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

Definitions

• 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.
• a simple technique for coating surfaces with metal or ceramic is by thermal (flame) spraying, employing either powder or wire.
• thermal spray When attempting to thermal spray onto plastic, however, special problems are encountered. Upon cooling, 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 being sprayed and lose its shape, or the plastic surface may burn or decompose.
• 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 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 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.
• spray technique is somewhat critical causing variation in results, and further improvement in bonding and cohesive strengths has been in demand.
• 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 discloses thermal spray coating materials comprising a high temperature plastic and a metal.
• a silicon aluminum powder blended with poly(para-oxybenzoyl)ester in accordance with Example 1 of the patent has been highly successful 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.
• U.S. Patent No. 3,617,358 discloses spray drying to produce thermal spray 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.
• U.S. Patent No. 4,593,007 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 agents such as described in a text book "Silane Coupling Agents" by E.P. Plueddemann (1982 Plenum Press, New York NY), for example Chapter 1(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 plastic bonding powder, and to produce an improved abradable coating.
• a thermal spray powder formed of a polymeric constituent and a mineral 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.
• 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 formed from a precursor silane having a hydrolyzable group bondable to the mineral constituent upon hydrolyzing of the hydrolyzable group.
• the polymeric constituent also has a silane layer thereon and may comprise, for example, a poly(para-­oxybenzoyl)ester or an epoxy.
• 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.
• 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 manufacturing process, and by thermal spraying the powder formed thereby.
• 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 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.
• the mineral contains silicon.
• 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 glass such as 3Al2O32SiO2 (mullite), BaO2SiO2, BaOAl2O3SiO2, BaOTiO2SiO2, 2CaOSiO2, Cr2O3SiO2, Er2O3SiO2, ZrO2SiO2 (zircon), 2MgOSiO2, ZrOZrO2SiO2; or a silicon alloy of aluminum, bronze, nickel, cobalt or iron.
• silicate or glass such as 3Al2O32SiO2 (mullite), BaO2SiO2, BaOAl2O3SiO2, BaOTiO2SiO2, 2CaOSiO2, Cr2O3SiO2, Er2O3SiO2, Z
• 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.
• 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).
• the powder is in the conventional size range, vis. -147 +5 microns, preferably -88 +44 microns or alternatively -44 +5 microns.
• the powder is a simple blend of a mineral powder and a polymeric powder, as distinguished from a composite powder.
• 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.
• the proportion of plastic to mineral should generally be in the range of 5% to 95% by volume, and preferably 5% to 25%.
• each powder particle has a coating layer thereon comprising an organofunctional silane.
• 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 silane will yield optimum coupling if it has a monolayer coverage 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.
• 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.
• the mineral powder contain silicon as described above.
• the mineral contains silica for example as glass.
• silicon per se or as a silicide or in alloy form is suitable, because 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.
• 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 slurry.
• the steam is turned on to drive off the water. Once the powder is dry and free flowing it is removed and screened. Alternatively, only the mineral powder is so treated, and the plastic powder is blended in afterward.
• the steam pot drying of the powder is at sufficiently low temperature so as not to cure the plastic constituent or the silane with respect to it.
• the thermal spraying step which melts or at least surface heat softens the powder constituents effects the appropriate heat treatment to achieve excellent bonding and coating cohesion, 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 spray 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 U.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 No. 4,416,321 (Browning).
• a blend of 40% by weight (56% by volume) of a high temperature aromatic polyester plastic, poly(para-oxybenzoly)ester, sold under the trade name of EKONOL 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 silicon-aluminium 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 slurry. The steam is turned on to drive off the water and dry the powder. Once the powder is free flowing it is removed and screening 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, #2 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 Type 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 Hysol 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.
• 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.
• 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 results are effected.
• Example 1 is repeated using a different silane, namely glycidoxypropyltrimethoxysilane, in 99% by weight (99% by volume) water. Similar results are effected.
• 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.
• a bond coat of nickel aluminide is used for this purpose of coating onto a metal surface. An excellent, abradable, cohesive coating results.
• Example 1 is 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.

Landscapes

• 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)

Applications Claiming Priority (2)

Publications (1)

Family

ID=23168629

Family Applications (1)

Country Status (5)

Cited By (3)

Families Citing this family (3)

Citations (6)

• 1990
  • 1990-01-02 CA CA002006992A patent/CA2006992A1/fr not_active Abandoned
  • 1990-01-19 EP EP90101100A patent/EP0379995A1/fr not_active Withdrawn
  • 1990-01-20 CN CN90100379A patent/CN1044484A/zh active Pending
  • 1990-01-25 JP JP2013771A patent/JPH02232351A/ja active Pending
  • 1990-01-25 BR BR909000315A patent/BR9000315A/pt unknown

Patent Citations (6)

Non-Patent Citations (2)

Also Published As

Similar Documents

Legal Events