JPS60238469A - Flame spray material and manufacture of ceramic coating - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application: The present invention relates to a thermally sprayed modified zirconium material resulting in a coating 7 characterized by a low thermal conductivity and to a method for obtaining such a coating by thermal spraying.

Prior Art: Thermal spraying involves the thermal softening of heat-fusible materials, such as metals or ceramics, and the spraying of the softened material onto the surface to be coated. The heated particles are
They collide with surfaces and bond there. Conventional thermal spray guns are used for both particle heating and spraying purposes. In one type of thermal spray gun, the heat-fusible material is supplied to the gun in powder form. Such powders typically have, for example, a US standard sieve size of less than 100 mesh to about 5
It consists of particles with a small μ.

Thermal spray guns usually use flame or plasma spray to melt the powder bed particles. arise.

However, other heating devices can also be used, such as for example arc, resistance or induction heaters;
It will be recognized by those skilled in the art that bracket heating devices can be used alone or in combination with other types of heaters. In the case of a powder-type flame spray gun, the carrier gas for the powder can be one of the combustion gases, or it can be an inert gas, such as nitrogen, or it can simply be compressed air. can be. For plasma spray guns, the secondary plasma gas is typically nitrogen or argon. Hydrogen or helium is usually added to the secondary gas. The carrier gas is generally the same as the primary plasma gas, although other gases, such as hydrocarbon pilots, can be used in some cases.

The material can optionally be fed into the heating zone in the form of ronds or wires. For wire type thermal spray guns,
A rond or wire of material to be injected is fed into a heating zone formed by some type of flame, in which the material is melted or at least thermally softened and usually exposed to the injecting gas. and is therefore sprayed in fine powder form onto the surface to be coated. The ronds or wires can be formed by pultrusion or by sintering together with finely divided materials or organic binders or 1 m which disintegrate in the heat of a heating zone. The powder may be formed by bonding the finely divided materials together with a suitable binder and then discharging the material to be sprayed in finely divided form.

Sprayed ceramic coatings containing refractories, such as zirconium oxide, can be
? It is often used to protect the insulation layer of components. The zirconium oxide may contain some monomerized hafnium and (the remainder) impurities. Zirconium oxide is typically stabilized with calcium oxide or yttrium oxide or can be in the form of magnesium zirconate. Yttrium oxide is a powerful stabilizer because it provides long-term high temperature stability. Such zirconium oxide coatings are used, for example, for thermal insulation layers in gas turbine engines, where low thermal conductivity and heat resistance, heat corrosion resistance and erosion resistance are generally required.

Thermal sprayed ceramic coatings usually have some degree of porosity, typically up to about 20%, depending on composition, particle size distribution, spraying method and parameters, and are not completely dense. High porosity is generally attributed to lower thermal conductivity and higher thermal stress resistance than dense coatings. However, more porous coatings will have lower corrosion resistance, steam and infiltration resistance, as well as other abrasion conditions that exist in the environment in which such coatings are used.

No. 3,645,894 describes the plasma spraying of spherical agglomerate particles formed by spray drying certain binary and/or six component metal oxide powders. . The six-component particles are a metal oxide selected from the group consisting of a first metal oxide powder, a stabilized metal oxide powder, and nine types of oxides, each of which has a % ion conductivity under stable conditions. Consists of powder.

The first component can be zirconium oxide or thorium oxide, and the stabilizing oxide can be calcium oxide, yttrium oxide, ytterbium oxide, or a mixture of rare earth oxides. 9f
The group of oxides of class m broadly includes zinc oxide, but 2
18 cases include zinc oxide, which has more components than citrons, and there are only two items listed: zirconium oxide and one of the combinations with calcium. has a rather high concentration of zinc oxide.Other items include zirconium oxide and yttrium 14-oxide, as well as a combination with iron oxide of the fourth component of -i, which is substantially larger than zinc oxide. The combination described in U.S. Pat. It is taught that the method is particularly suitable for preparing powders.

Problem to be Solved by the Invention: From the foregoing description, the first object of the present invention is to obtain a new thermal spray material for producing ceramic coatings with low thermal conductivity properties. .

Another object of the present invention is to obtain new thermal spray materials for producing ceramic coatings having the combined properties of low thermal conductivity and high thermal shock resistance, thermal corrosion resistance and erosion resistance.

Another object of the present invention is to provide an improved thermal spraying process for producing ceramic coatings with low thermal conductivity properties.

Means for Solving the Problems: The above-mentioned aspects of the invention are solved by a thermally sprayed material for producing ceramic coatings characterized by low thermal conductivity.The thermally sprayed material according to the invention , zirconium oxide,
Consists of yttrium oxide, zinc oxide and optionally an organic binder.

Operation: According to the present invention, the ceramic composition is disclosed for spraying onto a substrate by a conventional thermal spraying device. Ta. Coatings produced by thermal spraying of the new ceramic compositions have a lower thermal conductivity7 compared to known thermally sprayed ceramic coatings. This dense coating of the .f1 product also has excellent erosion resistance, heat corrosion resistance, and thermal shock resistance.

The thermal spray material consists of a homogeneous ceramic composition having zirconium oxide, yttrium oxide, zinc oxide and optionally an organic binder in an amount up to about 10%. Yttrium oxide is present in an amount of about 2 to 40% by weight, preferably about 5 to 25% by weight, based on the total h1 of zirconium oxide, yttrium oxide and zinc oxide. Importantly, the zinc oxide should not exceed about 8% as it has been found that high bone results in an inferior coating Z that is soft, porous and weak.

The thermal spray material can be in any form suitable for, for example, rond spraying, but is preferably in powder form.

The powder has a conventional size range, generally about -100 mesh (
The size of the US standard sieve should have a mesh size of ~+5μ, preferably about -200 mesh ~+25μ.

The term "homogeneous" as used in this case in connection with thermal spray materials means that there are a large number of secondary particles of each individual oxide component forming the structure of the ceramic composition;
In this case the secondary particles have a size of less than 25μ, preferably 10μ.
less than In one embodiment, the components can be completely in solution together on a molecular scale. If the thermal spray material is a powder, the secondary particles of the individual components are substantially smaller than the average size of the powder particles, for example less than 1/3 of the average size.

The reason for the need for the composition to be homogeneous is that the crystal structure in sprayed ceramic coatings is significantly influenced by the chemical composition on a microscopic or rather molecular scale, and thus It is presumed that the reason is that the coating composition must contain all the oxide components in the coating solution at a certain level. For example, in order to form a powder of coated particles, the powder may be formed by simply bonding at least one component 7 onto the surface of an individually large core particle of another component (this powder is not homogeneous according to the invention), it is clear that the components coated on the surface do not diffuse sufficiently into the core particles during thermal spraying.

Homogeneous ceramic compositions can be formed by any known or desired method. For example, the powder can be prepared by conventional methods of fusing or sintering the six component oxides together and then crushing and sifting the fused product to form a powder of appropriate size. Another alternative method consists in bonding and sintering the secondary particles of zirconium oxide and the secondary particles of zirconium oxide, which have previously been stabilized with yttrium oxide in a conventional manner. One preferred method is to use 100% by weight, advantageously at least 0.2
Binding with organic binders that can be present in amounts of % by weight (
The present invention also involves secondary processing of powders in the form of composite particles containing a large number of secondary particles of each of the six oxide components. Such powders are available for example in the United States! It can be produced by a spray drying method as described in No. 1, No. 3,617,358. This U.S. patent 1
Any known or desired binder as described in the specification can be used. Generally, the binder is burnt off or evaporated from the powder in the heat of the thermal spraying process resulting in a coating that is free of binder components and has the desired properties of thermal shock resistance.

Another method of producing powders is to form composite particles using a spray dryer such as Ill.
The purpose is to feed the particles through the powder, fuse the particles, cool and solidify the particles 7 individually, and collect the powder particles thus formed. The high temperature zone can be generated with an induced plasma, and the powder can be fed in a conventional manner by means of a plasma spray gun. The collected powder, according to the invention, consists of homogeneous, solid, fused, substantially spherical particles.

The zirconium oxide component can be used in unstabilized form or can be stabilized with KN'dl-deutrethorium as described above. Additionally, even if not highly purified, tl + zirconium can typically have the same physical and chemical properties as monomerized hafnium, except for certain nuclear applications. Therefore, the physical properties of the film cannot be considered in Ohga's sense. Hafnium oxide is, for example, zirconium oxide and...
Up to about 10% by weight, based on the total amount of funium, can be present. The term "zirconium oxide" as used in this case and in the claims includes all zirconium oxides which can contain such proportions of .

Residue impurities can be present at up to about 11-m:%. However, if the oxide impurity is present in significant excess over this amount, the resulting
It has poor heat resistance and lacks striking properties. According to the present invention, 1,
, MshaP ++-]it of the film Δ formed with 11 products
Regarding acid and tapping that results in poor thermal shock resistance
− applies.

Although the homogeneous ceramic composition according to the invention is preferably used as is, the same composition can optionally be combined with other ceramic compositions or other thermally sprayed materials, such as metals. For example, if the material is a powder, the homogeneous ceramic I-1 composition can be blended with other thermally sprayed ceramic powders, such as aluminum oxide, that have the desired properties, such as wear resistance. Thermal sprayed coatings of such powder formulations will have a combination of erosion and thermal shock resistance properties. If the second powder is gold dust, the ceramic coating will be a cermet with properties 7 improved by the metal.

The coating according to the invention protects the surface from the effects of high temperatures;
It can be used wherever it is desired to form a thermal barrier layer for protection purposes, especially where conditions of erosion, hot corrosion or thermal shock are also present. Typical applications include gas turbine burner vessels, shrouds and other single-bin engine components. Other areas of application are rocket thrust chambers and nozzles, furnace chambers and exhaust pipes, fluidized bed coal gasifiers, power plant heat transfer surfaces, and piston domes, cylinder heads and cylinder walls of internal combustion engines, especially adiabatic diesel engines. be.

The coating according to the invention also has sliding wear properties Z and can be used, for example, on piston ring surfaces.

Example: Next, an example of climbing a tree will be explained in detail.

Example 1 Zirconium oxide (zr
o2) Powder 9875.9', particle size less than 5μ, average 1
908 g of yttrium oxide (Y20r5) powder with a particle size of 5 μ and an average of 0.6 zinc oxide (zno) 567
It was mixed with g. Dissolve the binder of sodium carboxymethyl cellulose in water to form a concentrated solution containing 113.5 F of binder and 4653.5 F of water and gold.

Slipke was formulated using the above adjusted concentrations in the proportions indicated where applicable according to the following table: Table 1 Total Additives Additive Weight of Solid Weight of Liquid 11.3
50g ceramic formulation 350g IL 1.135g binder solution at 10 g solids 113.5. ! i' 1,0
21.5. ! i'3, 632. V Water 3,632
When blending ingredients to form F-slip,
All liquids and solutions were first weighed into the mixing tank with the mixer running. The dry powder is then fed into a mixing tank so that deagglomeration occurs immediately, and after a short mixing time,
The slip became constant in consistency. This slip was spray dried as described in US Pat. No. 3,517,358. Heated air was introduced from the top of the vertical straight cylindrical drying chamber in a cyclone flow pattern. The slip was atomized and sprayed upward along the vertical center j'rs with compressed air.

The slip was fed by a pump into a pulverizing nozzle, from where it was injected through a drying chamber and finally collected as a dry powder in the chamber and a Nylon dust collector. The powder collected in the spray drying chamber was sieved through a 200 mesh sieve to yield a free-flowing powder with a particle size ranging from -200 mesh to +25 microns. , ;
Each composition contained 87% by weight of zirconium oxide, 8% by weight of yttrium oxide, and 5% by weight of zinc oxide, based on the total amount of oxides.
The weight was -.

Powder? MmTao Type 7 MB, described in U.S. Pat. No. 3,145,287 and under the trade name
A standard plasma spray spray gun of the general type sold by MITCO, Inc., Westbury, New York, under the name METCO Corporation (MITC, Inc.), Westbury, New York, is used and has a positive 2 powder port. G.H.
H) Thermal spraying was carried out using a nozzle and a powder feeder of the type described in US Pat. Parameters are pressure 71j10a
”(100p, s, i,) and velocity 2.4 @3/h
Argon plasma gas at r (800 FH), pressure 6.5 KP/cm" (50 p, θ, 1.) and flow rate Q, hydrogen secondary gas at 457 n3/hr (1507 H), 500 amps, 68 rut , carrier gas approx. 0
．． 45 m3/hr (1'5 ayH), powder supply rate of 2.72 Kp/hr (61 b/hr), and spray distance of approximately 7.62 cN&(!1 inch). The hardness of the coating was on average Re 37. Adhesion efficiency is approximately 50
%Met. Coatings up to about 0.32 m (about 1/8 inch) thick were applied to nickel alloy substrates prepared with a bond coat of aluminum coated nickel alloy powder sprayed as described in U.S. Pat. No. 3,322,515. Sprayed.

Metallographic examination of the coating showed the absence of unfused particles and a porosity of about 6 to 4 inches.

Example 2 The method of Example 1 was repeated, but the proportions of the oxide powders were adjusted so that the composition of the composite powder, 82.81 t% of zirconium oxide, 7.2 pAi% of yttrium oxide and 10% by weight of zinc oxide, was outside the scope of the invention. thing? occured. The coating was sprayed in a similar manner and the hardness of the coating was relatively low at approximately Rb 93.

Several coatings were prepared for comparison from commercially available powders. One such coating to be tested was prepared in the manner of Example 1, but without zinc oxide, using a composite powder of zirconium oxide and yttrium oxide of 20%. This powder is manufactured under the trademark METCO 202-NS by METCO, Inc., Westbury, New York.
) is sold under the name. Other commercially available products tested
Grieve, Trademark Metco (M1!!TOO) 204-N.
It was made from a pre-stabilized powder of 80% zirconium oxide and yttrium oxide, sold under the name Varnish (NS). These commercially available coatings are characterized for use on certain gas turbine engine components.

The thermal conductivity of the coating of this example and that of a similarly commercially available coating containing less than 5% zinc oxide were measured by a confirmation method using radar. For details, see Parker
Also, Journal'l of App'1ied Phys.
ics), Volume 62, Floor 9 (September 1961) F1a5h
Mθthodof DeterminingTherm
al Diffusivity, HeatOapac
l, ty and Thermal Conducti
vity)'. Briefly, a high-intensity, short-duration light pulse is absorbed into the front surface of a heated specimen several millimeters thick coated with camphor black, and measured by a crystallinity transition sensor generated at the back surface.
Record with an oscilloscope and camera.

Temperature diffusivity was measured by the shape of the temperature versus time curve at the back surface, and by the product of thermal conductivity, thermal capacity, temperature diffusivity, and density.

For thermal cycling testing, about 7 skins were deposited on a nickel alloy substrate prepared using the same punch as in Example 1.
It was sprayed to a thickness of 5 songs. The specimens were exposed to alternating collisions with flame, cold jets, and streams.

Hair formation is reported as the number of cycles or on the breakage points thus created.

Heat resistance was measured on the same specimen as it survived the flame/cold cycle. The remaining test piece was placed in a furnace for 10 minutes.
Heated to 00'O and then cooled 1F in water at room temperature. Results should be reported as the number of cycles for the failure point defined by the fracture.

In order to determine the tropism of a coating material for use in a gas turbine engine, for example, it was developed for erosion tests and skin corrosion tests. Mounted on a water-cooled specimen holder, the propane-oxygen burner ring 14 surrounding the abrasive supply nozzle was positioned for impingement onto the specimen.

-270 mesh ~ +15μ aluminum oxide abrasive? It was fed with a compressed air carrier gas at a flow rate of 6 no/sea through a 4.9 g diameter nozzle fire, resulting in a constant rate of abrasive delivery Y. The flame from the burner is approximately 980℃
produced a surface temperature of . The results of this test are expressed as coating capacity loss per unit time.

The results of said tests are listed in Table 1.

Table Example 1 Example 2 Porosity 6-4cm 10cm Flame/cold air jet (cycle test) 500, 40 (no destruction) (no destruction) Porosity 7% 7% Flame/cold air jet (cycle 212 500 test)・
(No destruction) (No destruction) The coating according to the present invention has 75
It also showed excellent resistance i to a molten mixture of sodium sulfate for 29 hours at 0°C.

Claims (1)

[Claims] 1. A thermal spray material characterized in that it is possible to obtain a coating with a low thermal conductivity, in which the homogeneous ceramic composition contains up to about 10% oxide based on the total weight of zirconium oxide and hafnium oxide. Zirconium oxide which may contain hafnium; yttrium oxide; zinc oxide; an organic binder which may be present in an amount up to about 1 oxide based on the ceramic composition; an amount up to about 1% by weight based on the ceramic composition yttrium oxide (zirconium oxide, hafnium oxide, yttrium oxide), based on the total weight of zirconium oxide and zinc oxide
and zinc oxide is present in an amount of about 1 to 8% based on the total weight of zirconium oxide, hafnium oxide, zinc oxide) . 2. The homogeneous ceramic composition is about -100 mesh to +5
Thermal spray material according to claim 1, in the form of a powder having a size μ. 3. The powder is in the form of composite particles consisting of a large number of secondary particles of zirconium oxide, yttrium oxide and zinc oxide, respectively, wherein the secondary particles have a size of less than about 25 microns. Thermal spray materials listed in section. 4. The thermal spray material of claim 6, wherein the secondary particles have a size of less than about 10 microns. 5. The thermal spray material of claim 6, wherein the secondary particles are combined with an organic binder in an amount of about 0.2 to 10% by weight of the composition. 6. The thermal spray material according to claim 3, wherein the composite particles are sintered. 1. Thermal spray material according to claim 2, wherein the powder is in the form of fused particles. 8. Large? Thermal sprayed part ψ with a length of 1200 mesh to +25μ
Unstable secondary particles of zirconium oxide in which the homogeneous ceramic composition contains up to about 10% by weight of hafnium oxide based on the total weight of zirconium oxide and hafnium oxide; : Secondary particles of lead oxide; about 0.52% for ceramic compositions
an organic binder in an amount of 1 to 10 parts by weight; and a residual impurity in an amount of about 1 part to 1 part by weight of the ceramic composition, wherein the secondary particles are less than about 10 microns in size. Has size t; E'l! Yttrium oxide is present in an amount of about 5-25% based on the total weight of zirconium oxide, liquefied hafnium oxide, yttrium oxide and zinc oxide; The thermal spray powder is present in an amount of about 2 to 6%. 9. A process for producing ceramic coatings by thermal spraying of thermally sprayed materials with low thermal conductivity, in which the homogeneous ceramic composition may contain up to about 10% hafnium oxide based on the total weight of zirconium oxide and hafnium oxide. Zirconium oxide; yttrium oxide; zinc oxide; an organic binder which may be in an amount up to about 10% by weight of the composition; and residual impurities in an amount up to about 1% by weight of the composition. the yttrium oxide is present in an amount of about 2 to 40 g, based on the total weight of the zirconium oxide, the liquefied hfnium, the yttrium oxide and the zinc oxide;
From about 1 to the total weight of yttrium oxide and zinc oxide
A method for producing a ceramic coating characterized in that it is present in an amount of 8. 10. The powder is in the form of composite particles consisting of a large number of secondary particles of each of zirconium oxide, yttrium oxide and zinc oxide, in which case the secondary particles are approximately 10μ
10. The method of claim 9, having a magnitude of less than 7.