Thermal barrier coating with thermoluminescent indicator material embedded therein
A coating material ( 20 ) for coating a machine component ( 10 ), especially a gas turbine or a part thereof, comprises a mixture of at least a refractory material and an indicator material having an optical emission (e.g. fluorescence) spectrum which varies in response to a physical parameter of the coated component. In a preferred embodiment, the coating consists of yttrium aluminum garnet (YAG) or yttrium stabilized zirconium. The dopant is preferably a rare earth metal, e.g. Eu, Tb, Dy.
1. A thermal barrier coating on a machine component, the coating comprising a mixture of at least a refractory material and an indicator material having an optical emission spectrum which varies in response to a change in a physical parameter of the component, thereby enabling assessment or measurement of the change in the physical parameter by analysis of light collected from the component.
2. A machine having one or more internal components coated with the coating according to claim 1 , wherein the machine comprises:
a light source for directing an interrogating light beam onto the one or more components;
a light collector for collecting light from the one or more components; and
an analyser for detecting the change in the physical parameter by analysis of light collected from the one or more components, such as to provide for assessment or measurement of the change in the physical parameter.
3. The machine according to claim 2 , wherein the one or more components is coated with one or more priming layers over which the coating is further coated.
4. The machine according to claim 2 , wherein the indicator material has an optical emission spectrum which varies in response to a change in at least one other physical parameter of the respective component, and the analyser is configured to detect the change in the at least one other physical parameter of the one or more components by analysis of light collected from the one or more components.
5. The machine according to claim 2 , wherein the indicator material has an optical emission spectrum which varies in response to at least one physical parameter selected from the group consisting of a temperature of at least a region of the one or more components, a physical strain applied to at least a region of the one or more components, erosion of at least a region of the one or more components, and a physical stress of at least a region of the one or more components.
6. The machine according to claim 2 , wherein the refractory material is selected from the group consisting of yttria stabilised zirconia, yttria partially stabilised zirconia, and yttria aluminum garnet.
7. The machine according to claim 2 , wherein the indicator material is a phosphor material or a rare earth dopant, preferably selected from the group consisting of terbium, europium, and dysprosium.
8. The machine according to claim 2 , wherein the indicator material comprises a compositionally-graded material, a composite material, or a multi-phase material.
9. The machine according to claim 2 , wherein the coating comprises a layered structure, wherein (i) each of the layers includes an indicator material having different respective emission spectra, or (ii) the layered structure comprises an outermost, substantially transparent region and a region including an indicator material optically interogatable through the substantially transparent region.
10. The machine according to claim 2 , wherein the machine is a combustion engine, preferably a gas turbine engine, and more preferably a turbine blade or a heat shield.
11. The machine according to claim 2 , wherein the coating has sufficient thickness and thermal and structural properties as to form an effective barrier between the one or more components and an extreme environment such as an interior of a gas turbine engine.
12. The machine according to claim 2 , wherein the coating is a multi-phase structure in which the refractory material comprises yttria stabilized zirconia and the indicator material comprises rare earth doped yttria aluminium garnet.
13. A method of detecting a change in a physical parameter of one or more components of a machine, comprising the steps of:
providing a machine having one or more internal components coated with a thermal barrier coating comprising a mixture of at least a refractory material and an indicator material having an optical emission spectrum which varies in response to the change in the physical parameter;
directing an interrogating light beam onto the one or more components;
collecting light from the one or more components; and
detecting a change in the physical parameter of the one or more components by analysis of light collected from the one or more components, such as to provide for assessment or measurement of the change in the physical parameter.
14. The method according to claim 13 , wherein the one or more components are coated with one or more priming layers over which the coating is further coated.
15. The method according to claim 13 , wherein the indicator material has an optical emission spectrum which varies in response to a change in at least one other physical parameter of the one or more components.
16. The method according to claim 13 , wherein the indicator material has an optical emission spectrum which varies in response to at least one physical parameter selected from the group consisting of a temperature of at least a region of the one or more components, a physical strain applied to at least a region of the one or more components, erosion of at least a region of the one or more components, and a physical stress of at least a region of the one or more components.
17. The method according to claim 13 , wherein the refractory material is selected from the group consisting of yttria stabilised zirconia, yttria partially stabilised zirconia, and yttria aluminium garnet.
18. The method according to claim 13 , wherein the indicator material is a phosphor material or a rare earth dopant, preferably selected from the group consisting of terbium, europium, and dysprosium.
19. The method according to claim 13 , wherein the indicator material comprises a compositionally-graded material, a composite material, or a multi-phase material.
20. The method according to claim 13 , wherein the coating comprises a layered structure, wherein (i) each of the layers includes an indicator material having different respective emission spectra, or (ii) the layered structure comprises an outermost, substantially transparent region and a region including an indicator material optically interogatable through the substantially transparent region.
21. The method according to claim 13 , wherein the one or more components are components of a combustion engine, preferably a gas turbine, and more preferably a turbine blade or a heat shield.
22. The method according to claim 13 , where the coating has sufficient thickness and thermal and structural properties as to form an effective barrier between the one or more components and an extreme environment such as an interior of a gas turbine engine.
23. The method according to claim 13 , wherein the coating is a multi-phase structure in which the refractory material comprises yttria stabilized zirconia and the indicator material comprises rare earth doped yttria aluminium garnet.