Substrate Effect on the Lifetime of EB-PVD TBC Systems With 7YSZ and GDZ as Ceramic Top Coat Materials

2014 ◽  
Author(s):  
Ahmed Umar Munawar ◽  
Uwe Schulz ◽  
Giovanni Cerri ◽  
Hendrik Lau
Keyword(s):  
High Temperature ◽  
Physical Vapor Deposition ◽  
Substrate Material ◽  
Layered System ◽  
High Temperature Strength ◽  
Air Cooling ◽  
Temperature Capability ◽  
Forced Air ◽  
Tbc Lifetime ◽  
Tbc Systems

Thermal barrier coatings (TBCs) consist of a multi-layered system where the different layers are deposited to improve the high temperature capability of the underlying substrate material. Substrate materials are usually made of Ni-based superalloys which have an outstanding combination of high-temperature strength, toughness and resistance to degradation in corrosive or oxidizing environments. In this study, the effect of different substrate materials on cyclic TBC lifetime has been studied by using two different superalloys, IN100 and CMSX-4, as the substrate materials. Two different ceramic topcoat materials, 7wt. % yttria partially stabilized zirconia (7YSZ) and Gadolinium Zirconate (GdZ), have been deposited on NiCoCrAlY bond coats. All depositions in this study have been carried out by Electron Beam Physical Vapor Deposition (EB-PVD). Lifetime measurements have been done by holding the systems at 1100°C for 50mins and then reducing the temperature to ambient level by forced air cooling for 10mins. The TBC lifetime in case of IN100 substrates is higher than on CMSX-4. The use of GdZ as topcoat material improves the lifetime for both IN100 and CMSX-4 based TBC systems, however, the lifetime for CMSX-4 based TBC system is still shorter than its IN100 counterpart. In this study, lifetime comparisons, changes in the microstructure and diffusion of different elements in the system are investigated.

Fibrous composites with high melting-point matrices

1970 ◽  
Vol 319 (1536) ◽  
pp. 33-44 ◽  
Keyword(s):  
High Temperature ◽  
Epoxy Resins ◽  
Base Alloy ◽  
High Temperature Strength ◽  
High Melting Point ◽  
Temperature Capability ◽  
Strength And Stiffness ◽  
Nickel Base ◽  
Fibre Matrix ◽  
Selection Of

It is now well established that the strength and stiffness of materials such as epoxy resins and aluminium can be increased by the incorporation of suitable fibres. However, relatively little effort has been made to improve similarly the high temperature strength of materials intended for service above ca . 800°C. This paper is introduced with a general examination of fibre/matrix systems that offer improved high temperature capability over current materials, with reference to gas turbine blade applications. The importance of properties and characteristics that influence the selection of suitable fibre and matrix combinations, for example, density, strength, oxidation resistance and compatibility, are discussed. Experi­mental work on the strength of potentially useful fibres such as refractory metal and alumina filaments, their incorporation into nickel-base alloy matrices using vacuum-casting techniques, and the evaluation of composites are described. In terms of the measured properties and of strength predictions based on fibre and matrix data, the merits and limitations of composites relative to well-developed alloys strengthened by precipitation mechanisms are considered.

scholarly journals Capturing the Competing Influence of Thermal and Mechanical Loads on the Strain of Turbine Blade Coatings via High Energy X-rays

Coatings ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 320 ◽  
Author(s):  
Albert Manero ◽  
Kevin Knipe ◽  
Janine Wischek ◽  
Carla Meid ◽  
John Okasinski ◽  
...  
Keyword(s):  
High Temperature ◽  
Physical Vapor Deposition ◽  
Mechanical Load ◽  
High Energy ◽  
Thermally Grown Oxide ◽  
Air Cooling ◽  
Internal Cooling ◽  
X Rays ◽  
Design Strategies ◽  
Barrier Coating

This paper presents findings of synchrotron diffraction measurements on tubular specimens with a thermal barrier coating (TBC) system applied by electron beam physical vapor deposition (EB-PVD), having a thermally grown oxide (TGO) layer due to aging in hot air. The diffraction measurements were in situ while applying a thermal cycle with high temperature holds at 1000 °C and varying internal air cooling mass flow and mechanical load. It was observed that, during high temperature holds at 1000 °C, the TGO strain approached zero if no mechanical load or internal cooling was applied. When applying a mechanical load, the TGO in-plane strain (e22) changed to tensile and the out of plane TGO strain (e11) became compressive. The addition of internal cooling induced a thermal gradient, yielding a competing effect, driving the e22 strain to compressive and e11 strain to tensile. Quantifying TGO strain variations in response to competing factors will provide a path to controlling the TGO strain, and further improving the lifetime assessment and durability design strategies for TBC systems.

Microstructural Evolution of GdZ and DySZ Based EB-PVD TBC Systems After Thermal Cycling at High Temperature

2013 ◽  
Author(s):  
Ahmed Umar Munawar ◽  
Uwe Schulz
Keyword(s):  
High Temperature ◽  
Thermal Cycling ◽  
Physical Vapor Deposition ◽  
Temperature Stability ◽  
Life Time ◽  
Double Layers ◽  
Inlet Temperature ◽  
High Temperature Stability ◽  
Turbine Inlet Temperature ◽  
Tbc Systems

Lower thermal conductivity and high temperature stability are the two properties which are highly desired from ceramic top coat materials in TBC systems. Gadolinium Zirconate, Gd2Zr2O7, (GdZ) and Dyprosia Stabilized Zirconia (DySZ) are two of the candidate materials with such properties and consequently the TBC system would be able to work at higher turbine inlet temperature (TIT) or the lifetime can be increased. In the present study, life time measurements are done for single and double layered Electron Beam Physical Vapor Deposition (EB-PVD) GdZ and DySZ samples by thermal-cycling tests. The double layered TBCs consisted of a thin 7YSZ layer and, on top, the new candidate material. Both single and double layered samples of GdZ and DySZ have shown similar or better lifetimes than the standard 7YSZ samples. However, single layered TBCs showed better lifetime results than the respective double layers. In this study, changes in the microstructure, diffusion of elements and sintering of the TBC materials with aging are observed.

Microstructural Evolution of GdZ and DySZ Based EB-PVD TBC Systems After Thermal Cycling at High Temperature

2013 ◽  
Vol 135 (10) ◽  
Author(s):  
Ahmed Umar Munawar ◽  
Uwe Schulz ◽  
Giovanni Cerri
Keyword(s):  
High Temperature ◽  
Thermal Cycling ◽  
Physical Vapor Deposition ◽  
Temperature Stability ◽  
Double Layers ◽  
Inlet Temperature ◽  
High Temperature Stability ◽  
Turbine Inlet Temperature ◽  
Barrier Coating ◽  
Tbc Systems

Lower thermal conductivity and high temperature stability are the two properties which are highly desired from ceramic top coat materials in thermal barrier coating (TBC) systems. Gadolinium zirconate, Gd2Zr2O7 (GdZ) and dyprosia stabilized zirconia (DySZ) are two of the candidate materials with such properties and consequently the TBC system would be able to work at higher turbine inlet temperature (TIT) or the lifetime can be increased. In the present study, lifetime measurements are done for single and double layered electron beam physical vapor deposition (EB-PVD) GdZ and DySZ samples by thermal-cycling tests. The double layered TBCs consisted of a thin 7YSZ layer and, on top, the new candidate material. Both single and double layered samples of GdZ and DySZ have shown similar or better lifetimes than the standard 7YSZ samples. However, single layered TBCs showed better lifetime results than the respective double layers. In this study, changes in the microstructure, diffusion of elements and sintering of the TBC materials with aging are observed.

Influence of Thermo-Mechanical Processing on the Microstructure of Beryllia Dispersed Nickel Alloys

1973 ◽  
Vol 31 ◽  
pp. 184-185
Author(s):  
M.S. Grewal ◽  
S.A. Sastri ◽  
N.J. Grant
Keyword(s):  
High Temperature ◽  
Nickel Alloys ◽  
Thermomechanical Processing ◽  
Cold Work ◽  
High Temperature Strength ◽  
Strengthening Effect ◽  
Mechanical Processing ◽  
Uniform Dispersion ◽  
Oxide Particles ◽  
Nickel Base

Currently there is a great interest in developing nickel base alloys with fine and uniform dispersion of stable oxide particles, for high temperature applications. It is well known that the high temperature strength and stability of an oxide dispersed alloy can be greatly improved by appropriate thermomechanical processing, but the mechanism of this strengthening effect is not well understood. This investigation was undertaken to study the dislocation substructures formed in beryllia dispersed nickel alloys as a function of cold work both with and without intermediate anneals. Two alloys, one Ni-lv/oBeo and other Ni-4.5Mo-30Co-2v/oBeo were investigated. The influence of the substructures produced by Thermo-Mechanical Processing (TMP) on the high temperature creep properties of these alloys was also evaluated.

Application of TEM to Deformation, Wear, and Fracture of Ceramics

1974 ◽  
Vol 32 ◽  
pp. 472-473
Author(s):  
B. J. Hockey
Keyword(s):  
Wear Resistance ◽  
High Temperature ◽  
Mechanical Behavior ◽  
Brittle Materials ◽  
High Temperature Strength ◽  
Wide Range ◽  
Corrosive Environments ◽  
Further Development

Ceramics, such as Al2O3 and SiC have numerous current and potential uses in applications where high temperature strength, hardness, and wear resistance are required often in corrosive environments. These materials are, however, highly anisotropic and brittle, so that their mechanical behavior is often unpredictable. The further development of these materials will require a better understanding of the basic mechanisms controlling deformation, wear, and fracture.The purpose of this talk is to describe applications of TEM to the study of the deformation, wear, and fracture of Al2O3. Similar studies are currently being conducted on SiC and the techniques involved should be applicable to a wide range of hard, brittle materials.

Lattice Imaging of Grain Boundaries in Ceramics

1977 ◽  
Vol 35 ◽  
pp. 114-115
Author(s):  
D. R. Clarke ◽  
G. Thomas
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Grain Boundaries ◽  
High Temperature Strength ◽  
Current Interest ◽  
Lattice Imaging ◽  
Special Significance ◽  
Structural Applications ◽  
Refractory Ceramics

Grain boundaries have long held a special significance to ceramicists. In part, this has been because it has been impossible until now to actually observe the boundaries themselves. Just as important, however, is the fact that the grain boundaries and their environs have a determing influence on both the mechanisms by which powder compaction occurs during fabrication, and on the overall mechanical properties of the material. One area where the grain boundary plays a particularly important role is in the high temperature strength of hot-pressed ceramics. This is a subject of current interest as extensive efforts are being made to develop ceramics, such as silicon nitride alloys, for high temperature structural applications. In this presentation we describe how the techniques of lattice fringe imaging have made it possible to study the grain boundaries in a number of refractory ceramics, and illustrate some of the findings.

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