FR2638156A1 - ARTICLE COMPRISING A PROTECTIVE COATING AND PREPARATION METHOD - Google Patents

Abstract

A coating system such as a thermal barrier system 14 uses a surface 12 of substrate to which a specific roughness has been given, to constitute a bonding and attachment surface for the coating. The surface is characterized by the fact that it has cavities with a shredded profile which extend in the substrate 10 over at least 15 mm, on arithmetic average. The roughness of the surface of the substrate is preferably obtained by electrochemical machining or chemical attack. The material of the substrate 10 may consist of a superalloy and the material of the coating 14 may consist of zirconium oxide stabilized with another oxide.

Description

ARTICLE COMPRISING A PROTECTIVE COATING

AND PREPARATION PROCESS

  The invention relates to protective coatings for metallic manufactured articles which are exposed to high temperature environments. It relates more particularly to ceramic coatings, for example in a coating system acting as a thermal barrier, which do not require a coating layer of

  bond between the ceramic layer and the metal substrate.

  The combination of the properties of ceramics with the properties of metals, in particular superalloys,

  has been the subject of considerable scientific research.

  According to one aspect of this research, attempts have been made to obtain manufactured metallic articles comprising coatings

  protective ceramics, in order to combine the properties

  ceramic ceramic tees with ductility and resistance

  mechanical tance of metals. Ceramic coatings with low thermal conductivity behave like thermal barriers which isolate and protect the underlying metal substrates from the high temperatures and / or oxidizing conditions to which the substrates are

  exposed. Due to these properties, bar coatings

  are particularly useful for protecting

  metal components of equipment such as mo-

  gas turbine generators and generators. In applications

  aircraft engine, the use of ceramic coatings on high pressure turbine fairings, and

  thermal barrier coatings on other components.

  engines, is a fundamental aspect of evolution in

  course aimed at obtaining tur-

  higher bine, increased thrust / mass ratios and better specific fuel consumption. The applica-

  tion of such coatings on the metal members above

  peralloys commonly used in combustion chambers of aircraft engines, transition conduits, jackets of afterburners, blade bases and aerodynamic surfaces in various stages, both reduces the temperature of the metal substrate and the

  effects of thermal transients on the latter.

  In the past, coatings have often been applied

  thermal barrier ceramics by spraying techniques

  plasma or vapor deposition. To per-

  put the adhesion of the ceramic layer on the metal substrate, it was generally necessary to use a transition coating layer, or superposed bonding layer,

  which is a layer that fozmeentre metal and ceramic.

  When applying the bonding coating layer to the

  metal trat, it provides protection against oxidation for the metal substrate and a relatively rough layer in which the ceramic particles are arranged

  so as to form a mechanical bond with the metal substrate

  tal. Among the tie coating layer compositions

  commonly used, the class of materials is shown

  excavator of MCrAly alloys. Such alloys generally have

  a composition which comprises 5 to 40% of chromium, 3 to 25% of aluminum

  minimum, 0.01 to 3% yttrium (or hafnium, lanthanum, cerium or scandium), and a complement, M, selected from

  the group comprising iron, cobalt, nickel and metals

  swaddles of these. Thermal barrier coating systems using these types of tie coating layers are well known in the art, and are described, for example, in U.S. patents. following: 4,055,705,

4,248,940, 4,405,660 and 4,485,151.

  However, the use of a coating layer

  bonding in the thermal barrier coating system

  that limits the temperature to which the ar

  coated manufactured article. Many of the materials used for a bonding coating layer cannot withstand a temperature above about 1040 C, while the ceramic layer and the metal substrate can

  withstand significantly higher temperatures. By con-

  sequent, in the use of such a manufactured item re-

  clothed, the temperature of the bonding coating layer limits the maximum operating temperature of the system

  thermal barrier coating. In addition, such a cost-

  Che overlapping bond coating increases the weight of

  finished manufactured items. The increased weight that is assigned

  drinkable at the bond coating layer is a consideration

  large ration, especially for applications such as

  aircraft engines. The inclusion of a layer of

  bond coating in the bar coating system

  Thermal production also requires additional manufacturing operations, which increases manufacturing costs and lengthens production sequences. In addition, the bonding coating layer is likely to degrade and to reveal defects which can in turn cause chipping, chipping or cracking of the

  ceramic layer which is fixed on it.

  The object of the present invention is therefore to provide a thermal barrier coating system which does not require

  not the type of tie or transition layer described above

  above, between the metal substrate and the ceramic coating

thermal barrier.

  The invention also aims to provide a system

  a thermal barrier coating which is capable of

  withstand higher temperatures than was possible

  sible so far for thermal barrier systems

  using such bonding coating layers.

  Yet another object of the invention is to provide

  a process for directly applying ceramic coatings

  thermal barrier mics on metal substrates, without the use of transition or bonding layers.

  According to one aspect of the invention, a manufac-

  ground on which a protective coating is formed, such as a thermal barrier coating, comprises a metal substrate having at least one surface roughened, in

  which are formed cavities with a shredded profile,

  linked to each other on the surface, which extend into the

  substrate over at least 15 µm, arithmetic average. A re-

  ceramic thermal barrier garment is fixed on the surface so that at least part of the coating is located in the cavities of the rough surface of the substrate, on the interface or connection line between them. In one

  embodiment, the substrate consists of a dry material

  selected from the group which includes nickel-based, cobalt-based and iron-based alloys, and the ceramic coating consists essentially of zirconium oxide

stabilized with another oxide.

  According to another aspect of the invention, a method

  for coating a metal substrate with a protective coating

  such as a thermal barrier material, includes

  the operation of roughening at least one surface

  this of the metal substrate, so that the measurement of the area

  this result with a profile measuring device gives a value of at least about 15 μm, on arithmetic average. A convenient and preferred technique for roughening the surface is selected from the chemical etching, electrochemical etching and laser surface treatment techniques. A coating is then applied to the substrate

  protective such as a ceramic barrier coating

  mique, so that at least part of the coating is inside the cavities of the rough surface of the

  substrate. The coating can be applied to the ru-

  substrate by employing various methods, such as, for example, plasma spraying, vapor deposition or sputtering. To obtain a stoichiometric composition of the ceramic, the thermal barrier coating can be heated in an oxygen-containing atmosphere. The invention will be better understood on reading the

  description which follows of embodiments, given at

  title of nonlimiting examples. The rest of the description

  refers to the appended drawings in which: FIG. 1 is an enlarged partial section which schematically represents the metnlographic structize of part of a coated manufactured article in accordance with an embodiment of the invention; Figure 2 is an exploded perspective view which schematically shows a manufactured item which

  must apply a thermal barrier coating,

  ment to another embodiment of the invention; and

  FIG. 3 is a perspective view which represents

  schematically the appearance of a manufactured article coated with a thermal barrier, in accordance with the invention, which has

  been subjected to a thermal cycle test.

  Figure 1 shows schematically a section with a magnification of about 32 of a part of a metallic article which carries a ceramic barrier coating

  durable thermal, according to the invention. The metal substrate-

  lique 10 has at least one rough surface 12 on the

  which is fixed a ceramic thermal barrier coating 14. The coating 14 is formed on the substrate 10 so

  at least part of the coating 14 is in direct contact

  rect with the rough surface 12. According to the invention,

  the measurement of the profile of the rough surface 12 with an apparatus

  profile measurement reil gives a value of at least 15 μm, in arithmetic mean, and this surface is characterized by the fact that it has cavities with a jagged profile,

as shown in figure 1.

  The substrate 10 can have a wide variety of

  structures. In general, the substrate 10 can be constituted

  titrated by any metallic structure which benefits from an adherent coating as a coating establishing a

  thermal barrier. In a particular embodiment-

  mentally useful, substrate 10 is an article suitable for

  use in structures with mechanical resistance

  high nique and high resistance to temperature and corrosion. In such an embodiment, the substrate 10

  includes a base material selected from the group cons-

  titrated by alloys based on nickel, based on cobalt and

  based on iron. We find in this group of material the

  alloys known as superalloys because of their exceptional properties at elevated temperatures. For gas turbine engine applications, it

  It is often desirable that the material chosen for the sub-

  trat 10 has high mechanical strength, as well as -

  good resistance to oxidation and corrosion at temperatures--

  high erasures. Table 1 below gives a list of

  typical alloy positions which have such characteristics

artistic.

  The material that is chosen for the ceramic coating

  that 14 must have among other properties, a low

  thermal conductivity, suitable adhesion to the

  trat 10 for resistance to flaking and cracking under the effect of thermal stresses, a thermal expansion rate as close as possible to that of the substrate 10, and an appropriate stabilization of the crystal structure of the ceramic, to minimize the effects of dilation

  in volume resulting from a structural transformation.

  Zirconium oxide is often used in thermal barrier coating systems because it provides an effective thermal barrier. We found that

TABLE 1

SUPER ALLOY COMPOSITIONS

  Nominal percentage by weight, plus accidental impurities A1Loy Fe Cr AI Ti Y203 Ni C Co Mo W Cb Ta Re Iif B Zr Y

MA956 * 20 4.5 0, 5 0, S

  Ma754 1 20 0.3 0.5 0.6 * 0 05os René N4 9.3 3.7 4.2 * 7 5 1, S5 6 0, S 4 René NS 7 6.2 * 0, tOS 7.5 1.5 5 615 3 0.15 40ppu lOOppr René 80 14 3 5 * 0t17 9.5 4 4 4015 0.03 MAR-M-509 22t5 10 0t 6 * 7 3.5 0S5 Note: * = complement to 1OO ' 4 N Do CO oo Lu o '

  to obtain excellent stability, zirconium oxide -

  must consist of mixtures of cubic phases and

  tetragonal. It has also been established that stabilization by-

  Zirconium oxide with another oxide, such as yttrium oxide, produces this desired phase mixture. The ceramic coating 14 preferably consists of partially stabilized zirconium oxide with between about 6% and% by weight of yttrium oxide. A proportion lower than

  about 6% by weight of yttrium oxide does not produce the sta-

  partial mobilization desired. On the contrary, a proportion greater than about 20% by weight of yttrium oxide results in a total stabilization of the zirconium oxide. In many thermal barrier coating applications, it is preferable to use between about 6% and about 8%

by weight of yttrium oxide.

  During initial assessments of this in-

  It has been found that the degree of surface roughness and the character of the roughness, in combination, are of unexpected importance in the ability of the superimposed ceramic coating to be mechanically fixed firmly on a rough substrate. It has been noted that bond coatings, such as that of the MCrAlY type deposited by thermal spraying, have a surface roughness in the range of about 11.5-14

  pm, arithmetic mean. Ceramic coatings on

  perposed presented good grip on such an over-

  face during long cycles of thermal tests. However, in the absence of such a bonding or transition layer, a surface roughness in lower ranges led to an unsatisfactory bond. For example, sanding a surface generally gives a surface roughness in the

  range of about 25-6.5 pm, arithmetic average.

  Given the nature of the surface, it has been recognized that in addition to a relatively high degree of roughness, measured for example by a profile measuring device, the surface must

  have a "jagged" configuration, as shown in the figure

  gure 1, to allow a good connection or mechanical fixing

  between the rough surface and a ceramic coating

  perposed. For example, a surface that has been treated or rendered

  rough by EDM machining, which is a techni-

  that well known, which has been the subject of numerous descriptions and which is widely used, presented a roughness

  surface area of about 19 pm on arithmetic average. However

  less, tests have shown that large cracks

  floated along its connecting line with a ceramic coating. This is believed to result from the state of the layer

recast on the rough surface.

  Rather, a surface that has been roughened by electrochemical machining, which is also a technique

  well known, which has been the subject of numerous descriptions and

  which is widely used for renovating materials

  but which is not specially designed to render a surface

  this rough, presented a surface roughness in the range

  from 15 -25 pm (arithmetic average), and did not appear-

  be no cracks at the level of the connection line, in the same test. In accordance with the invention, a attributes such results to the surface comprising jagged structures similar to teeth, shown in FIG. 1, as well as to a surface roughness of the monk. Approximately 15 μm (in

arithmetic average).

  The data in Table 2 below are representative

  results of tests obtained in the evaluation of the

vention.

TABLE 2

  Cyclic thermal tests with the JETS device (2000 cycles) (Upper ceramic: ZrO2 - 8Y203, 130 pm thick) Example Sample Preparation Roughness of Surface surface results (d) (pm in arithmetic mean)

  1 Standard Layer 11.5 - 14 No cracking

  (a) safe link on the link line

  2 No seams - Machining 15 - 24 No seams

  che de liai- electro- sures on its (b) chemical connection line 3 No neck- Electro- 19 Cracks che de liai --- significant erosion

sound (b) on the li-

gene of liai-

  sound 4 No sanding 2.5 - 6.5 Cracks che of liiai- important

sound (c) on the li-

gene of liai-

  sound (a) CoNiCrAlY bonding layer (130 pm) / René 80 alloy substrate (b) Substrate: MA956 alloy roughened (brazed on a René 80 buttress) 1 1 (c) Substrate: René 80 alloy (d) Periodic microscopic examination with a magnification of In Table 2 as well as in Table 3 which follows, the cyclic thermal tests were carried out by means of a thermal shock device for reactors called Jet Engine Thermal Shock (JETS), designed and constructed by the plaintiff, and described in the document MACH 3 Magazine, March / September 1987, published by GE Aircraft Engines,

  Production Operation, "Ceramic Tough New Breed of Shroud".

  The JETS device basically has four sections:

  (1) a heating / cooling structure, (2) a sup-

  wearing of samples under test on a vertical carousel, (3) an electronic stepper motor control and indexing device, and (4) measuring and control equipment. An oxygen-propane torch allows rapid heating (in about 20 seconds) of the ceramic face, on button-type samples of 2.5 cm in diameter. The

  next station subjects the samples to cooling

  fast (in about 20 seconds up to a temperature below 260 C} between air jets which are projected both on the ceramic surface and on the metal support. The temperatures on both sides are measured

with optical pyrometers.

  In the evaluations which are represented by the data of Tables 2 and 3, the ceramic thermal barrier coating in ZrO2 stabilized with 8% by weight of Y203 was formed by air plasma spraying to the thicknesses indicated. In each cycle of the Table

  2, each sample was heated under the following conditions

  Vantes: average temperature of the ceramic surface: 1221 C; average temperature of the metal rear face: 868 C; average temperature difference: 353 C. Then,

  for each cycle, the sample was cooled to a tem-

Z638156

  temperature below about 260 C, as described above.

TABLE 3

  Cyclic thermal tests with the JETS device (2500 cycles) (Upper ceramic: ZrO2 - 8Y203; average thickness: 915-1165 pm) Example Sample Preparation Surface roughness of surface area (c) (pm in arithmetic average) Standard Layer of 11 , 5 - 14 No fis- (a) secure connection on the connection line

  6 - No neck - Electro - 18 - 24 No crack

  sure bonding on its (b) the bonding line (a) CoNiCrAlY bonding layer (130 Wm) / René 80 alloy substrate (b) Substrate: MA956 alloy roughened (brazed on a René 80 alloy buttress (c) Periodic microscopic examination with a magnification of

50

  During each cycle in Table 3, each sample was heated under the following conditions: average temperature of the ceramic surface: 1408 C; average temperature of the metal rear face: 653 C; average temperature difference: 755 C. Then, in each cycle, the sample was cooled to a temperature

  below about 2600C, as described above.

  Comparison of the data in Table 2 and the Ta-

  bleau 3 clearly shows the extremely important effect of the invention on the integrity of the coating: the combination of the degree of surface roughness and the nature of this surface.

  gosity can provide a significant thermal barrier system

  incredibly improved for high temperature applications

  ture. In a particular example using the alloy

  René N5 for the substrate, we used an attack operation

  than chemical to roughen the surface of the sample.

  Such a method for roughening the surface is particularly

  particularly interesting for a material of this type which is a

  monocrystalline alloy whose nominal composition is indi-

  shown in Table 1. The chemical attack resulted in a roughness

  surface sity in the range of about 15 -20 pm (average-

  arithmetic), with a depth of attack of 50 to 100 pm. In addition, such an attack technique can benefit from the difference in chemical composition and attack characteristics between dendrites and the interdendritic region.

  alloys such as René N5. The acid attack has pro-

  produces a rough surface (up to 20 Pm on average arithmetic-

  particularly well adapted tick for receiving and

  expensive a top layer of ceramic coating. In addition, dendrite tips that extend inside the ceramic coating can have some effect on the

  formation of cracks inside the ceramic,

  thus curating a mechanism of relaxation or attenuation of

  constraints near the interface. We can get results

  similar states, depending on the article which constitutes the substrate, by adjusting the parameters of the well-known electrochemical machining process, which is generally used to remove significant quantities of metal, to shape

the surface of an article.

  In the chemical attack example above, doing

  use the René N5 alloy, we used for the

  tackles an aqueous solution consisting predominantly of HC1, with a small amount of HNO3, and containing FeC13

  in the proportion of about 50% by weight of FeCl3 relative to

  port in the water. The attack was carried out for approximately one

  hour near room temperature.

  For applications where it is desired

  table, the manufactured article coated with the invention-may further comprise one or more pre-formed structures

  ceramic, each pre-formed structure being mechanically fixed

  only on at least one surface of the metal substrate, in the manner which is illustrated in FIG. 2. The pre-formed ceramic structure can be produced so as to have a predetermined shape and thickness, and this thickness can significantly exceed the thickness that can be reached

  easily for ceramic coatings formed by spraying

  rization by plasma in air. In the particular embodiment which is represented in FIG. 2, the pre-formed structure comprises a ceramic plate 16 comprising a pair of retaining grooves 18 formed along slices

  opposite of the plate 16. Means for fixing me-

  typically the plate 16 on the surface 22 of the substrate 10 comprises a pair of retaining tabs 20 which are associated with the retaining grooves 18, with the retaining tabs 20 arranged so that each tab 20 is

  locked with one of the retaining grooves 18. The lans

  retaining plates 20 are formed integrally with the substrate 10 and have a configuration provided so as to retain in position the ceramic plate 16, relative to the substrate 10. The remaining surfaces of the substrate 10, like the surfaces 24 , 26, 28 and 30, can consist of

  roughened surfaces, which can be applied

  plaster a ceramic coating, in the way that is illus-

  trée by the surface 12 and the coating 14 in Figure 1.

  In such an embodiment, the ceramic coating of

  thermal barrier can be formed to encapsulate

  fully the substrate 10, and it can be constituted by sections having several different thicknesses;

  Bar coating systems can be formed

  thermal insulation described above without using an intermediate bonding coating layer formed on site,

  between the protective ceramic and the underlying structure.

  According to the invention, a method of coating a metal substrate with a thermal barrier material comprises the operations which consist in roughening the

  minus one surface of the metal substrate, as described above

* above, and apply a ceramic thermal barrier coating to it. The ceramic coating is applied so that at least part of it is located inside the shredded profile cavities which are formed in the

  rough surface of the substrate. The operation is carried out

  to make the surface rough so that the measurement of the profile of the rough surface of the substrate with a profile measuring device gives a value of at least 15 μm,

  arithmetic mean, preferably between 15 and 25 qm.

  There are a number of techniques that can be used

  different to roughen the surface of the substrate. Con-

  according to the invention, it has been found that electro-

  chemical and chemical attack are two special processes

  highly effective in producing a rough substrate surface.

  beggar. In the material removal technique, a goal of

  electrochemical machining is to produce a finish of.

  smooth surface. For example, it is commonly used. electrochemical machining in the manufacture of engine components

  aircraft to meet sur- face finish requirements

  face which are imposed by design considerations

  mechanical and aerodynamic. However, we have found,

  mement to the invention, that by modifying parameters of pro-

  such as the intensity, the stroke of the piston, the flow rate of the nozzle and the electrolyte solution, it is also possible to use the electro-chemical machine to produce a rough metal surface of the type which is suitable for a bonding surface in the barrier ceramic coatings

  thermal. For example, electrochemical machining was used

  only to produce surface roughness corresponding to values measured with a profile measuring device

  which are in the range of 18 to 25 pm, on average arithmetic-

  that for substrates of metallic alloys having the alloy compositions MA 956 and MA 754 which are indicated

  in Table 1. The resulting rough metal surfaces

  your were characterized by ridges and valleys

  tinctures and presented a rough and grainy texture, if-

  milaire to the textures presented by layers of coating-

  bonding elements formed by plasma spraying in

the air.

  Similar rough surfaces can be produced

  by a chemical attack treatment. By choosing to

  appropriate lesson the attack solution and the duration during the

  which the substrate is immersed in this solution, as described above in relation to the alloy René N5, one can obtain a variety of surface roughness desired. -We have for example obtained surface roughness corresponding to values between approximately 15 and 23 μm, on arithmetic mean, measured with a profile measuring device, by etching a substrate of metal alloys having the compositions of the René N4 alloys and

  René N5 which are indicated in Table 1.

  For substrates that are formed by techniques

  metal molding, it may be desirable to form the rough substrate surface as part of the operation

  molding. The step of increasing roughness, consistent

  In accordance with the invention, can be accomplished during the formation of the metal substrate, by casting the substrate into a mold which itself has a rough surface, the rough surface of the mold having a configuration designed to give a

  rough surface corresponding to the raw molding substrate.

  One can for example make rough surfaces selection-

  molded by wax using knurling, etching or electrochemical machining techniques. Once the rough surfaces of the mold have been made, normal lost-wax molding techniques can be used to form

  the substrate. The structure of the substrate resulting from gross

  the age comprises at least a surface part having a nature

  re and a roughness suitable, in accordance with the invention, to function as a bonding surface for a coating

thermal barrier ceramic.

  The ceramic thermal barrier coating can

  be applied by a number of processes on the

  rough surface of the substrate. Suitable techniques include plasma spraying, vapor deposition and sputtering. All of these techniques are good

  known and have been the subject of numerous descriptions. Of

  generally speaking, in plasma spraying,

  powder cules having the desired composition are transported

  shot from a plasma gun to the surface of the target by a jet of hot gas. The powder particles are heated to a state of fusion by the jet of hot gas and they

  re-solidify upon deposition on the target surface.

  In the vapor deposition, the article to be coated is placed

  above a molten bath of a material having the composition

  desired position. As the material evaporates, the resulting vapor condenses on the article and forms a coating on the article. The vapor deposition process is conveniently carried out in a vacuum chamber, and an electron beam is often used as a heat source to keep the heated material in the molten state. For thermal barrier coatings containing oxides, the ceramic deposited resulting from the techniques

  application above may be oxygen deficient.

  When such coatings are used in the process of the invention, the thermal barrier coating can be further treated by heating

  in an oxygen-containing atmosphere, so that

  hold a practically stoichiometric ceramic composition

  stick. For partial zirconium oxide ceramics-

  Slowly stabilized, heating the coating in air for about 4 hours at a temperature of about 1080 "C

  is generally sufficient. It should be noted that in some

  nes applications, the coated article is annealed under the conditions of use, in which case the annealing operation

  at high temperature described above is not necessary.

  In some bar coatings applications

  thermal insulation, the desired thickness of the ceramic coating

  can exceed the thickness that can easily be obtained in -

  using ceramic coating formation techniques

  as described above. In such applications, the pro-

  assigned of the invention may further comprise the meta-

  kinetics of at least one pre-formed structure of a ceramic material, on at least one surface of the metal substrate,

  as described above in relation to Figure 2.

  Of course, as a preparatory operation

  for any of the processing techniques that

  Within the scope of the invention, it may be desirable to thoroughly clean the surface which is to be roughened or coated. You can remove dirt,

  fats, oxides, etc., by a number of processes

  suitable cleaning dice known in the art.

  In another evaluation of the invention, it was re-

  clad with a thermal barrier material, in accordance with the invention, an alloy structure MA 956, known in

  the technique of aircraft engines under the name "taste-

  in V "shape, and this structure was tested in an apparatus corresponding to a burner of the" flame tunnel "type, with cyclic temperature variation. The interior surface of the two sides was roughened by electrochemical machining

  back of the V-shaped gutter, and we applied on the

  rough faces, by air plasma spraying, a ceramic coating 0.5 mm thick, consisting of zirconium oxide stabilized by 8% by weight of ytrietum oxide. The coated V-shaped gutter structure was subjected to a thermal cycle test in a flame tunnel tester, which produced higher operating temperatures than the thermal shock tester used in the examples. above, and which includes a pressure heating system. During the heating part of the test cycle, the sample is heated by a flame produced by self-ignition of pressurized jet fuel, at a pressure of about 7 x 105 Pa above atmospheric pressure, to a temperature of about 1260 C, in a duration of 22.5 seconds. During the cooling cycle, water cooling was used to cool the sample to a pressure of 6 x 105 Pa

  above the atmospheric pressure, up to a temperature

  ture of around 1040 C, over the same duration of 22.5 seconds.

  The thermal barrier coated sample successfully underwent 1000 of these test cycles with the burner. The thermal barrier coating system remained completely intact, with no apparent chipping of the ceramic. The roughened surface by electrochemical machining again provided an excellent bonding surface for the adhesion of the ceramic to the metal substrate. Figure 3 shows the appearance of the V-shaped gutter after 1000 thermal cycles. Rough surfaces

  by electrochemical machining on which the coating

  ramic has been applied, are shown in Figure 3

  as interior surfaces 44 and 46 of the rear panels

  re 40 and 42. During the test, two small cracks,

  signed by Zeferences 48 and 50 in Figure 3, appeared in the rear edges of the gutter structure

  in V. Each crack measured approximately 8 mm in length.

  and was located approximately in the middle area of the respective back pan. These cracks were probably

  due to the relatively high temperature gradient that exists

  was on both sides of the sections during the temperature cycles. During the test, the V-shaped gutter was held firmly in position. by two end plates of V-shaped gutter. The end plates were mounted in the test apparatus and the complete apparatus was locked

  in the water pipe, in such a way that the return water

  cooling gives the end flanges, therefore the

  upper and lower ties of the V-shaped gutter, a tem-

  temperature much lower than that of the middle region of the pan. The resulting thermal gradient over the extent of each

  pan induced maximum thermal stress in its part

  middle tie, and probably led to the formation of cracks 48 and 50 which are shown in Figure 3. It should also be noted that this V-shaped gutter structure

  simulates an organ in the afterburner of a mo-

  aircraft, and it is considered that this structure is faulty only if it is completely cut into two separate pieces. Theoretically, when the cracks 48 and propagate towards the nose before 52 df the V-shaped gutter, the thermal gradient and the resulting thermal stress on the extent of each pan will decrease to a level

  such that each crack stops spreading or developing

lopper further.

  We have described in the foregoing a system of re-

  thermal barrier clothing which does not require the formation of a bonding coating layer between the substrate

  metal and ceramic thermal barrier coating.

  The invention provides an article of manufacture, protected to the point

  from a thermal point of view, which includes a ceramic coating of-

  maple which is firmly bonded to the substrate. By eliminating the

  the need for such a bond coating layer, the

  vention provides a finished item that is lighter and

  can - withstand higher operating temperatures

  than was possible until now, using

  conventional thermal barrier coating systems.

  In addition, by providing a method for directly applying ceramic thermal barrier coatings to metal substrates, the invention also reduces costs.

  and the length of the manufacturing sequences.

  Although the invention has been described in detail in

  flattering some of his preferred embodiments, those skilled in the art can make many changes

  and modifications. For example, although the information has been described

  When considering several specific examples, the

  ceramic and metal compositions, as well as

  processing methods which are indicated in the description,

  should be considered as non-limiting examples.

Claims (19)

  1. Manufactured article comprising a protective coating (14) on an article metallic substrate (10), characterized in that the metallic substrate has a surface (12) in which cavities with shredded profile are formed which extend in the substrate on at least   pm (arithmetic mean), and these cavities are rac-   strung to each other on the surface.   2. Article according to claim 1, characterized in that the coating (14) is a ceramic coating   which is formed in the cavities, so as to establish an ac-   mechanical hooking between the surface (12) and the coating ceramic (14).   3. Article according to claim 2, characterized in that the ceramic coating (14) is a thermal barrier coating which is based essentially on zirconium oxide.   4. Article according to claim 3, characterized in that the substrate (10) is a superalloy based on at least one element selected from the group formed by Ni, Co and Fe; the cavities extend into the substrate (10) in the range of about 15-25 µm (arithmetic average); and the thermal barrier coating (14Ai consists predominantly of zirconium oxide stabilized with another oxide.   5. Article according to claim 4, characterized in that the substrate (10) consists of a superalloy with   nickel-based single crystal structure; and put it on   The thermal barrier (14) consists predominantly   zirconium oxide stabilized with approximately 6 to 20% by weight of yttrium oxide.   6. Article according to claim 4, characterized   in that the thermal barrier coating (14) is suitable   pleated with a thickness of about 0.13 mm.   7. Article according to claim 6, characterized in that the coating (14) is applied with a thickness   in the range of about 0.13-1.3 mm.   8. Article according to claim 1, characterized in that it comprises: the metal substrate (10); at least one structure pre-formed from a ceramic material (16); and means (18, 20) for fixing the pre-formed structure to the article. 9. Method for preparing an article metallic substrate (10) for applying a protective coating   (14), characterized in that it comprises the operation consisting   both to give the substrate a surface (12) having cavities with a shredded profile which extend in the substrate (10) over at least 15 μm (on arithmetic average), so that   the cavities are connected to each other at the surface.   - 10. A method of applying a protective coating (14) on a metal substrate (10), characterized in that it comprises the following operations: a surface (12) of the substrate is roughened to form in the surface of the cavities which have a jagged profile and which extend   in the substrate (10) over at least 15 mm (on average arith-   metic), the cavities being connected to each other at the surface; and the protective coating (14) is formed in the   cavities, so that the covering is mechanically hooked   only to the substrate (10) at the level of the cavities.   11. The method of claim 10 for the application   cation of the protective coating (14) on the metal substrate   lique (10), characterized in that the surface is roughened by a metal removal process selected from the group which includes electrochemical removal, etching chemical and laser attack.   12. The method of claim 10, for the app-   plication of the protective coating (14) on a metallic substrate   molded metal (10) 'characterized in that the surface is roughened by forming the cavities in the substrate (10) by   precision molding at the time of substrate molding.   13. The method of claim 10 for the avpli-   cation of a ceramic coating (14) on a substrate (10) consisting of a superalloy based on at least one element   selected from the group comprising Ni, Co and Fe, charac-   terized in that it comprises the following operations: a surface (12) of the substrate (10) is roughened, to form in the surface cavities which have a jagged profile and which extend in the substrate over a range of 15 at 25 pm   (arithmetic average); and we form the ceramic coating   mique (14) in the cavities so that the coating is   mechanically attached to the substrate (10) at the cavities your.   14. The method of claim 13 for the application   cation of a ceramic thermal barrier coating (14) on a substrate (10) consisting of a nickel-based superalloy, characterized in that the surface is roughened by a metal removal process which is selected from the group including electrochemical removal,   chemical attack and laser attack.   15. Method according to claim 13, characterized   in that the ceramic coating (14) is formed by a pro-   assigned coating application which is selected in   the group comprising vapor deposition, pulp deposition   plasma verification and sputtering.   16. The method of claim 14, characterized in that the thermal barrier coating (14) consists predominantly of zirconium oxide; and the surface   is roughened by electrochemical removal.   17. The method of claim 14, characterized in that the thermal barrier coating (14) consists predominantly of zirconium oxide; and the surface   is roughened by chemical attack.   18. The method of claim 14, for the app-   plication of a ceramic thermal barrier coating (14) on a monocrystalline substrate of nickel-based alloy (10), characterized in that the surface is roughened by chemical attack; and the ceramic thermal barrier coating (14) consists predominantly   into a stabilized zirconium oxide.   19. The method of claim 18, characterized in that the thermal barrier coating. (14) consists predominantly of zirconium oxide stabilized with   about 6 to 20% by weight of yttrium oxide.