal barrier coatings can improve fuel economy and emissions of internal combustion engines, increase operating temperatures, reduce post-heat warm-up time, and improve heat recovery. The deposition processes provide the ability to deposit microspheres on contours and various surfaces of complex parts, which otherwise may not be possible. The insulating coatings formed by such thermal spray processes exhibit only a relatively small reduction compared to insulating coatings formed from microspheres provided in a binder matrix that is cured or in microspheres that are sintered. Furthermore, it is believed that the insulating coatings formed by the thermal spray processes have increased adhesion to the underlying substrate as compared to other methods of applying microspheres.

The foregoing description of the embodiments is merely illustrative and descriptive. It is not exhaustive and is not intended to limit the revelation in any way. Individual elements or features of a particular embodiment are generally not limited to this particular embodiment, but may be interchangeable and optionally usable in a selected embodiment, although not separately illustrated or described. Also various variations are conceivable. These variations are not deviations from the disclosure, and all modifications of this nature are part of the disclosure and are within its scope.

Claims (10)

A method of forming an insulating coating comprising: injecting a stream comprising a plurality of hollow microspheres from a high velocity oxygen fuel (HVOF) device to a substrate, each of the plurality of hollow microspheres comprising a first metal layer comprising a first metal selected from the group consisting of: nickel, iron, Combinations and alloys thereof and comprising a second metal layer comprising a second metal selected from the group consisting of: copper, zinc, tin, nickel, combinations and alloys thereof, wherein the current during injection has a maximum temperature of at least about 50 ° C is below a melting point of the first metal but is greater than or equal to a melting point of the second layer; and forming the insulating coating on the substrate having a thermal conductivity (K) less than or equal to about 200 mW / m · K at standard temperature and pressure conditions. Method according to Claim 1 wherein the insulating coating comprises a plurality of micro hollow structures with intact void areas after thermal spraying. Method according to Claim 1 wherein the insulating coating has a net porosity greater than or equal to about 80% by volume and the insulating coating has a thickness less than or equal to about 200 microns (μm). Method according to Claim 1 wherein the maximum temperature is greater than or equal to about 900 ° C or less than or equal to about 1400 ° C. Method according to Claim 1 wherein the substrate comprises at least one metal selected from the group consisting of: iron, copper, zinc, tin, nickel, aluminum, combinations and alloys thereof. Method according to Claim 1 wherein the first metal layer comprises nickel and the second metal layer comprises copper. Method according to Claim 1 wherein the thermal conductivity (K) is less than or equal to about 100 mW / m · K. Method according to Claim 1 wherein the insulating coating has a heat capacity (c _v ) less than or equal to about 100 kJ / m ³ · K. Method according to Claim 1 further comprising sintering the insulating coating after injection. A method of forming an insulating coating, comprising: injecting a stream comprising a plurality of hollow microspheres comprising nickel from a high velocity oxygen fuel (HVOF) device to a substrate to form a layer of deposited microcavities, the stream having a maximum temperature during injection greater than or equal to about 900 ° C to less than or equal to about 1400 ° C, each of the plurality of hollow microspheres comprising a first metal layer comprising a first metal selected from the group consisting of: nickel, iron, combinations and alloys thereof and a second metal layer comprising a second metal selected from the group consisting of: copper, zinc, tin, nickel, combinations and alloys thereof; and sintering the layer of deposited microcavity structures to form the insulating coating on the substrate having a thermal conductivity (K) less than or equal to about 200 mW / m · K at standard temperature and pressure conditions and a heat capacity (c _v ) less than or equal to about 100 kJ / m ³ · K.

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