CA2126538A1

CA2126538A1 - Thermal barrier coating and method of depositing the same on combustion chamber component surfaces

Info

Publication number: CA2126538A1
Application number: CA002126538A
Authority: CA
Inventors: David C. Giles; Roger E. Begin; David R. Dugger; Eric W. Paskvan
Original assignee: Detroit Diesel Corp
Current assignee: Detroit Diesel Corp
Priority date: 1994-06-22
Filing date: 1994-06-22
Publication date: 1995-12-23

Abstract

A thermal barrier coating and method of depositing the same on the surfaces of combustion chamber components in compression-ignition internal combustion engines is disclosed. The thermal barrier coating is a dual layer having a first metallic layer comprised of MCrAlY material deposited on the component surface. A porous ceramic layer comprised of Yttria partially stabilized zirconia or Ceria-Yttria partially stabilized zirconia is deposited on the metallic layer to impede the flow of heat therethrough. In operation, the metallic layer creates a mechanical bond between the component surface and the ceramic layer, allows for a smooth transition between the differing physicalproperties of the component and the ceramic layer and serves as a corrosion barrier by protecting the component from combustion gases and contaminants.
There is further disclosed a method of depositing the thermal barrier coating comprising the steps of (1) chemically treating the component surface to remove dirt and oil; (2) grit blasting the treated component surface to roughen the surface and increase the available surface area for deposition; (3) plasma spray depositing a metallic layer comprised of MCrAlY material on the roughened component surface to a thickness between 0.003-0.006 inches; and (4) depositing a porous ceramic material comprised of 10 %-15 % volume porosity Yttria partially stabilized zirconia or 10 %-15 % volume porosity Ceria-Yttria partially stabilized zirconia on the metallic layer to impede the flow ofheat therethrough.

Description

21265~

., --1 'l'H ~ MAI, BARRIER COATING AND METHOD
OF DEPOSll~G 'l'H~ SA~ E ON
COMBUSTION CHAMBER COMPONENT SURFACES

Technical Field This invention relates generally to thermal barrier coatingfi applied to the surfaces of metallic componentfi in internal combustion engines. In particular, and more specifically, the invention relates to ceramic-refractory coatings and a process of applying the same to the surfaces of combustion chamber components in compression ignition internal combustion engines.

BackPround Art Heat-insulating structures and heat-insulating coatinqs, i.e. thermal barrier coatings have been employed by those skilled in the art to enhance the thermal efficiency of internal combustion engines by permitting more complete fuel burning at higher temperatures. Typically, such heat-insulating coatings have been applied to all of the chamber surfaces, includinq the cylinder wall and head and piston combustion face to prevent heat loss.

Heat-insulating structures and heat-insulating coatings have also been used in automobile exhaust systems to maintain high exhaust temperatures required by thermal reactors and catalytic converters and to impede the emission of unburned hydrocarbons emitted into the atmosphere as an undesirable component of exhaust gas.

- 2126S~8 -In previous attempts to increase thermal efficiency, heat-in6ulating structures and heat-lnuul~tlng coatlng~ such as ceramic plate6 and ceramic coatlngs, reupectlvely, have been applied to component ~urfaces. Significantly, such ceramic coatings function not only as heat insulation barriers but also exhibit advantageous physical characteri~tics such as providing a hard, corrosive resi6tant, and abrasive resistant surface.

Typical of ceramic materials commercially available include a cerium-yttrium zirconium oxide material as described in U.S. Patent No. 4,599,270, available the Perkin-Elmer Corporation.

The above ceramic materials were developed princlpally for application to high speed turbine blades, such as used in commercial aircraft, turbo jet engine6. Typically, these blades are made of nickel-based superalloy, high strength steel materials and the environment is one in which the blades, thus the ceramic linlng on the blades, is ~ub~ected to high temperatures at relatively constant, non-cyclical, compressive loads.

Prior art literature describing the use of ceramic materials for these applications and techniques for applying the ceramic lining are shown in more detail in ~.S. Patent Nos. 4,273,824; 4,332,618; 4,335,190;
4,880,614; and 4,916,022.

The need or demand for such a heat insulating barrier in internal combustion engines, and particularly two and four cycle compression-ignition (diesel) engines, has only recently come to be realized. Recent engine designs, and the modification of pre-existing engine designs, has included increasing the power output demands for a cubic inch di~placement of the engine's power capaclty. Such de~ign6 have resulted in higher compression ratios and exhaust gas temperatures. Not only i6 it important to keep the exhaust gas temperatures from reaching the cylinder head and related components, thus reducing the cooling requirements and other engine design requirements, the heat of the exhaust gas is being used to increase the engine efficiency by recirculating it through the intake air ports.

However, experience has shown that the ceramic coatings and techniques for application to apparatus such as gas turbine engine blades, previously referenced, is not ideal for application to the surfaces of combu6tion chamber components in compression-ignition internal combustion engines, where (i) the substrate materials including the cylinder head and piston may be cast iron, (ii) the materials of the related components such as the exhaust valves may be aluminum alloyed high temperature steel or metallic based alloy, and (iii) the temperatures in the combustion chamber and at the combustion chamber surfaces are extremely high.

Prevlously known ccramlc coatings and technlques ~or depo~lting the same are even less ideal for 2-cycle compression-ignition internal combustion engines such as applicant's Series 149 engine which utilizes a pot-type cast iron cylinder head. In applicants' Series 149 engine design, the temperatures in the combustion chamber are even greater than in conventional internal combustion engines, since every stroke of the piston i5 a combustion stroke. For example, temperatllres in the combustion chamber may vary 2126~28 between 150 to 1400. Similarly, temperatures at the combustion chamber surfaces cyclically range from about 150 when being freshly charged with intake air to about 1500 at combustion. All of these factors contri~ute to the requirement for new materials and techniques in accordance with the present invention.

Prior disclosures include those shown in U.S.
Patent Nos. 3,9~1,890, 3,976,809 and 3,911,891 for coating pi~ton heads and 4, 077, 637 for coating piston rings, as well as 4,254,621 for ceramically coating any of the combustion chamber surfaces including the cylinder head. However, none of these is considered to serve the purposes of the present invention in providing an extremely cost effective and efficient dual layer ceramic lining and application technique for lining the combustion chamber 6urfaces of a compression-ignition internal combustion engine expanded to the above-mentioned operating condltions.

Summary Of The Invention It is an object of the present invention to provide a protective coating for application to the surfaces of combustion chamber components exposed to cycllcal temperatures and compression loads.

It is another object of the invention to provide a thermal barrier coating comprised in part of a ceramic refractory material for application to the internal 6urfaces of combustion chamber components, including the cylinder head, exhaust valves and piston heads. A6 more fully set forth herein, the thermal barrier coatlng 1~ capable of provlding ~ood adherence to the material~ and heat insulation properties in an 21265~8 environment where the temperatures cyclically range from 150F to 1400F in the compression chamber, 150 to 1500F at the combustion chamber surfaces and where the compressive loads on the coating may be as high as 2500 pounds per square inch.

It ifi a further object of the invention to provide a thermal barrier coating which is economical, and readily adaptable to being deposited on a metal substrate by means of plasma spray vapor deposition.

Yet another object of the invention is to provide a method of depositing a thermal barrier coating on the surfaces of combustion chamber components, including the cylinder heads, exhaust valves and piston heads, which is economical and reliable.

A more specific object of the present invention is to provide a dual layer thermal barrier coating for the surfaces of the combustion chamber components in a compression ignition internal combustion engine. In accordance with the present invention, the thermal barrier coating comprises a metallic layer deposited on the component surface and a ceramic layer deposited on the metallic layer to impede the flow of heat therethrough. The metallic layer creates a mechanical bond between the component surface and the ceramic layer, allows for a smooth transition between differing physical properties of the component and the ceramic layer and serves as a corrosion barrier by protecting the component from combustion gases and contaminants.

It is yet another specific ob;ect of the pre~ent invention to provide a method of depositing a 212653~

dual layer thermal barrier coating on the surfaces of combustion chamber components in a compression-ignition internal combustion engine. In accordance with the present invention, the component surface should first be grit bla6ted to eliminate oxides and roughen the surface to increase the available surface area for deposition.
A metallic layer is then deposited on the component surface to protect the component from corrosion caused by combustion gases and contaminants. Finally, a porous ceramic layer is deposited on the metallic layer to impede the flow of heat therethrough.

These and other objects and advantages of the present invention will be more obvious and apparent with reference to the drawings and detailed description of the invention which follows.

~rief Description Of The Drawings FIGURE 1 is an enlarged cross-sectional view of a pi6ton dome illustrating the metallic and ceramic layer6 of the thermal barrier coating of the present invention applied to the face;

FIGURE 2 i~ a plan view of a Series 149 pot-type cylinder head utilized in 2-cycle compression-ignition internal combustion engines manufactured by applicant and shown with the thermal barrier coating of the present invention applied thereto; and FIGURE 3 is a block diagram view of the method ~teps of the pre6ent invention.

2126~
-Best Mode For Carryinp Out The Invention Re~errlng to Figures 1 and 2, the present invention is directed to a dual-layer protective coating and a method of applying the coating to the surfaces of component6 which form the chambers of internal combustion engines. In Figure 1, there is shown a piston dome generally designated by reference numeral lo as u6ed by applicant in its hiqh output, Series 149 compression ignition internal combustion engines.
Figure 2 shows the protective coatinq of the preset invention as applied to applicant's Series 149 pot-type cylinder head. ~oth components shown in Figures l and

2 are constructed of cast iron for conventional ~pecifications.

Aithough the use of thermal barrier coatings is known ~n the art, particularly the aerospace i~dustry, previous desiqns and methods of ap~lication have proved inefficient and in many cases inoperable.
In the case of compre6fiion-ignition internal combustion engines, and particularly 2-cycle compression-ignition engines, 5pallations i.e., the flaking of ceramic materials due to poor adhesion caused by thermal fatigue is recognized as the primary failure mode observed in the applicakion of ceramic coatings to component surfaces.

In an effort to overcome the inefficiency and inoperability of known protective linings, applicant has developed a dual layer protective lining and method of applying the ~ame to the surfaces of combustion chamber components ln compre~ion-ignition internal combustion englneB a8 more fully described herein.

2126~8 Still referring to Figure 1, there is shown a thin metallic layer 14 deposited on the component curface 12 to protect the component from corrosion cau~ed by combustion gases and contaminants. In the case of piston domes, as in ~igure 1, it is recognized that the component surface must initially be machined back (~hown generally by reference numeral 11) to the specified coating thickness to retain the proper compression ratio. Metallic layer 14 is preferably deposited to a thickness between 0.003 - 0.006 inches and is comprised of a MCrAlY material selected from the group consisting of nickel base alloy (NiCrAlY), cobalt ba~ed alloy (CoCrAlY), nickel cobalt base alloy (NiCoCrAlY), and iron base alloy (FeCrAlY).

Still referring to Figure 1, there is shown a porous ceramic layer 16 deposited on the metallic layer 14. Ceramic layer 16 is preferably deposited to a thicknes~ between 0.010 - 0.015 inches and i6 comprised of material having between 10-15 percent volume porosity. More particularly, ceramic layer 16 may be comprls~d of yttrium partlally stabllized zirconia or ceria-yttrium partially stabilized zirconia. In the former case, applicant has found it preferable that the ceramic layer be comprised of eight percent yttrium partially 6tabilized zirconia.

Metallic layer 14 referenced above in the dual layer thermal barrier coating of the present invention is recognized as creating a mechanical bond between the component ~urface 12 and ceramic layer 16. ~etallic layer 14 al~o allows for a smooth transition between the differing physical properties of the component, in this case piston dome 10 and ceramic layer 16. More specifically, metallic layer 14 exhibits a thermal expansion characteri6tic which relieves stresses that might otherwise be created at elevated operating temperature~.

As referenced above, metallic layer (bond coat) 14 is preferably comprised of a MCrAlY alloy.
Such alloys have a broad composition of 17.0-23.0 percent chromium, 4.5-11.0 percent aluminum, 0.5-1.20 percent yttria, 0.0-0.20 percent iron, with M being the balance, 6elected from the group consisting of iron, cobalt, nickel, and mixtures thereof. Minor amounts of other alloys such as silicon may also be present. Such alloys are known in the prior art for use alone as a protective coating and are described in various U.S.
patents, including U.S. Patent Nos. 3,542,530;
~,676,085; 3,754,903; 3,928,026; 4,005,989; 4,055,705;
4,339,509; 4,743,514; 4,880,614; and 4,916,022.

Still referring to Figures 1 and 2, it is preferred that the MCrAlY layer be applied by plasma spray deposition. However, other deposition processes may be employed ~or producing the MCrAlY layer ~ including, for example, sputtering flame spray and electron beam vapor deposition 60 long as a thin, uniform thickness, hiqh integrity coating of the desired composition results.

Ceramic layer 16 which is deposited on metallic layer 14 is also subject to a broad composition of yttrium partially stabilized zirconia or cerium-yttrium partially stabilized zirconia. Applicant has found that in the former case, it is preferred to have a percentage of between 7.0-9.0 percent yttrium with trace constituent6 of other elements including 0.0-1.5 per~ent S102, 0.0-0.5 percent CaO, 0.0-0.8 percent MgO, 21~6~3~
...

0.0-0.4 percent Fe203, 0.0-0.2 percent Al203, and 0.0-0.2 percent TlO2, with 2rO2 being the balance. As in the case af the metallic layer 14, ceramic layer 16 is also preferably deposited by plasma spray deposition.
However, other deposition processes may be employed such as ~putterlng, flame spray and electron beam vapor depofiition~

As referenced above, it is preferable that metallic layer 14 have a thickness between 0.003-0.006 inches and the ceramic layer 16 have a thickness between 0.010 and 0.015 inche6 for a combined total thickne6s between 0. 013 and 0.021 inches. It is also preferable that ceramic layer 16 be comprised of a porous material having between 10-15 percent volume porosity. It is al~o preferable that particles which make-up the metallic and ceramic layers have a spherical morphology.

Referring now to Figure 2, there is shown the protective coating of the present invention as applied to component surfaCe6 of applicants' Series 149 pot-type cylinder head used ln 2-cycle compression ignitlon internal combustion engines. In the pot-type design, a separate cylinder head 18 is used to encase each combustion chamber. Thus, each cylinder head 18 encases 4 exhaust valves 20.

As shown in Figure 2, the metallic and ceramic layers, 14 and 16 are deposited only on the component surfaces such as valve heads (combustion faces) 22, and fire deck 24 which are exposed surface6 in the combustion chamber. Conventional masking techniques may be u~ed to prevent the deposition of the metallic and cernmic coatings, 14 and 16 on non-combustion 6urfaces 2126~8 26. Surfaces 26 are recognized as contacting the engine block and fall outside the combustion chamber.

It i6 anticipated that the thermal barrier coating of the present invention will be applied to the surface6 of combustion chamber components in newly manufactured engine6. However, 6ignificant after market work can also be performed to repair, for example, cylinder heads and other components. Such repair work should include the deposition of the thermal barrier coating disclosed herein.

Referrlng now to Figure 3, there is disclosed detailed method steps for depositing the thermal barrier coating of the pre6ent invention on component surfaces in compres6ion-ignition internal combustion engines. As set forth above, it i6 recogni2ed that in the case of certain components, such as piston domes, the component mu6t initially be machined back to the specified coating in order to retain the proper compression ratio. The component surface must then be prepared by chemically treating lt to remove dirt and oil. Prefera~ly, a suitable vapor degreasing apparatus utilizing for example, perchlorethylene is utilized.

Following cleaning, the component surface is grit bla~ted in order to roughen the surface, eliminate oxides and increase the available surface area for deposition. The component surface 12 is grit blasted using, for example, an aluminum oxide grit to achieve an optimum 6urface roughness between 150-300 ~in AA.

Significantly, applicant has found that ~urface roughnesses le~s than the optimum range re~erenced above are in~ufflclent to form a lasting 21265~

mechanical bond with metallic layer 14 when exposed to cyclical temperatures and compression loads such as those exhibited by 2-cycle compression ignition internal combustion engines. Applicant has further found that fiurface roughne~es greater than the optimum range cauaes ~urface component peaks to actually fold over one another and break off thus reducing the availa~le surface area and adhesion properties of the metallic layer.

Still referring to Figure 3, a thin metallic layer 14 i~ then deposlted on the roughened component surface. As referenced above, the metallic layer i~
preferably comprised of MCrAlY material and is selected from the group consisting of nickel base alloy (NiCrAlY), cobalt ba5ed alloy (CoCrAlY), nickel cobalt base alloy (NiCoCrAlY), and iron base alloy (FeCrAlY) in accordance with the percentage weights of the preferred embodiment referenced above. The metallic layer i5 deposited to a thickness between 0.003-0.006 inches at an average application rate per pass less than 0.001 inches and preferably between 0.004-0.007 inches.

The metallic layer 14 is deposited directly to the component surface 10 preferably by plasma spray vapor deposition at a spray distance ~etween 3~ - 5 inches. In this regard, applicant has found that distances greater than the desired range result in unmelted or partially melted particles deposited on the substrate. As a result, the porosity and oxide content of the metallic layer 14 is increased and the density of the metalllc layer 14 is decreased. As an aside, it ~hould be recognlzed that it is preferred to avoid oxidation and to decrea~e oxide content-to obtain a better mechanical bond between the metallic layer 14 and 21~

the roughened component surface 12. Thus, components should be stored in hot, humidity-free environments between grit blasting and the application of the metallic bond coat 14 to avoid such oxidation.

Still referring to Figure 3, a porous ceramic layer 16 i6 then deposited atop the metallic layer 14 to impede the flow of heat therethrough. If applied properly, the ceramic layer 16 will not exhibit any deviations such as bumps or waves across the surface contour of the component. The ceramic layer 16 will similarly be void of spalling, cracks and blisters.
Applicants have found that chips on most ceramic coated parts cannot extend more than 0.2~ inches away from the edge nor be proud to the edge surface. Edge chipping is not acceptable, however, on piston domes.

As referenced above, the ceramic layer is preferably comprised of material having 10-15 percent volume porosity and comprised of 7-9 percent yttrium partially 5tabili2ed zirconia or ceria yttrium partially ~tabilized zirconia according to the compositions of the preferred embodiments referenced above.

In the typlcal applicat~on, the ceramic layer 16 18 depoBited on the metallic l~yer 14 by the u~e of a plasma spray gun. ~efore the respective coatings, the ceramic and the metallic materials prefera~ly exist as tiny spheroids. Typically, such powders are free flowing spherical alloys, manufactured by inert gas atomization. These particals are melted in the plasma gun and adhere to the component surface 12 or metallic surface 14, respectively. ~ecause the plasma spray interacts wlth air molecules, the metallic and ceramic co&tings 14 and 16 are porous. The degree of porosity, - æl26s38 however, can be adjusted by varying the stand off torch distance, i.e., plasma spray distance.

The ceramic layer is preferably deposited to a thickness between 0.010-0.015 inches at an average application rate per pass les6 than 0.001 inches and more preferably in the range of 0.004-0.007 inches at a spray difitance between 3~ - 5 inches. For verification purposes, the proper thickness of both the ceramic layer 16 and the metallic layer 14 can be confirmed using a permascope or a tinsley gauge. Similarly, compositional requirements may be confirmed by using a 6canning electron microscope.

In contrast to the results of varying the spray di~tance during the deposition of the metallic layer, applicant has found that spray distances closer than the optimum range result in increased density and decreased porosity which, in turn, inhibits adhesion of the ceramic layer 16 to the metallic layer 14.

Slmilarly, the utilization of spray distances greater than the optimum range result in increased porosity and decreased structural integrity of the coatlng. Under such conditions, the thermal barrier coating has been found to fall during thermal cycling resultlng in spallatlons.

It is recognized that the metallic and ceramic layers may be applied by other deposition means, including electron beam vapor deposition, sputtering, chemical vapor deposition, powder flame spray applicatlon and detonatlon gun application. Typical methods of plasma-fipray coatings are more thoroughly set forth in the publication "Plasma-Spray Coatings", 21265~

ScIENTIFIc A~ERICAN, September 19~8, Herbert Herman, the teachings of which are expressly incorporated herein.

While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.

Claims

What Is Claimed Is:

1. In a compression ignition internal combustion engine, a thermal barrier coating for the surfaces of the combustion chamber components, comprising:
a metallic layer having a thickness between .003 - .006 inches deposited on the component surface;
and a ceramic layer having a thickness between .010 - .015 inches and a volume porosity of 10 - 15 percent deposited on the metallic layer to impede the flow of heat therethrough, wherein the metallic layer creates a mechanical bond between the component surface and the ceramic layer, allows for a smooth transition between the differing physical properties of the component and the ceramic layer and serves as a corrosion barrier by protecting the component from combustion gases and contaminants.

2. A thermal barrier coating as in claim 1, wherein the metallic layer is comprised of MCrAlY
material.

3. A thermal barrier coating as in claim 2, wherein the MCrAlY material is selected from the group consisting of nickel base alloy (NiCrAlY), cobalt base alloy (CoCrAlY), nickel cobalt base alloy (NiCoCrAlY) and iron base alloy (FeCrAlY).

4. A thermal barrier coating as in claim 1, wherein the ceramic layer is comprised of Yttria partially stabilized zirconia.

5. A thermal barrier coating as in claim 4, wherein the ceramic layer is comprised of eight percent Yttria partially stabilized zirconia.

6. A thermal barrier coating as in claim 1, wherein the ceramic layer is comprised of Ceria-Yttria partially stabilized zirconia.

7. A thermal barrier coating as in claim 1, wherein the ceramic layer is comprised essentially of the following materials by percentage weight:
7.0 - 9.0 wt % Y2O3 0.0 - 1.5 wt % SlO2 0.0 - 0.5 wt % CaO
0.0 - 0.8 wt % MgO
0.0 - 0.4 wt % Fe2O3 0.0 - 0.2 wt % Al2O3 0.0 - 0.2 wt % TiO2 Balance ZrO2

8. A thermal barrier coating as in claim 1, wherein the metallic layer is comprised essentially of the following materials br percentage weight:
17.0 - 23.0 wt % Chromium 4.5 - 11.0 wt % Aluminum 0.5 - 1.20 wt % Y
0.0 - 0.20 wt % Iron Balance Nickel

9. A thermal barrier coating as in claim 1, wherein the metallic layer is comprised of particles having a spherical morphology.

10. A thermal barrier coating as in claim 1, wherein the ceramic layer is comprised of particles having a spherical morphology.

11. In an internal combustion engine, a thermal barrier coating for the surfaces of the combustion chamber components, comprising:
a metallic layer consisting essentially of MCrAlY material where Cr is present in an amount from 17 to 23% by weight, Al is present in an amount from 4.5 to 11.0% by weight, Y is present in an amount from 0.5 to 1.20% by weight, Fe is present in an amount from 0.0 to 0.20% by weight and M is the balance where M is selected from Ni, Co, NiCo, and Fe, the metallic layer having a thickness between .003 - .006 inches and deposited on the component surface; and a porous ceramic layer having a volume porosity of 10 - 15% and thickness between .010 and .015 inches, comprised of Yttria partially stabilized zirconia deposited on the metallic layer to impede the flow of heat therethrough, wherein the metallic layer creates a mechanical bond between the component surface and the ceramic layer, allows for a smooth transition between the differing physical properties of the component and the ceramic layer and serves as a corrosion barrier by protecting the component from combustion gases and contaminants.

12. In an internal combustion engine, a thermal barrier coating for the surfaces of the combustion chamber components, comprising:
a metallic layer consisting essentially of MCrAlY material where Cr is present in an amount from 17 to 23% by weight, Al is present in an amount from 4.5 to 11.0% by weight, Y is present in an amount from 0.5 to 1.20% by weight, Fe is present in an amount from 0.0 to 0.20% by weight and M is the balance where M is selected from Ni, Co, NiCo, and Fe, the metallic layer having a thickness between .003 - .006 inches and deposited on the component surface; and a porous ceramic layer having a volume porosity of 10 - 15% and thickness between .010 and .015 inches, comprised of Ceria-Yttria partially stabilized zirconia deposited on the metallic layer to impede the flow of heat therethrough, wherein the metallic layer creates a mechanical bond between the component surface and the ceramic layer, allows for a smooth transition between the differing physical properties of the component and the ceramic layer and serves as a corrosion barrier by protecting the component from combustion gases and contaminants

13. A thermal barrier coating as in claim 11, wherein the ceramic layer is comprised of eight percent Yttria partially stabilized zirconia.

14. A thermal barrier as in claims 11 or 12, wherein the ceramic layer is comprised essentially of the following materials by percentage weight:
7.0 - 9.0 wt % Y2O3 0.0 - 1.5 wt % SiO2 0.0 - 0.5 wt % CaO
0.0 - 0.8 wt % MgO
0.0 - 0.4 wt % Fe2O3 0.0 - 0.2 wt % Al2O3 0.0 - 0.2 wt % TiO2 Balance ZrO2

15. A thermal barrier coating as in claims 11 or 12, wherein the metallic layer is comprised of particles having a spherical morphology.

16. A thermal barrier coating as in claims 11 or 12, wherein the ceramic layer is comprised of particles having a spherical morphology.

17. A method of depositing a thermal barrier coating on the surfaces of combustion chamber components in an internal combustion engine, comprising the steps of:
depositing a metallic layer having a thickness between .003 - .006 inches on the component surface to protect the component from corrosion caused by combustion gases and contaminants; and depositing a ceramic layer having a thickness between .010 - .015 inches and a volume porosity of 10 -15 percent on the metallic layer to impede the flow of heat therethrough.

18. The method of claim 17 further comprising the step of:
grit blasting the component surface to eliminate oxides and roughen the surface to increase the available surface area for deposition.

19. A method of depositing a thermal barrier coating on the surfaces of combustion chamber components in a compression ignition internal combustion engine, comprising the steps of:
chemically treating the component surface to remove dirt and oil;
grit blasting the treated component surface to roughen the surface and increase the available surface area for deposition;
plasma spray depositing a thin metallic layer comprised of MCrAlY material on the roughened component surface;
plasma spray depositing a porous ceramic layer comprised of Yttria partially stabilized zirconia on the metallic layer to impede the flow of heat therethrough, wherein the metallic layer creates a mechanical bond between the component surface and the ceramic layer, allows for a smooth transition between the differing physical properties of the component and the ceramic layer and serves as a corrosion barrier by protecting the component from combustion gases and contaminants.

20. A method of depositing a thermal barrier coating on the surfaces of combustion chamber components in a compression ignition internal combustion engine, comprising the steps of:
chemically treating the component surface to remove dirt and oil;
grit blasting the treated component surface to roughen the surface and increase the available surface area for deposition;
plasma spray depositing a thin metallic layer comprised of MCrAlY material on the roughened component surface; and plasma spray depositing a porous ceramic layer comprised of Ceria-Yttria partially stabilized zirconia on the metallic layer to impede the flow of heat therethrough, wherein the metallic layer creates a mechanical bond between the component surface and the ceramic layer, allows for a smooth transition between the differing physical properties of the component and the ceramic layer and serves as a corrosion barrier by protecting the component from combustion gases and contaminants.

21. A method of depositing a thermal barrier coating as in claim 18, wherein the ceramic layer is comprised of eight percent Yttria partially stabilized zirconia.

22. A method of depositing a thermal barrier coating as in claims 19 or 20, wherein the MCrAlY
material is selected from the group consisting of nickel base alloy (NiCrAlY), cobalt base alloy (CoCrAlY), nickel cobalt base alloy (NiCoCrAlY) and iron base alloy (FeCrAlY).

23. A method of depositing a thermal barrier coating as in claims 19 or 20, wherein the ceramic layer is comprised of material having between 10-15 percent volume porosity.

24. A method of depositing a thermal barrier coating as in claims 19 or 20, wherein the ceramic layer is comprised essentially of the following materials by percentage weight:
7.0 - 9.0 wt % Yttria 0.0 - 1.5 wt % Silica 0.0 - 0.5 wt % CaO
0.0 - 0.8 wt % MgO
0.0 - 0.4 wt % Fe2O
0.0 - 0.2 wt % Al2O
0.0 - 0.2 wt % Ti2O
Balance ZrO2

25. A method of depositing a thermal barrier coating as in claims 19 or 20, wherein the metallic layer is comprised essentially of the following materials by percentage weight:
21.0 - 23.0 wt % Chromium 4.5 - 11.0 wt % Aluminum 0.5 - 1.20 wt % Yttrium 0.0 - 0.20 wt % Iron Balance Nickel

26. A method of depositing a thermal barrier coating as in claims 19 or 20, wherein the metallic layer is comprised of particles having a spherical morphology.

27. A method of depositing a thermal barrier coating as in claims 19 or 20, wherein the ceramic layer is comprised of particles having a spherical morphology.

28. A method of depositing a thermal barrier coating as in claims 19 or 20, wherein the metallic and ceramic layers have a combined thickness between 0.01 -0.021 inches.

29. A method of depositing a thermal barrier coating as in claims 19 or 20, wherein the metallic layer has a thickness between 0.003 - 0.006 inches.

30. A method of depositing a thermal barrier coating as in claims 19 or 20, wherein the ceramic layer has a thickness between 0.010 - 0.015 inches.

31. A method of depositing a thermal barrier coating as in claims 19 or 20, wherein said component surfaces are grit blasted to obtain a surface roughness between 150 - 300 µin AA

32. A method of depositing a thermal harrier coating as in claims 19 or 20, wherein the metallic layer is deposited at a spray distance of 3 - 5 inches.

33. A method of depositing a thermal barrier coating as in claims 19 or 20, wherein the ceramic layer is deposited at a spray distance of 3 - 5 inches.

34. A method of depositing a thermal barrier coating as in claims 19 or 20, wherein the metallic layer is deposited at an average application rate per pass between 0.0004 - 0.0007 inches.

35. A method of depositing a thermal barrier coating as in claims 19 or 20, wherein the ceramic layer is deposited at an average application rate per pass between 0.0004 - 0.0007 inches.

36. A method of depositing a thermal barrier coating as in claims 19 or 20, wherein the metallic layer is deposited at an average application rate per pass less than 0.001 inches.

37. A method of depositing a thermal barrier coating as in claims 19 or 20, wherein the ceramic layer is deposited at an average application rate per pass less than 0.001 inches.

38. A method of depositing a thermal barrier coating on the surfaces of combustion chamber components in a 2-cycle compression ignition internal combustion engine, comprising the steps of:
chemically treating the component surface to remove dirt and oil;
grit blasting the component surface to obtain a surface roughness of 150 - 300 µinch AA to eliminate oxides and increase the available surface area for deposition;
plasma spray depositing a metallic layer on the component surface to protect the component from corrosion caused by combustion gases and contaminants, the metallic layer deposited to a thickness between 0.003 - 0.006 inches at an average application rate per pass less than 0.001 inches and at a spray distance between 3 - 5 inches;
plasma spray depositing a ceramic layer on the metallic layer to impede the flaw of heat therethrough, the ceramic layer comprised of material having between 10-15 percent volume porosity and deposited to a thickness between 0.010 - 0.015 inches at an average application rate per pass less than 0.001 inches and at a spray distance between 3 - 5 inches, wherein the metallic layer creates a mechanical bond between the component surface and the ceramic layer and allows for a smooth transition between the differing physical properties of the component and the ceramic layer.

39. A method of depositing a thermal barrier coating as in claim 38, wherein the MCrAlY material is selected from the group consisting of nickel base alloy (NiCrAlY), cobalt base alloy (CoCrAlY), nickel cobalt base alloy (NiCoCrAlY) and iron base alloy (FeCrAlY).

40. A method of depositing a thermal barrier coating as in claim 38, wherein the ceramic layer is comprised of Yttria partially stabilized zirconia.

41. A method of depositing a thermal barrier coating as in claim 38, wherein the ceramic layer is comprised of eight percent Yttria partially stabilized zirconia.

42. A method of depositing a thermal barrier coating as in claim 38, wherein the ceramic layer is comprised of Ceria-Yttria partially stabilized zirconia.

43. A method of depositing a thermal barrier coating as in claim 38, wherein the ceramic layer is comprised essentially of the following materials by percentage weight:
7.0 - 9.0 wt % Y2O3 0.0 - 1.5 wt % SiO2 0.0 - 0.5 wt % CaO
0.0 - 0.8 wt % MgO
0.0 - 0.4 wt % Fe2O
0.0 - 0.2 wt % Al2O
0.0 - 0.2 wt % Ti2O
Balance ZrO2

44. A method of depositing a thermal barrier coating as in claim 18, wherein the metallic layer is comprised essentially of the following materials by percentage weight:
17.0 - 23.0 wt % Chromium 4.5 - 11.0 wt % Aluminum 0.5 - 1.20 wt % Y
0.0 - 0.20 wt % Iron Balance Nickel

45. A method of depositing a thermal barrier coating as in claim 38, wherein the metallic layer is comprised of particles having a spherical morphology.

46. A method of depositing a thermal barrier coating as in claim 38, wherein the ceramic layer is comprised of particles having a spherical morphology.