CA2006992A1 - Powder of plastic and treated mineral - Google Patents
Powder of plastic and treated mineralInfo
- Publication number
- CA2006992A1 CA2006992A1 CA002006992A CA2006992A CA2006992A1 CA 2006992 A1 CA2006992 A1 CA 2006992A1 CA 002006992 A CA002006992 A CA 002006992A CA 2006992 A CA2006992 A CA 2006992A CA 2006992 A1 CA2006992 A1 CA 2006992A1
- Authority
- CA
- Canada
- Prior art keywords
- thermal spray
- powder
- spray powder
- silane
- mineral
- Prior art date
- Legal status (The legal status 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 status listed.)
- Abandoned
Links
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
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
- B22F1/102—Metallic powder coated with organic material
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Plasma & Fusion (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Coating By Spraying Or Casting (AREA)
- Paints Or Removers (AREA)
- Application Of Or Painting With Fluid Materials (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A thermal spray powder is formed of a blend of particles of a polymeric powder and a mineral wherein the mineral particles, and preferably also the polymeric particles, each have a coating layer thereon approximately one monolayer thick. The layer is an organofunctional silane which includes an organofunctional group such as an amino propyltriethoxy. The silane is formed from a precursor silane having a hydrolyzable group bondable to the mineral constituent upon hydrolyzing of the hydrolyzable group.
Desirably the mineral is silicon aluminum alloy and the polymeric powder is a poly(para-oxybenzoyl)ester.
A thermal spray powder is formed of a blend of particles of a polymeric powder and a mineral wherein the mineral particles, and preferably also the polymeric particles, each have a coating layer thereon approximately one monolayer thick. The layer is an organofunctional silane which includes an organofunctional group such as an amino propyltriethoxy. The silane is formed from a precursor silane having a hydrolyzable group bondable to the mineral constituent upon hydrolyzing of the hydrolyzable group.
Desirably the mineral is silicon aluminum alloy and the polymeric powder is a poly(para-oxybenzoyl)ester.
Description
~oo~99~
Patent POWDER OF PLASTIC AND TREATED MINERAL
The present invention relates to a thermal spray powder formed of a plastic and a mineral, and particularly to such a powder characterized by improved cohesive strength and bonding when thermal sprayed onto plastic substrates.
BACKGROUND OF THE INVENTION
Many mechanical parts in automobiles and airplanes have special mineral coatings such as metal or ceramic for special properties such as hardness, wear resistance, etc. Such coatings are provided on parts ~uch as gears, pulleys, shafts, and the like, made of metal. However, the metal part itself is often just a carrier for the coating and could be replaced by lighter weight, often easier to fabricate, plastic if it were possible suitably to coat the plastic.
;
A simple technique for coating surfaces with metal or ceramic is by thermal (flame) spraying, employing either powder or wire.
When attempting to thermal spray onto plastic, however, special problems are encountered. Upon coolinq, the sprayed metal contracts and may warp or distort the plastic. The coating sometimes fails to adhere uniformly. The plastic substrate may melt from the material beinq sprayed and lose its shape, or the plastic surface may burn or decompose.
As disclosed in U.S. Patent No. 4,388,373 (Longo et al) it has been found that plastic substrates can be flame sprayed with a mineral powder which has been admixed with small amounts of nylon and epoxy polymers in powder form. The powder particles in `' Y
:
finely sub-divided form may be agglomerated with a binder or ; adhesive, mixed and dried, the agglomerates being composed of sub-articles of the individual components and being screened to recover particles of a particular size. The resulting agglomerates, or a simple powder mixture itself, can be flame sprayed in conventional manner onto the substrate. The coating can range in thickness from about 25 um to 5 mm or greater.
A composite powder of austenitic stainless steel, epoxy and nylon according to the above-described patent (assigned to a predecessor of the present assignee) has been quite successful for producing a thermal spray coating on plastic substrates, either for bonding another thermal spray coating or for use as is. However, spray technique is so~ewhat critical causing lS variation in results, and further improvement in bonding and cohesive strengths has been in demand. Also, for certain applications a different plastic constituent for the coating material is necessary or desired, for example a high temperature plastic.
U.S. Patent No. 3,723,165 ~Longo and Durmann) discloses thermal spray coating material~ comprising a high temperature plastic and a metal. Tn particular a silicon aluminum powder blended with poly~para-oxybenzoyl)ester in accordance with Example 1 of the patent has been highly 6uccessful commercially as an abradable coating for turbine blade seals and the like in gas turbine engines. Again, however, the spraying is technique dependent and improved bonding and cohesiveness are desired.
Various binders have been used or suggested for forming composite thermal spray powders. For example, U.S. Patent No. 3t617r358 (Dittrich) discloses spray drying to produce thermal spray ;~ 0699Z
powders of fine particles agglomerated with any of a variety of binders. Usually the binder is burned off, but may not be in certain cases. For example, U.S. Patent No. 4,593,007 (Novinski) teaches silicon dioxide derived from ethyl silicate in the binder for producing an abradable and erosion resistant coating of an oxide and aluminum.
Silane coupling agent~, such as described in a text book ~Silane Coupling Agents~ by E.P. Plueddemann (1982 Plenum Press, New York NY), for example Chapter l(pp. 1-28) have been used traditionally in the fiber glass industry to improve the integrity and moisture resistance of composites reinforced with glass fibers.
Organofunctional silanes are hybrid organic-inorganic compounds that are used as coupling agents. There exists more than one theory as to how silanes couple polymers and minerals, one of which is the formation of covalent bonds. The covalent bonds are formed during the curing cycle of the resin during the manufacture of the composite.
.
Objects of the present invention are to provide an improved plastic-containing thermal spray powder, to provide such a powder having improved bonding and cohesive strengths, to produce plastic-containing thermal spray coatings with reduced technique dependence, to provide a novel thermal spray material for bonding to plastic substrates, to provide a relatively high temperature plafitic bonding powder, and to produce an improved abradable coating.
SUMMARY OF THE INVENTION
The foregoing and other objects are achieved by a thermal spray powder formed of a polymeric constituent and a mineral .
.
. ~)06992 constituent, wherein at least the mineral constituent has a coating layer thereon comprising an organofunctional silane. The coating layer should be approximately one monolayer thick.
Preferably the mineral constituent contains silicon and is, for example, a silicon aluminum alloy.
The silane preferably includes an organofunctional group of the amino or vinyl type. The silane should be ~ormed from a precursor silane having a hydrolyzable group bondable to the mineral constituent upon hydrolyzing of the hydrolyzable group.
Desirably the polymeric constituent also has a silane layer thereon and may comprise, for example, a poly(para-oxybenzoyl)ester or an epoxy.
The foregoing and other objects are further achieved by a process for manufacturing a thermal spray powder, comprising forming a slurry of a mineral powder with an aqueous solution of an organofunctional silane having a hydrolyzable group, drying the slurry to form silane coated powder particles, and blending the coated powder with a polymeric powder. Preferably and conveniently the polymeric powder is blended in the slurry such that the thermal spray powder also includes silane coated polymer powder particles. The objects are further achieved with a thermal spray powder formed by this manufacturinq process, and by thermal spraying the powder formed thereby.
DETAILED DESCRIPTION OF THE INVENTION
Broadly a thermal spray powder of the present invention is formed of a mineral constituent and a polymeric constituent. The mineral constituent may be any conventional or desired inorganic 00~95`;~
material utilized for thermal spraying. Examples are listed extensively in the aforementioned U.S. Patent No. 4,388,373 and U.S. Patent No. 3,617,358, both of which are incorporated herein by reference. Preferably, for reasons presented below, the mineral contains~silicon. Thus the mineral may be silicon itself; one or more silicides of titanium, zirconium, hafnium, vanadium, niobium, tantalum, molybdenum, tungsten, chromium, or boron; a silicate or glas~ such as 3A12032SiO2 (mullite), BaO2SiO2, BaOA1203SiO2, BaOTiO2SiO2, 2~aosio2, Cr23si2~
Er2O3SiO2, ZrO2SiO2 (zircon), 2MgOSiO~, ZrOZrO2SiO2; or a silicon alloy of aluminum, bronze, nickel, cobalt or iron.
The polymeric constituent may be any conventional or desired thermal sprayable plastic such as polyester, epoxy, nylon, polyimide, polyether-ether-ketone or combinations thereof; or a high temperature plastic such as disclosed in aforementioned U.S.
Patent No. 3,723,165. Examples of these high temperature plastics include the well-known polyimide plastics, polyamide-imide plastics, the polyester-imide plastics and the aromatic polyester plastics. Particularly suitable are high temperature aromatic polyester plastics of the type formed from phenyl acetate, as for example the poly(para-oxybenzoly)ester or poly(para-oxybenzoylmethyl)ester, or a co-polyester of the type disclosed in U.S. Patent No. 3,784,405 (Economy et al).
Generally the powder is in the conventional size range, vis.
-147 ~5 microns, preferably -88 +44 microns or alternatively -44 ~5 microns. Also, in a preferred embodiment the powder is a simple blend of a mineral powder and a polymeric powder, as distinguished from a composite powder. However, a composite powder wherein a fine powder of one constituent is clad onto core particles of the other constituent is an alternative. Yet .
another alternative is a composite powder formed of fine powder constituents with a binder and produced by spray drying as taught ; in aforementioned U.S. Patent No. 3,617,358 or by mixing and stirring as taught in aforementioned U.S. Patent No. 4,388,373.
` 5 The proportion of plastic to mineral should generally be in the range of 5~ to 95% by volume, and preferably 5% to 25~.
;:
According to the present invention at least the mineral constituent is treated such that each powder particle has a coating layer thereon comprising an organofunctional silane.
: Preferably the polymeric constituent is also so treated. The coating layer should have a thickness between about one half and two monolayers of silane, i.e. approximately one monolayer.
Organofunctional silanes are composed of two functional groups attached to a silicon ~Si) atom. The general formula is X3SiRY.
The (Y) is an organofunctional group which is chosen for reactivity or compatibility with a polymer, while the (X) is a hydrolyzable group which merely acts as an intermediate in the formation of silanol groups for bonding to mineral surfaces. In the presence of water, the (X) group hydrolyzes to form a radical OH- group which then bonds to the electrophilic mineral (M+~.
The ~R) is a conventional silane radial.
The cilane will yield optimum coupling if it has a monolayer couerage of the surface. The surface area of the powder needs to be determined to estimate the required concentration of the silane treatment. Surface area may be measured by the conventional B.E.T. analysis method.
Z~06992 Preferably the silane includes an organofunctional group of the amino type or the vinyl type. More specifically the organofunctional group should be an aminopropyltriethoxy or glycidoxypropyltrimethoxy.
:: S
The inorganic functional groups of the silane are believed to bond best to silica. Therefore it is quite desirable that the mineral powder contain silicon as described above. The requirement is fulfilled directly if the mineral contains silica for example as glass. However, silicon per se or as a silicide or in alloy form is suitable, becau~e there is some normal oxidation of the silicon during the thermal spraying process. A
particularly preferable mineral is based on aluminum metal which has a coefficient of thermal expansion similar to that of most plastics. Thus silicon aluminum alloy, for example containing about 12% silicon, balance aluminum, is most preferable.
A suitable method to manufacture a powder according to the present invention, the plastic and metallic constituents are blended in a steam heated pot. A silane solution diluted with 95~ to 99% water is added to get the mixture to a homogeneous ~lurry. The steam is turned on to drive off the water. ~nce the powder is dry and free flowing it is removed and screened.
Alternatively, only the mineral powder i6 SO treated, and the 25 pla8tic powder i8 blended in afterward.
The steam pot drying of the powder is at sufficiently loY
temperature so as not to cure the plastic constituent or the silane with respect to it. Thus it has been discovered that the thermal spraying step which melts Ol at least surface heat softens the powder constituents effects the appropriate heat treatment to achieve excellent bonding and coating cohesion, ~)0699Z
without a high degree of spray technique dependence. It is not yet understood how this occurs, e.g. whether the (X) group hydrolizes and reacts with the mineral powder during the ; manufacturing process while the (Y) remains unreacted until the thermal spraying~process.
Coatings from about 25 microns to several millimeters in thickness may be produced by any of the powder thermal spray processes such as with a combustion spray gun of the type described in ~.S. Patent No. 3,455,510 (Rotolico) or a plasma spray gun of the type described in U.S. Patent No. 3,145,287 (Seibein et al) or a high velocity oxygen-fuel gun such as described in U.S. Patent NoO 4,416,421 (Browning).
ExamPle 1 A blend of 40% by weight (56~ by volume) of a high temperature aromatic polyester plastic, poly(para-oxybenzoyl)ester, sold under the trade name of ERONOL by the Carborundum Company, Sanford, N.Y., having a size of -88 +44, microns is blended with 60% by weight (44~ by volume) of a ~ilicon-aluminum alloy containing 12 weight percent silicon and a size of -325 ~10 microns. These plastic and metallic constituents were blended in a steam heated pot. A triaminopropyltriethoxysilane solution diluted with 99% water is added to form a homogeneous lurry.
The steam is turned on to drive off the water and dry the powder.
Once the powder is free flowing it is removed and screened to -88 +44 microns.
The blend is sprayed with a high velocity oxygen-fuel spray gun specifically a Metco Type DJ(TM) gun sold by The Perkin-Elmer Corporation, Westbury, New York, using a ~3 insert, ~3 injector, .'' ' '. '` ~
:
~A" shell, t2 siphon plug and ~2 air cap. Oxygen was 10.5 kg/cm2 ! (150 psig) and 212 l/min (450 scfh), propylene gas at 7.0 kg/cm2 (100 psig) and 47 l/min (100 scfh), and air at 5.3 kg/cm2 (75 psig) and 290 l/min (615 scfh). A high pressure powder feeder sold as a Metco ~ype DJP powder feeder by Perkin-Elmer is used to feed the powder blend at 1.6 kg/hr in a nitrogen carrier at 8.8 kg/cm2 (125 psig) and 7 l/min (15 scfh). Spray distance is 20 cm.
Coatings 2.54 mm thickness were produced on a polyimide PMR-15/carbon fiber composite sold by ~ysol Composites, Cleveland Ohio and prepared by light grit blasting. The coatings had a bond strength of 1.28 kg/cm2 (900 psi), compared with 0.28 kg/cm2 (200 psi) for a coating of Example 1 of the aforementioned U.S.
Patent No. 4,388,373 (Metco 625 powder) on a similar substrate.
A 100 micron thick coating of the present example had a surface roughness of at least 12 microns (500 microinches) aa, so as to be ideal for subsequent application of a mineral overcoat. After deposition of the overcoat, the bond to the plastic substrate was so tenacious that in test fractures metal particles adhered to the plastic substrate, pointing up the strong adhesion of the undercoat-overcoat combination to the plastic. Overcoating with thermal sprayed coatings of aluminum-bronze, nickel chromium and austenitic stainless steel give 6trongly adherent overcoat~.
Photomicrographs clearly show the reason for the difference in the bond strengths. Cross sections at a magnification of 500X of coatings on a laminate using untreated powder in the blend reveal extensive microcracking between the coating and the substrate.
Coatings produced with powder treated according the present example show no such cracking.
~(~06992 Ex~mEl_~
Example 1 is repeated with a Metco Type 9MB plasma spray gun using a Metco Type 4MP powder feeder, using the following parameters: 733 nozzle, No. 2 feed port, argon plasma gas at 100 psi and 100 l/min (212 scfh) flow, hydrogen secondary gas at 3.5 kg/cm2 (50 psi) and 9 l/min ~19 scfh) flow, 500 amperes and 70 volts, cooling air jets at 5.25 kg/cm2 (75 psi), 1.5 kg/hr powder feed rate in argon carrier gas, and 9 cm spray distance. Bond strength is again very good.
Exam~le 3 Example 1 is repeated with a different polymer powder, namely a bisphenol a epoxy. The epoxy powder is about 8~ by weight (15 by volume). Similar sesults are effected.
ExamPle 4 Example 1 is repeated using a different silane, namely glycidoxypropyltrimethoxysilane, in 99~ by weight (99% by volume) water. Similar results are effected.
ExamDle 5 Example 1 is repeated except a coating 3.2 mm thick is produced on a turbine shroud of nickel alloy for the compressor section of a gas turbine engine. For this purpose of coating onto a metal surface, a bond coat of nickel aluminide is used. An excellent, abradable, cohesive coating results.
~(~;992 ExamPle 6 Example 1 i8 repeated except that the polyester is replaced with a copolyester of recurring units of Formula I, III, and IV as disclosed in the aforementioned U.S. Patent No. 3,784,405 (incorporated herein by reference) and sold as Xydar~TM) by Dartco Manufacturing Inc., Augusta, Georgia. The blend contains about 25% by weight (61% by volume) of the polymer. Similar results are effected.
While the invention has been described above in detail with reference to specific embodiments, variouE changes and modifications which fall within the spirit of the invention and scope of the appended claims will become apparent to those lS skilled in this art. The invention is therefore only intended to ; be limited by the appended claims or their equivalents.
Patent POWDER OF PLASTIC AND TREATED MINERAL
The present invention relates to a thermal spray powder formed of a plastic and a mineral, and particularly to such a powder characterized by improved cohesive strength and bonding when thermal sprayed onto plastic substrates.
BACKGROUND OF THE INVENTION
Many mechanical parts in automobiles and airplanes have special mineral coatings such as metal or ceramic for special properties such as hardness, wear resistance, etc. Such coatings are provided on parts ~uch as gears, pulleys, shafts, and the like, made of metal. However, the metal part itself is often just a carrier for the coating and could be replaced by lighter weight, often easier to fabricate, plastic if it were possible suitably to coat the plastic.
;
A simple technique for coating surfaces with metal or ceramic is by thermal (flame) spraying, employing either powder or wire.
When attempting to thermal spray onto plastic, however, special problems are encountered. Upon coolinq, the sprayed metal contracts and may warp or distort the plastic. The coating sometimes fails to adhere uniformly. The plastic substrate may melt from the material beinq sprayed and lose its shape, or the plastic surface may burn or decompose.
As disclosed in U.S. Patent No. 4,388,373 (Longo et al) it has been found that plastic substrates can be flame sprayed with a mineral powder which has been admixed with small amounts of nylon and epoxy polymers in powder form. The powder particles in `' Y
:
finely sub-divided form may be agglomerated with a binder or ; adhesive, mixed and dried, the agglomerates being composed of sub-articles of the individual components and being screened to recover particles of a particular size. The resulting agglomerates, or a simple powder mixture itself, can be flame sprayed in conventional manner onto the substrate. The coating can range in thickness from about 25 um to 5 mm or greater.
A composite powder of austenitic stainless steel, epoxy and nylon according to the above-described patent (assigned to a predecessor of the present assignee) has been quite successful for producing a thermal spray coating on plastic substrates, either for bonding another thermal spray coating or for use as is. However, spray technique is so~ewhat critical causing lS variation in results, and further improvement in bonding and cohesive strengths has been in demand. Also, for certain applications a different plastic constituent for the coating material is necessary or desired, for example a high temperature plastic.
U.S. Patent No. 3,723,165 ~Longo and Durmann) discloses thermal spray coating material~ comprising a high temperature plastic and a metal. Tn particular a silicon aluminum powder blended with poly~para-oxybenzoyl)ester in accordance with Example 1 of the patent has been highly 6uccessful commercially as an abradable coating for turbine blade seals and the like in gas turbine engines. Again, however, the spraying is technique dependent and improved bonding and cohesiveness are desired.
Various binders have been used or suggested for forming composite thermal spray powders. For example, U.S. Patent No. 3t617r358 (Dittrich) discloses spray drying to produce thermal spray ;~ 0699Z
powders of fine particles agglomerated with any of a variety of binders. Usually the binder is burned off, but may not be in certain cases. For example, U.S. Patent No. 4,593,007 (Novinski) teaches silicon dioxide derived from ethyl silicate in the binder for producing an abradable and erosion resistant coating of an oxide and aluminum.
Silane coupling agent~, such as described in a text book ~Silane Coupling Agents~ by E.P. Plueddemann (1982 Plenum Press, New York NY), for example Chapter l(pp. 1-28) have been used traditionally in the fiber glass industry to improve the integrity and moisture resistance of composites reinforced with glass fibers.
Organofunctional silanes are hybrid organic-inorganic compounds that are used as coupling agents. There exists more than one theory as to how silanes couple polymers and minerals, one of which is the formation of covalent bonds. The covalent bonds are formed during the curing cycle of the resin during the manufacture of the composite.
.
Objects of the present invention are to provide an improved plastic-containing thermal spray powder, to provide such a powder having improved bonding and cohesive strengths, to produce plastic-containing thermal spray coatings with reduced technique dependence, to provide a novel thermal spray material for bonding to plastic substrates, to provide a relatively high temperature plafitic bonding powder, and to produce an improved abradable coating.
SUMMARY OF THE INVENTION
The foregoing and other objects are achieved by a thermal spray powder formed of a polymeric constituent and a mineral .
.
. ~)06992 constituent, wherein at least the mineral constituent has a coating layer thereon comprising an organofunctional silane. The coating layer should be approximately one monolayer thick.
Preferably the mineral constituent contains silicon and is, for example, a silicon aluminum alloy.
The silane preferably includes an organofunctional group of the amino or vinyl type. The silane should be ~ormed from a precursor silane having a hydrolyzable group bondable to the mineral constituent upon hydrolyzing of the hydrolyzable group.
Desirably the polymeric constituent also has a silane layer thereon and may comprise, for example, a poly(para-oxybenzoyl)ester or an epoxy.
The foregoing and other objects are further achieved by a process for manufacturing a thermal spray powder, comprising forming a slurry of a mineral powder with an aqueous solution of an organofunctional silane having a hydrolyzable group, drying the slurry to form silane coated powder particles, and blending the coated powder with a polymeric powder. Preferably and conveniently the polymeric powder is blended in the slurry such that the thermal spray powder also includes silane coated polymer powder particles. The objects are further achieved with a thermal spray powder formed by this manufacturinq process, and by thermal spraying the powder formed thereby.
DETAILED DESCRIPTION OF THE INVENTION
Broadly a thermal spray powder of the present invention is formed of a mineral constituent and a polymeric constituent. The mineral constituent may be any conventional or desired inorganic 00~95`;~
material utilized for thermal spraying. Examples are listed extensively in the aforementioned U.S. Patent No. 4,388,373 and U.S. Patent No. 3,617,358, both of which are incorporated herein by reference. Preferably, for reasons presented below, the mineral contains~silicon. Thus the mineral may be silicon itself; one or more silicides of titanium, zirconium, hafnium, vanadium, niobium, tantalum, molybdenum, tungsten, chromium, or boron; a silicate or glas~ such as 3A12032SiO2 (mullite), BaO2SiO2, BaOA1203SiO2, BaOTiO2SiO2, 2~aosio2, Cr23si2~
Er2O3SiO2, ZrO2SiO2 (zircon), 2MgOSiO~, ZrOZrO2SiO2; or a silicon alloy of aluminum, bronze, nickel, cobalt or iron.
The polymeric constituent may be any conventional or desired thermal sprayable plastic such as polyester, epoxy, nylon, polyimide, polyether-ether-ketone or combinations thereof; or a high temperature plastic such as disclosed in aforementioned U.S.
Patent No. 3,723,165. Examples of these high temperature plastics include the well-known polyimide plastics, polyamide-imide plastics, the polyester-imide plastics and the aromatic polyester plastics. Particularly suitable are high temperature aromatic polyester plastics of the type formed from phenyl acetate, as for example the poly(para-oxybenzoly)ester or poly(para-oxybenzoylmethyl)ester, or a co-polyester of the type disclosed in U.S. Patent No. 3,784,405 (Economy et al).
Generally the powder is in the conventional size range, vis.
-147 ~5 microns, preferably -88 +44 microns or alternatively -44 ~5 microns. Also, in a preferred embodiment the powder is a simple blend of a mineral powder and a polymeric powder, as distinguished from a composite powder. However, a composite powder wherein a fine powder of one constituent is clad onto core particles of the other constituent is an alternative. Yet .
another alternative is a composite powder formed of fine powder constituents with a binder and produced by spray drying as taught ; in aforementioned U.S. Patent No. 3,617,358 or by mixing and stirring as taught in aforementioned U.S. Patent No. 4,388,373.
` 5 The proportion of plastic to mineral should generally be in the range of 5~ to 95% by volume, and preferably 5% to 25~.
;:
According to the present invention at least the mineral constituent is treated such that each powder particle has a coating layer thereon comprising an organofunctional silane.
: Preferably the polymeric constituent is also so treated. The coating layer should have a thickness between about one half and two monolayers of silane, i.e. approximately one monolayer.
Organofunctional silanes are composed of two functional groups attached to a silicon ~Si) atom. The general formula is X3SiRY.
The (Y) is an organofunctional group which is chosen for reactivity or compatibility with a polymer, while the (X) is a hydrolyzable group which merely acts as an intermediate in the formation of silanol groups for bonding to mineral surfaces. In the presence of water, the (X) group hydrolyzes to form a radical OH- group which then bonds to the electrophilic mineral (M+~.
The ~R) is a conventional silane radial.
The cilane will yield optimum coupling if it has a monolayer couerage of the surface. The surface area of the powder needs to be determined to estimate the required concentration of the silane treatment. Surface area may be measured by the conventional B.E.T. analysis method.
Z~06992 Preferably the silane includes an organofunctional group of the amino type or the vinyl type. More specifically the organofunctional group should be an aminopropyltriethoxy or glycidoxypropyltrimethoxy.
:: S
The inorganic functional groups of the silane are believed to bond best to silica. Therefore it is quite desirable that the mineral powder contain silicon as described above. The requirement is fulfilled directly if the mineral contains silica for example as glass. However, silicon per se or as a silicide or in alloy form is suitable, becau~e there is some normal oxidation of the silicon during the thermal spraying process. A
particularly preferable mineral is based on aluminum metal which has a coefficient of thermal expansion similar to that of most plastics. Thus silicon aluminum alloy, for example containing about 12% silicon, balance aluminum, is most preferable.
A suitable method to manufacture a powder according to the present invention, the plastic and metallic constituents are blended in a steam heated pot. A silane solution diluted with 95~ to 99% water is added to get the mixture to a homogeneous ~lurry. The steam is turned on to drive off the water. ~nce the powder is dry and free flowing it is removed and screened.
Alternatively, only the mineral powder i6 SO treated, and the 25 pla8tic powder i8 blended in afterward.
The steam pot drying of the powder is at sufficiently loY
temperature so as not to cure the plastic constituent or the silane with respect to it. Thus it has been discovered that the thermal spraying step which melts Ol at least surface heat softens the powder constituents effects the appropriate heat treatment to achieve excellent bonding and coating cohesion, ~)0699Z
without a high degree of spray technique dependence. It is not yet understood how this occurs, e.g. whether the (X) group hydrolizes and reacts with the mineral powder during the ; manufacturing process while the (Y) remains unreacted until the thermal spraying~process.
Coatings from about 25 microns to several millimeters in thickness may be produced by any of the powder thermal spray processes such as with a combustion spray gun of the type described in ~.S. Patent No. 3,455,510 (Rotolico) or a plasma spray gun of the type described in U.S. Patent No. 3,145,287 (Seibein et al) or a high velocity oxygen-fuel gun such as described in U.S. Patent NoO 4,416,421 (Browning).
ExamPle 1 A blend of 40% by weight (56~ by volume) of a high temperature aromatic polyester plastic, poly(para-oxybenzoyl)ester, sold under the trade name of ERONOL by the Carborundum Company, Sanford, N.Y., having a size of -88 +44, microns is blended with 60% by weight (44~ by volume) of a ~ilicon-aluminum alloy containing 12 weight percent silicon and a size of -325 ~10 microns. These plastic and metallic constituents were blended in a steam heated pot. A triaminopropyltriethoxysilane solution diluted with 99% water is added to form a homogeneous lurry.
The steam is turned on to drive off the water and dry the powder.
Once the powder is free flowing it is removed and screened to -88 +44 microns.
The blend is sprayed with a high velocity oxygen-fuel spray gun specifically a Metco Type DJ(TM) gun sold by The Perkin-Elmer Corporation, Westbury, New York, using a ~3 insert, ~3 injector, .'' ' '. '` ~
:
~A" shell, t2 siphon plug and ~2 air cap. Oxygen was 10.5 kg/cm2 ! (150 psig) and 212 l/min (450 scfh), propylene gas at 7.0 kg/cm2 (100 psig) and 47 l/min (100 scfh), and air at 5.3 kg/cm2 (75 psig) and 290 l/min (615 scfh). A high pressure powder feeder sold as a Metco ~ype DJP powder feeder by Perkin-Elmer is used to feed the powder blend at 1.6 kg/hr in a nitrogen carrier at 8.8 kg/cm2 (125 psig) and 7 l/min (15 scfh). Spray distance is 20 cm.
Coatings 2.54 mm thickness were produced on a polyimide PMR-15/carbon fiber composite sold by ~ysol Composites, Cleveland Ohio and prepared by light grit blasting. The coatings had a bond strength of 1.28 kg/cm2 (900 psi), compared with 0.28 kg/cm2 (200 psi) for a coating of Example 1 of the aforementioned U.S.
Patent No. 4,388,373 (Metco 625 powder) on a similar substrate.
A 100 micron thick coating of the present example had a surface roughness of at least 12 microns (500 microinches) aa, so as to be ideal for subsequent application of a mineral overcoat. After deposition of the overcoat, the bond to the plastic substrate was so tenacious that in test fractures metal particles adhered to the plastic substrate, pointing up the strong adhesion of the undercoat-overcoat combination to the plastic. Overcoating with thermal sprayed coatings of aluminum-bronze, nickel chromium and austenitic stainless steel give 6trongly adherent overcoat~.
Photomicrographs clearly show the reason for the difference in the bond strengths. Cross sections at a magnification of 500X of coatings on a laminate using untreated powder in the blend reveal extensive microcracking between the coating and the substrate.
Coatings produced with powder treated according the present example show no such cracking.
~(~06992 Ex~mEl_~
Example 1 is repeated with a Metco Type 9MB plasma spray gun using a Metco Type 4MP powder feeder, using the following parameters: 733 nozzle, No. 2 feed port, argon plasma gas at 100 psi and 100 l/min (212 scfh) flow, hydrogen secondary gas at 3.5 kg/cm2 (50 psi) and 9 l/min ~19 scfh) flow, 500 amperes and 70 volts, cooling air jets at 5.25 kg/cm2 (75 psi), 1.5 kg/hr powder feed rate in argon carrier gas, and 9 cm spray distance. Bond strength is again very good.
Exam~le 3 Example 1 is repeated with a different polymer powder, namely a bisphenol a epoxy. The epoxy powder is about 8~ by weight (15 by volume). Similar sesults are effected.
ExamPle 4 Example 1 is repeated using a different silane, namely glycidoxypropyltrimethoxysilane, in 99~ by weight (99% by volume) water. Similar results are effected.
ExamDle 5 Example 1 is repeated except a coating 3.2 mm thick is produced on a turbine shroud of nickel alloy for the compressor section of a gas turbine engine. For this purpose of coating onto a metal surface, a bond coat of nickel aluminide is used. An excellent, abradable, cohesive coating results.
~(~;992 ExamPle 6 Example 1 i8 repeated except that the polyester is replaced with a copolyester of recurring units of Formula I, III, and IV as disclosed in the aforementioned U.S. Patent No. 3,784,405 (incorporated herein by reference) and sold as Xydar~TM) by Dartco Manufacturing Inc., Augusta, Georgia. The blend contains about 25% by weight (61% by volume) of the polymer. Similar results are effected.
While the invention has been described above in detail with reference to specific embodiments, variouE changes and modifications which fall within the spirit of the invention and scope of the appended claims will become apparent to those lS skilled in this art. The invention is therefore only intended to ; be limited by the appended claims or their equivalents.
Claims (21)
1. A thermal spray powder formed of a polymeric constituent and a mineral constituent, wherein the mineral constituent has a coating layer thereon comprising an organofunctional silane.
2. A thermal spray powder according to Claim 1, wherein the mineral constituent is selected from the group consisting of metals, silicon and alloys thereof.
3. A thermal spray powder according to Claim 2, wherein the mineral constituent is a metallic alloy containing silicon.
4. A thermal spray powder according to Claim 3, wherein the metallic alloy is silicon aluminum.
5. A thermal spray powder according to Claim 2, wherein the mineral constituent comprises aluminum.
6. A thermal spray powder according to Claim 1, wherein the coating layer is approximately one monolayer thick.
7. A thermal spray powder according to Claim 1, wherein the silane includes an organofunctional group of the amino type or the vinyl type.
8. A thermal spray powder according to Claim 7, wherein the organofunctional group is amino propyltriethoxy or glyidoxypropyltrimethoxy.
9. A thermal spray powder according to Claim 1, wherein the silane is formed from a hydrolyzable silane group bondable to the mineral constituent upon hydrolyzing of the hydrolyzable group.
10. A thermal spray powder according to Claim 1, wherein the powder is formed as a simple blend of a first powder consisting essentially of the polymeric constituent and a second powder consisting essentially of the silane coated mineral constituent.
11. A thermal spray powder according to Claim 1, wherein the polymeric constituent is a modified polyester.
12. A thermal spray powder according to Claim 1, wherein the polymeric constituent is a poly(para-oxybenzoyl)ester.
13. A thermal spray powder according to Claim 1, wherein the polymeric constituent has a coating layer thereon comprising the organofunctional silane.
14. A thermal spray powder formed of a blend of particles of a polymeric powder and a silicon aluminum alloy, wherein the polymeric particles and the alloy particles each have a coating layer thereon approximately one monolayer thick comprising an organofunctional silane, the silane including a amino propyl triethoxy organofunctional group and being formed from a precursor silane having a hydrolyzable group bondable to the mineral constituent upon hydrolyzing of the hydrolyzable group.
15. A thermal spray powder according to Claim 15, wherein the polymeric powder is a poly(para-oxybenzoyl) ester.
16. A process of manufacturing a thermal spray powder, comprising forming a slurry of a mineral powder with an aqueous solution of hydrolyzable organofunctional silane, drying the slurry to form a silane coated powder, and blending the coated powder with a polymeric powder.
17. A process according to Claim 17, wherein the polymeric powder is blended with the mineral powder in the slurry prior to drying.
18. A thermal spray powder formed by the process of Claim 17.
19. A thermal spray powder formed by the process of Claim 18.
20. A process for producing a well bonded and coherent polymer-containing coating comprising thermal spraying the thermal spray powder of Claim 19.
21. A process for producing a well bonded and coherent polymer-containing coating comprising thermal spraying the thermal spray powder of Claim 20.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US30264489A | 1989-01-26 | 1989-01-26 | |
| US302,644 | 1989-01-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2006992A1 true CA2006992A1 (en) | 1990-07-26 |
Family
ID=23168629
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002006992A Abandoned CA2006992A1 (en) | 1989-01-26 | 1990-01-02 | Powder of plastic and treated mineral |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0379995A1 (en) |
| JP (1) | JPH02232351A (en) |
| CN (1) | CN1044484A (en) |
| BR (1) | BR9000315A (en) |
| CA (1) | CA2006992A1 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5455080A (en) * | 1992-08-26 | 1995-10-03 | Armco Inc. | Metal substrate with enhanced corrosion resistance and improved paint adhesion |
| US5660934A (en) * | 1994-12-29 | 1997-08-26 | Spray-Tech, Inc. | Clad plastic particles suitable for thermal spraying |
| ES2220228B1 (en) * | 2003-05-26 | 2005-10-01 | Sociedad Española De Carburos Metalicos, S.A. | DUST MIXTURE FOR THERMAL PROJECTION, AND PROCEDURE FOR OBTAINING A COVERING AND COATING OBTAINED. |
| WO2010093612A1 (en) * | 2009-02-11 | 2010-08-19 | Greene, Tweed Of Delaware, Inc. | Thermal spray coated polymer substrates |
| DE102011052118A1 (en) * | 2011-07-25 | 2013-01-31 | Eckart Gmbh | Method for applying a coating to a substrate, coating and use of particles |
| JP6660116B2 (en) * | 2015-08-03 | 2020-03-04 | 東京応化工業株式会社 | Aqueous silane coupling agent, method for producing monomolecular film, and method for plating |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1305778A (en) * | 1970-08-04 | 1973-02-07 | ||
| GB1520184A (en) * | 1975-07-30 | 1978-08-02 | Metco Inc | Flame sprayable wires |
| CA1085239A (en) * | 1977-04-26 | 1980-09-09 | Vilnis Silins | Process for producing composite powder particles |
| JPS5923801A (en) * | 1982-07-28 | 1984-02-07 | Chisso Corp | Manufacture of magnetic metallic powder with superior oxidation resistance and dispersibility |
| JPS59208064A (en) * | 1983-05-11 | 1984-11-26 | Mitsubishi Electric Corp | Powder for flame spraying |
| US4849284A (en) * | 1987-02-17 | 1989-07-18 | Rogers Corporation | Electrical substrate material |
-
1990
- 1990-01-02 CA CA002006992A patent/CA2006992A1/en not_active Abandoned
- 1990-01-19 EP EP90101100A patent/EP0379995A1/en not_active Withdrawn
- 1990-01-20 CN CN90100379A patent/CN1044484A/en active Pending
- 1990-01-25 JP JP2013771A patent/JPH02232351A/en active Pending
- 1990-01-25 BR BR909000315A patent/BR9000315A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| JPH02232351A (en) | 1990-09-14 |
| CN1044484A (en) | 1990-08-08 |
| BR9000315A (en) | 1990-11-27 |
| EP0379995A1 (en) | 1990-08-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued | ||
| FZDE | Discontinued |
Effective date: 19920704 |