WO2008044128A2 - Innovative technique for improving the dielectric and anticorrosion characteristics of coatings obtained with thermal spray, aps, hvof and analogous technologies, in particular insulating coats such as al2o3 - Google Patents

Innovative technique for improving the dielectric and anticorrosion characteristics of coatings obtained with thermal spray, aps, hvof and analogous technologies, in particular insulating coats such as al2o3 Download PDF

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Publication number
WO2008044128A2
WO2008044128A2 PCT/IB2007/003028 IB2007003028W WO2008044128A2 WO 2008044128 A2 WO2008044128 A2 WO 2008044128A2 IB 2007003028 W IB2007003028 W IB 2007003028W WO 2008044128 A2 WO2008044128 A2 WO 2008044128A2
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WO
WIPO (PCT)
Prior art keywords
aps
hvof
technique
layer
similar
Prior art date
Application number
PCT/IB2007/003028
Other languages
French (fr)
Other versions
WO2008044128A3 (en
Inventor
Gianfranco Cirri
Maria Prudenziati
Original Assignee
Inglass S.P.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Inglass S.P.A. filed Critical Inglass S.P.A.
Publication of WO2008044128A2 publication Critical patent/WO2008044128A2/en
Publication of WO2008044128A3 publication Critical patent/WO2008044128A3/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
    • C23C28/34—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates
    • C23C28/345—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates with at least one oxide layer
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/04—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
    • C23C28/32—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer
    • C23C28/322—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer only coatings of metal elements only
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
    • C23C4/10—Oxides, borides, carbides, nitrides or silicides; Mixtures thereof
    • C23C4/11—Oxides
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C23C4/18—After-treatment

Definitions

  • thermal spray technologies such as plasma spray (APS) and High Velocity Oxy-Fuel Spray (HVOF)
  • APS plasma spray
  • HVOF High Velocity Oxy-Fuel Spray
  • molten or semi-molten particles with high kinetic energy are accelerated on a substrate where they impact, flattening and forming thin sheets which rapidly solidify.
  • the coating is formed by the overlapping of successive thin sheets forming an anisotropic lamellar structure. Said processes induce multiple imperfections of various types in the coating, where metastable phases of the original material can occur, in addition to inclusions of oxides, partially or totally non- melted particles, pores due to gases trapped or emitted by the substrate or fractures induced by the high cooling speed.
  • the dielectric strength of the alumina deposited by plasma spray (APS) takes on values in the order of 100-200 kv/cm, significantly lower than the 700kV/cm of the polycrystalline (ceramic) CX-Al 2 O 3 .
  • the presence of humidity absorbed in the thin sheets and pores and the gases included in the pores themselves contributes to said reduced dielectric strength of the insulating materials deposited by thermal spray. Consequently the discharge of the dielectric under voltage is controlled by a mechanism known as "corona effect" .
  • sealing agents have limited operating temperature ranges, as they are already unstable at temperatures below 400 0 C. Furthermore, no significant improvement of the dielectric characteristics has been achieved with said inorganic impregnating agents .
  • Our method sealing the open pores with a glass-based sealing agent, on alumina coatings deposited by APS, increases the discharge voltage by over 100%, in addition to ensuring absence of corrosion and oxidisation of the substrate up to 500 0 C and beyond, the upper limit of the operating temperature depending only on the type of glass used and any limits of the support.
  • the method consists in the following process phases: a) deposition on said coatings of a thin layer of a suspension of glass particles with appropriate granulometry, composition and coefficient of thermal expansion, by means of screen-printing, spraying, by immersion, by brush etc.; b) drying of the layer thus obtained; c) heating of the unit consisting of the base support, dielectric layer and glaze, to a temperature sufficient for melting the thin layer of glaze and penetration thereof into the -pores of the, dielectric material.
  • any further coating required can be performed by thermal spray.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Plasma & Fusion (AREA)
  • Physics & Mathematics (AREA)
  • Coating By Spraying Or Casting (AREA)
  • Paints Or Removers (AREA)
  • Glass Compositions (AREA)

Abstract

An innovative technique for improving the dielectric and anticorrosion characteristics of coatings obtained with thermal spray, APS, HVOF and analogous technologies, in particular insulating coats such as Al2O3. The deposits obtained with APS, HVOF and analogous technologies generally have a varying inherent porosity but is particularly significant for insulating coatings such as Al2O3, which suffer badly, in the breakdown tests, from the corona effect, a characteristic of non-compact materials. Said porosity furthermore permits the occurrence of phenomena of corrosion of the substrate due both to oxidisation and to interaction with corrosive gases and liquids penetrating through the open pores. The use of a sealing agent consisting of a suspension of glass particles with appropriate granulometry and coefficient of expansion in specific liquids, for example screen-printed and re-melted, seals the open pores of the coats obtained with APS, HVOF or similar, thus preventing all phenomena of corrosion and drastically reducing the corona effect.

Description

INNOVATIVE TECHNIQUE FOR IMPROVING THE DIELECTRIC AND ANTICORROSION CHARACTERISTICS OF COATINGS OBTAINED WITH THERMAL SPRAY, APS, HVOF AND ANALOGOUS TECHNOLOGIES, IN PARTICULAR INSULATING COATS SUCH AS AL2O3
STATE OF THE ART
In thermal spray technologies, such as plasma spray (APS) and High Velocity Oxy-Fuel Spray (HVOF) , molten or semi-molten particles with high kinetic energy are accelerated on a substrate where they impact, flattening and forming thin sheets which rapidly solidify. The coating is formed by the overlapping of successive thin sheets forming an anisotropic lamellar structure. Said processes induce multiple imperfections of various types in the coating, where metastable phases of the original material can occur, in addition to inclusions of oxides, partially or totally non- melted particles, pores due to gases trapped or emitted by the substrate or fractures induced by the high cooling speed. In the case of coatings consisting of dielectric materials, for example alumina, zirconium, alumina-titanium, these imperfections, and particularly the presence of porosity, reduce the resistance of the substrate to corrosion in addition to negatively affecting the dielectric properties of the coat itself. For example, the dielectric strength of the alumina deposited by plasma spray (APS) takes on values in the order of 100-200 kv/cm, significantly lower than the 700kV/cm of the polycrystalline (ceramic) CX-Al2O3. The presence of humidity absorbed in the thin sheets and pores and the gases included in the pores themselves contributes to said reduced dielectric strength of the insulating materials deposited by thermal spray. Consequently the discharge of the dielectric under voltage is controlled by a mechanism known as "corona effect" .
To mitigate these negative effects of the porosity, numerous treatments have been applied after the deposit including heating under a laser beam or electronic beam,, . Or under isostatic pressure, or impregnation by means :ofV; organic-.VOr. inorganic sealing agents. Compared to , other;-•.methpds,;f;tjie, use of sealing agents for impregnation is obviously; the, /simplest and cheapest method. The most commonly used sealing agents, based on epoxy, phenolic, siliconic etc. resins, are obviously not suitable for application of the coatings at high temperatures; for the latter type of application, inorganic sealing agents have been studied, based on aluminium phosphates, sodium silicates and similar. However, even the latter sealing agents have limited operating temperature ranges, as they are already unstable at temperatures below 4000C. Furthermore, no significant improvement of the dielectric characteristics has been achieved with said inorganic impregnating agents . Our method, sealing the open pores with a glass-based sealing agent, on alumina coatings deposited by APS, increases the discharge voltage by over 100%, in addition to ensuring absence of corrosion and oxidisation of the substrate up to 5000C and beyond, the upper limit of the operating temperature depending only on the type of glass used and any limits of the support.
OBJECT AND DESCRIPTION OF THE INVENTION
A significant reproducible improvement in the insulation and dielectric strength properties of coatings in alumina or equivalents, deposited by APS or HVOF, is obtained with a simple cost-effective method.
The method consists in the following process phases: a) deposition on said coatings of a thin layer of a suspension of glass particles with appropriate granulometry, composition and coefficient of thermal expansion, by means of screen-printing, spraying, by immersion, by brush etc.; b) drying of the layer thus obtained; c) heating of the unit consisting of the base support, dielectric layer and glaze, to a temperature sufficient for melting the thin layer of glaze and penetration thereof into the -pores of the, dielectric material.
Naturally the best results in terms of dielectric strength andcorrosion will be obtained by heating under a' vacuum. It is also obvious that the maximum dielectric strength, although still limited by a mitigated corona effect, can be obtained by using successive layers constituted as above.
Once the insulating and anticorrosion layer has been obtained, any further coating required can be performed by thermal spray.

Claims

CLAIMS .
1) An innovative technique for improvement- of. the dielectric characteristics of layers deposited by APS,- HVOF and similar, in particular insulating layers such as Al2O3 or equivalents, combined with improvement of resistance to corrosion of the relative substrates, characterised by a layer which seals the inherent porosity of said coatings obtained by APS, HVOF and similar, and which permits the use thereof at high temperatures, since the use of this new technology is limited only by the melting temperature of the glass used.
2) A technique as claimed in Claim 1, wherein the sealing layer consists of a suspension in a suitable liquid, e.g. alcohol or any bonding agents, of glass powder having granulometry and coefficient of thermal expansion compatible both with the layer, e.g. insulating, on which it will be deposited, and with the support on which said layer has been deposited.
3 ) A technique as claimed in Claim 1 and 2 , wherein the suspension of glass powder is transferred by means of screen- printing, spraying with an air gun or, better, a nitrogen gun, by brush, by immersion etc. on the layer deposited by APS, e.g. Al2O3 or similar.
4) A technique as claimed in Claim 1, 2 and 3, wherein said coat of glass powder is brought to a temperature sufficient for melting and penetration of the glass into the pores of the layer deposited by thermal spray, e.g. Al2O3 or similar.
5) A technique as claimed in Claim 1, 2, 3 and 4, wherein melting of the vitreous component of the sealing agent is performed preferably and if possible under a vacuum, thus obtaining the best performance in terms of resistance both to phenomena of corrosion of the support (oxidisation) and dόrrosion by external agents.
6) A technique . as claimed in the preceding Claims, wherein said porous layer hermetically sealed by the thin glaze, in itself sufficient in terms of resistance to phenomena of corrosion and improvement of the dielectric characteristics, can be further improved by successive layers as above or by coatings either applied in a subsequent phase or directly applied by APS, HVOF or similar, or chemically (e.g. Au or Ni electroless) followed by coatings applied by APS, HVOF, etc. for example by means of the processes claimed in the patent applications pending relative to the production of integrated and auto-regulated heating systems on pyroceram or glass cooker hobs and on metal plates .
PCT/IB2007/003028 2006-10-12 2007-10-11 Innovative technique for improving the dielectric and anticorrosion characteristics of coatings obtained with thermal spray, aps, hvof and analogous technologies, in particular insulating coats such as al2o3 WO2008044128A2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITMO2006A000322 2006-10-12
IT000322A ITMO20060322A1 (en) 2006-10-12 2006-10-12 INNOVATIVE TECHNIQUE FOR THE IMPROVEMENT OF THE DIELECTRIC AND ANTI-CORROSION CHARACTERISTICS OF FINISHES OBTAINED WITH THERMAL SPRAY, APS, HVOF AND ANALOGUE TECHNOLOGIES, IN PARTICULAR OF INSULATING REPORTS SUCH AS FOR ES. A1203.

Publications (2)

Publication Number Publication Date
WO2008044128A2 true WO2008044128A2 (en) 2008-04-17
WO2008044128A3 WO2008044128A3 (en) 2008-06-12

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PCT/IB2007/003028 WO2008044128A2 (en) 2006-10-12 2007-10-11 Innovative technique for improving the dielectric and anticorrosion characteristics of coatings obtained with thermal spray, aps, hvof and analogous technologies, in particular insulating coats such as al2o3

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2305672A (en) * 1995-09-29 1997-04-16 Aea Technology Plc An electrically isolating support for electronic components
US5714243A (en) * 1990-12-10 1998-02-03 Xerox Corporation Dielectric image receiving member
US5925228A (en) * 1997-01-09 1999-07-20 Sandia Corporation Electrophoretically active sol-gel processes to backfill, seal, and/or densify porous, flawed, and/or cracked coatings on electrically conductive material
EP1111089A1 (en) * 1999-12-13 2001-06-27 Sulzer Markets and Technology AG Method of sealing a porous layer onto the surface of an object, in particular for sealing a thermally sprayed layer
US20030170472A1 (en) * 2000-12-12 2003-09-11 Konica Corporation Layer forming method, product comprising the layer, optical film, dielectric-coated electrode and plasma discharge apparatus
US20030228416A1 (en) * 2002-06-11 2003-12-11 Shunichi Iwamaru Dielectric-coated electrode, plasma discharge treatment apparatus and method for forming thin film
WO2007140494A1 (en) * 2006-06-07 2007-12-13 Ab Mikroelektronik Gesellschaft Mit Beschränkter Haftung Circuit carrier

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5714243A (en) * 1990-12-10 1998-02-03 Xerox Corporation Dielectric image receiving member
GB2305672A (en) * 1995-09-29 1997-04-16 Aea Technology Plc An electrically isolating support for electronic components
US5925228A (en) * 1997-01-09 1999-07-20 Sandia Corporation Electrophoretically active sol-gel processes to backfill, seal, and/or densify porous, flawed, and/or cracked coatings on electrically conductive material
EP1111089A1 (en) * 1999-12-13 2001-06-27 Sulzer Markets and Technology AG Method of sealing a porous layer onto the surface of an object, in particular for sealing a thermally sprayed layer
US20030170472A1 (en) * 2000-12-12 2003-09-11 Konica Corporation Layer forming method, product comprising the layer, optical film, dielectric-coated electrode and plasma discharge apparatus
US20030228416A1 (en) * 2002-06-11 2003-12-11 Shunichi Iwamaru Dielectric-coated electrode, plasma discharge treatment apparatus and method for forming thin film
WO2007140494A1 (en) * 2006-06-07 2007-12-13 Ab Mikroelektronik Gesellschaft Mit Beschränkter Haftung Circuit carrier

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Publication number Publication date
WO2008044128A3 (en) 2008-06-12
ITMO20060322A1 (en) 2008-04-13

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