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AssigneeChangchun Institute of Applied Chemistry Chinese Academy of Science
InventorsHui Dai, Jiayan Li, Xueqiang Cao, Jian Meng
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The present invention relates to a thermal barrier coating material having the chemical composition of (1−n)CeO2-nZrO2-0.5R2O3, where n is in the range of 0.9≧n≧0 and R is selected from a group consisting of Nd, Sm, Eu, Gd, Tb and combinations of at least two among them. It possesses a thermal expansion coefficient higher than 12×10−6 K−1 from ambient temperature up to 1200° C. and superior to those of the presently widely-used thermal barrier coating materials. Even if it is subjected to long time calcinations at 1400° C. or is quenched to room temperature, it can still maintain the stable crystal structure. In addition, its thermal expansion trend matches quite well with that of the bond coating alloy. This is beneficial to the elimination of thermal stress generated between the substrate and the ceramic top coating during the thermal cycle and can significantly improve the thermal shock resistance of the coating. The present invention further relates to a method for producing a thermal barrier coating material and a method for preparing a thermal barrier coating.
A thermal barrier coating material having the chemical composition of (1−n)CeO2-nZrO2-0.5R2O3, where n is in the range of 0.9≧n≧0 and R is selected from the group consisting of Nd, Sm, Eu, Gd, Tb and combinations of at least two thereof.
A thermal barrier coating material produced by a method comprising steps of:
A thermal barrier coating suitable to be used at a temperature higher than 1150° C., produced by a process comprising a step of depositing a thermal barrier coating material having the chemical composition of (1−n)CeO2-nZrO2-0.5R2O3, where n is in the range of 0.9≧n≧0 and R is selected from the group consisting of Nd, Sm, Eu, Gd, Tb and combinations of at least two thereof, on the surface of a metal substrate by means of plasma spray and/or electron beam physical vapor deposition to form a coating.
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Coating with metallic material characterised only by the composition of the metallic
Oxide or hydroxide being the only anion: containing two or more rare earth metals, e.g. NdPrO3 or LaNdPrO3
Compounds of zirconium: compounds containing zirconium, with or without oxygen or hydrogen, and containing two or more other elements
Based on oxide ceramics: based on zirconium or hafnium oxides, zirconates, zircon or hafnates
About 9 months of term left · ends 19 Jul 2027 (estimated)
This application claims the benefit of Chinese Patent Application No.: 2004100110900, filed Sep. 10, 2004.
The present invention relates to a high temperature thermal barrier coating material and a thermal barrier coating produced thereby.
Along with the developments of civilian technologies of aviation, spaceflight, thermal power and etc, the demand on higher service temperature of the hot end parts of gas turbine engine is increasing. The superalloys and their single crystals are currently used at service temperatures approaching their upper limits of thermal stability. Under such a condition, from the viewpoint of improving material, the thermal barrier coating technique has been widely used as another feasible technique of reducing the surface working temperature of the vanes of the turbine engine.
FIG. 1 shows a graph of the thermal expansion coefficient of the thermal barrier coating material of CeO2-0.5Nd2O3, the NiCrAlY bond coating material and standard 8YSZ from room temperature to 1250° C.
FIG. 2 shows a XRD spectrum of the thermal barrier coating material of CeO2-0.5Nd2O3 prepared in Example 1, obtained by using a CuKα radiation, a tube current of 20 mA and a tube voltage of 40 kV.
In the present invention, properties of high thermal stability, high corrosion resistance and low thermal conductivity are utilized to realize the protection of superalloy substrate. Therefore the choice of material for thermal barrier ceramic top coating should obey some definite principles: high melting point, no phase transition from ambient temperature to service temperature, low thermal conductivity coefficient, chemical inert, relatively higher thermal expansion coefficient, good thermal shock resistance and lower sintering ability.
CeO2 is an oxide having fluorite structure. Its thermal conductivity is smaller than that of 8YSZ and decreases exponentially with the increase of temperature while its thermal expansion coefficient is larger than that of 8YSZ and approaches that of nickel based superalloy. CeO2 as a thermal barrier coating material can raise thermal shock resistance due to the following reasons: 1) there is no transformation from tetragonal phase to monoclinic phase in the coating; 2) the coating possesses good thermal barrier property and can lower the metal substrate temperature and thus can lower the degree of oxidation of the metal substrate; and 3) the coating has higher thermal expansion coefficient. However, pure CeO2 is not suitable to be used alone due to its high oxygen diffusion rate and quick sintering ability at high temperature. In the present invention, one high temperature thermal barrier coating material with high thermal expansion coefficient, low thermal conductivity and low sintering ability is obtained by doping the CeO2 system with rare earth zirconate 0.5R2O3-nZrO2, where 0.9≧n≧0, R is selected from one group consisting of Nd, Sm, Eu, Gd, Tb and combinations of at least two among them.
The ceramic material of the present invention has the following chemical composition of (1−n)CeO2-nZrO2-0.5R2O3, where 0.9≧n≧0 and R is selected from a group consisting of Nd, Sm, Eu, Gd, Tb and combinations of at least two among them.