METHOD OF PRODUCTION OF A HEATING COMPONENT BY THERMAL SPRAY AND HEATING COMPONENT

Abstract

A heating component and method of producing a heating component. The heating component includes a coating system applied to a substrate; and a sealant applied as at least one of a continuous or closed layer over the coating system.

Claims

1. A heating component comprising: a coating system applied to a substrate; and an epoxy-type or polymeric sealant applied as at least one of a continuous or closed layer over the coating system, wherein the coating system comprises: a heater element formed over the substrate and comprising an electrically conductive material; and an insulation layer formed between the substrate and heater element and comprising an electrically insulating ceramic.

2. The heating component according to claim 1, wherein the coating system further comprises a conductive layer applied over the heater element for form contacts for an external power supply.

3. The heating component according to claim 1, wherein the sealant permeates the coating system to improve insulating properties of the insulation layer.

4. The heating component according to claim 1, wherein the coating system further comprises a bond layer formed over the substrate and the insulting layer in formed over the bond layer.

5. The heating component according to claim 1, wherein a thickness of the insulation layer is 50-300 ?m.

6. The heating component according to claim 1, wherein a thickness of the sealant above the coating system is 0.05-5.0 mm.

7. The heating component according to claim 1, wherein the coating system includes only one insulation layer.

8. A method for producing a heating component, the method comprising: applying a coating system to a substrate; and applying an epoxy-type or polymeric sealant over the coating system as at least one of a continuous or closed layer, wherein the coating system comprises: a heater element formed over the substrate and comprising an electrically conductive material; and an insulation layer formed between the substrate and heater element and comprising an electrically insulating ceramic; wherein the heater element and the ceramic insulation layer are applied by thermal spraying.

9. The method according to claim 8, wherein the coating system further comprises a conductive layer applied over the heater element for form contacts for an external power supply.

10. The method according to claim 8, wherein the sealant permeates the coating system to improve insulating properties of the insulation layer.

11. The method according to claim 8, wherein the sealant penetrates the coating system to improve dielectric properties of the insulation layer.

12. The method according to claim 8, wherein the coating system further comprises a bond layer formed on the substrate and the insulation layer is formed over the bond layer.

13. The method according to claim 8, wherein a thickness of the insulation layer is 50-300 ?m.

14. The method according to claim 8, wherein a sealant is applied to a thickness of 0.05-5.0 mm above the coating system.

15. The method according to claim 8, wherein the insulation layer is sprayed over the substrate and the heater element is sprayed onto the insulation layer.

16. The method according to claim 8, wherein a bond layer is applied over the substrate by thermal spraying, and the insulation layer applied over the bond layer.

17. The method according to claim 8, wherein the coating system includes only one insulation layer.

18. A heating component comprising: a coating system applied to a substrate; and an epoxy-type or polymeric sealant applied over the coating system, wherein the sealant permeates the coating system to improve insulating properties of the insulation layer, wherein a thickness of the sealant above the coating system is 0.1-1.0 mm, and wherein the coating system comprises: a heater element formed over the substrate and comprising an electrically conductive material; and only one insulation layer formed between the substrate and heater element and comprising an electrically insulating ceramic.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein:

[0027] FIG. 1 illustrates a known coating system forming a heating element;

[0028] FIG. 2 schematically illustrates a cross-section of a known coating system of a heating element; and

[0029] FIG. 3 schematically illustrates a cross-section of a coating system according to embodiments of a heating element.

DETAILED DESCRIPTION

[0030] The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present invention may be embodied in practice.

[0031] FIG. 3 illustrates an exemplary embodiment of a coating system 2 for forming a heating component on a substrate 21. In contrast to the prior art component depicted in FIG. 2, in this exemplary embodiment, insulation layer 14 of the known heating element is omitted from the coating system and a sealant 27 is used to cover the completed heating component. Thus, in the exemplary embodiment depicted in FIG. 3, coating system 2 is formed by an optional metallic bond coat 22, e.g., NiCr, pure Ni, CrN (with Cr content between 10 to 50% wt.), Ni.sub.5Al (with Al content between 3 to 20% wt.), pure Al, stainless steels or Inconel alloys, being thermal sprayed, e.g., via an atmospheric plasma spraying (APS), electric arc wire spraying (EAW), combustion spray (CS), cold gas spray (CGS) process, or similar process from a thermal spray gun, such as F4 MB-XL, SINPLEXPRO or TRIPLEXPRO-210 all from Oerlikon Metco, to a thickness of 10 to 50 ?m, and preferably a thickness of 20 to 30 ?m to improve adhesion of the heating component to a metal substrate 21 that is preferably made from steel, stainless steel or aluminum based alloys. An electrically insulating ceramic material 23, e.g., Al.sub.2O.sub.3, ZrO.sub.2, MgO or mixtures, is thermally sprayed onto substrate 21 or onto optional metallic bond coat 22, e.g., via APS, suspension plasma spray (SPS), high velocity oxygen fuel (HVOF), detonation spraying, combustion powder spray (flame spray) or similar process, to a thickness of 150-350 ?m, and preferably 250-300 ?m to electrically separate heating element 24 from substrate 21/bond layer 22. Heating element 24, which is formed by, e.g., via APS, EAW, CS or CGS, comprises an electrically conductive material layer, e.g., NiCr, pure Ni, CrN (with Cr content between 10 to 50% wt.), Ni.sub.5Al (with Al content between 3 to 20% wt.), pure Al, high chromium steels, Inconel alloys or conductive ceramics like TiB.sub.2 or TiO.sub.2, and is, in particular, a patterned electrically conductive layer that is preferably applied with a meander type layout. The width, length and thickness of the conductive meandering path of heating element 13 are designed to produce an electric resistance suitable to achieve the required total electric power of 2 to 8 kW at the given voltage of 350 to 850 V. By way of non-limiting example, for an electric vehicle battery, which can be understood to deliver power of 2-8 kW, heating element 13 can be suitably dimensioned with a width of 2-10 mm, a length of 500-1500 m and a thickness of 20-30 ?m.

[0032] Electrically conductive layer 26, e.g., a copper based alloy, is patterned at zones via, e.g., APS, EAW, CP, CW, CS, HVOF or other process, with a sufficient thickness of e.g., 120-200 ?m and preferably 150-165 ?m, to allow heating element 24 to be connected to an external power source (not shown), e.g., by soldering. However, in lieu of the insulation layer applied over the heating element in the known art, i.e., ceramic top insulation layer 15 in FIG. 2, a sealant layer 27 is applied over conductive layer 26 and heating element 24 of coating system 2. The sealant is applied in a liquid form by brushing, spraying or dispensing. This sealant can be, e.g., an epoxy-like sealant with low solvent content, such as METCOSEAL ERS from Oerlikon Metco or DICHTOL HM-RT or a polymeric sealant. The sealant is applied so that, depending upon the type of sealant, the sealant permeates, infiltrates and/or envelopes coating system 2 until a layer thickness above electrically insulating ceramic material 23 of greater than 0 (>0)-5.0 mm, preferably 0.01-1.0 mm, especially 0.05-0.15 mm, is achieved. However, the layer thickness is less than a sum of the thicknesses of conductive layer 26 and heating element 24 so that sealant layer 27 surrounds conductive layer 26, so that at least an upper portion of conductive layer 26 rises above the sealant layer 27. Moreover, by way of non-limiting example, the sealant layer 27 may be applied with a thickness that is at least 50 ?m greater than the thickness of heating element 24, and preferably 100 ?m greater than the thickness of heating element 24. Sealant layer 27 can be cured according to particular requirements of the sealant. However, an opening can be provided in the sealant in order for the external power source to access contacts for heater element 24 via electrically conductive layer 26.

[0033] The exemplary embodiment of the heating component in FIG. 3 utilizes only three or four layers, where the bond layer is optional, in which at least one of the layers and preferably all of the layers are thermally sprayed coating layers, yet provides improved insulation properties of insulation layer 23 due to improved sealing of insulation layer 23. Further, the exemplary embodiment is able to avoid the upper insulation layer 15 in the known art, i.e., above the heating element 14, because the sealant of sealant layer 27 penetrates the full coating system and thereby improves the electrically insulating properties of insulation layer 23 by increasing breakdown voltage and decreasing leakage currents. Moreover, these improved properties offered by the use of the sealant in sealant layer 27 allows the coating system to reduce the thickness of insulation layer 23 from 500 ?m, as in the known art, to 50-350 ?m, and preferably 150-300 ?m. Moreover, the sealant of sealant layer 27 can be applied in such an amount that sealant that cannot infiltrate or be contained by the coating system 2 will form a continuous film over coating system 2 that is electrically insulating. Sealant layer 27 can be applied onto insulation layer 23 (and over heating element 24) to at least a thickness of 50 ?m above, and preferably 100 ?m above, heating element 24. In this way, the thickness of sealant layer 27, which is preferably less than the sum of the thicknesses of conductive layer 26 and heating element 24, forms islands of conductive layer 26 rising above the surface of sealant layer 27. Further, the thickness of sealant layer 27 can be, e.g., greater than 0 (>0)-5.0 mm, and is preferably 0.01-1.0 mm, and more preferably 0.05-0.15 mm.

Embodiment 1

[0034] Coating system 2 is formed by applying insulation layer 23, heater element 24 and conductive layer 26, and optionally bond coat 22, by a thermal spray process, e.g., APS or other suitable thermal spray process. In areas where heating element 24 is to be connected to the power supply, covers are arranged to mask contact pads so that they are still accessible after the application of sealant layer 27. A 2-component epoxy-like sealant, e.g., METCOSEAL ERS from Oerlikon Metco or DICHTOL HM-RT can be applied in such a quantity that a closed liquid film of 0.1-1 mm is formed over coating system 2. As there is no top insulation layer 15 as in prior art to penetrate, more sealant from sealant layer 27 accesses the insulation layer 23, thereby improving the dielectric properties to separate the heating layer 24 and the substrate 21. In separate measurements, it was shown that, after applying the sealant of sealant layer 27, the discharge resistance of insulation layer 23, e.g., Al.sub.2O.sub.3, can be increased from about 5 kV/mm to up to 50 kV/mm. In view of this increase in discharge resistance, insulation layer 23 can be reduced in thickness by 50% to a minimum thickness of about 50 ?m without increasing the risk of short-circuiting heating element 24 to substrate 21.

[0035] The excessive sealant on top of the coating system 2 forms a hard, dense resin-like overlay forming an electrically insulating layer that is impermeable to humidity. This excessive sealant coating is what allows coating system 2 to dispense with the insulation layer over the heating element in the known art. The resin-like overlay can resist temperatures up to 300? C., which is sufficient for using the heating component on a water cooled heater. The resin-like coating also achieves better values in breakdown voltage than a thermal sprayed insulation coating, as the thermal sprayed insulation suffers from porosity and thin crack networks. Moreover, application of this epoxy-type sealant does not require sophisticated equipment and, unlike APS layers, there is no losses of material.

[0036] Further benefits can be achieved by applying vibrations to coating system 2 during the heat curing treatment to avoid enclosed air bubbles in the sealant, which can thereby avoid pin-holes that bear the risk of undesired discharge to other components above the heating element.

[0037] An even higher degree of penetration of the sealant can be achieved by vacuum impregnation. The component with the full coating system and masking of the contact pads is placed in a vacuum vessel above the sealant liquid. At low pressure or near vacuum conditions the component is placed into the resin and then the pressure is brought back to atmospheric pressure. The amount of excessive sealant on the surface must be adapted in a separate processing step by adding of removing sealant.

Embodiment 2

[0038] Insulation layer 23, heater element 24 and conductive layer 26 of coating system 2, and optionally bond coat 22, can be applied and masked as described in Embodiment 1. A one-component polymeric sealant can be applied in a manner similar to that described in Embodiment 1 so that excessive sealant forms a continuous overlay over the full surface of coating system 2. The thickness of this excessive sealant layer is in a range of 0.1-1 mm. This sealant requires a 6 hour drying period followed by heat treatment. While this sealant has a reduced capability to penetrate coating system 2, this sealant layer has very high electric insulating properties and thereby avoids effectively discharging and short-circuiting to nearby components. The formed overlay remains elastic and is resistant to a large number of liquid chemicals and is stable up to 500? C. before decomposing.

Embodiment 3

[0039] Insulation layer 23, heater element 24 and conductive layer 26, and optionally bond coat 22, of coating system 2 can be applied and masked as described in Embodiment 1. One of the sealants mentioned in Embodiment 1 and 2 can be applied on the full surface of coating system 2 in an amount so that excessive sealant forms a very thin film of up to 0.01-0.1 mm. A thin sheet of plastic that can withstand temperatures of 350? C. made from e.g., polyether ether ketone (PEEK), epoxy, glass, ceramic fiber (asbestos replacement), boron nitride, aluminum oxide, is placed on top of the excessive sealant film as a cover. The excessive sealant will act as an adhesive that bonds the cover smoothly to coating system 2, electrically insulates coating system 2 and protects coating system 2 from moisture pick-up and mechanical damage.

[0040] It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to an exemplary embodiment, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.