Feasibility assessment of self-grading metallic bond coat alloys for EBCs/TBCs to protect Si-Based ceramics

2005 ◽  
Vol 52 (5) ◽  
pp. 393-397 ◽  
Author(s):  
M.P. Brady ◽  
B.L. Armstrong ◽  
H.T. Lin ◽  
M.J. Lance ◽  
K.L. More ◽  
...  
Keyword(s):  
Bond Coat ◽  
Feasibility Assessment ◽  
Metallic Bond ◽  
Bond Coat Alloys

Validation of Multi-Frequency Eddy Current MWM Sensors and MWM-Arrays for Coating Production Quality and Refurbishment Assessment

2003 ◽  
Author(s):  
Vladimir Zilberstein ◽  
Ian Shay ◽  
Robert Lyons ◽  
Neil Goldfine ◽  
Thomas Malow ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Eddy Current ◽  
Coating Thickness ◽  
Bond Coat ◽  
Gas Turbines ◽  
Corrosion Damage ◽  
Operating Conditions ◽  
Ongoing Research ◽  
Metallic Bond ◽  
Thickness Measurements

Coatings for oxidation, corrosion, and thermal protection provide the required materials performance for gas turbine blades and vanes in state-of-the-art industrial gas turbines. These turbines must withstand severe operating conditions for well over ten thousand hours. Variations in the coating thickness, and increased porosity, can influence the lifetime of such coatings significantly. For components that have been removed from service, effective assessment of the aged coating and substrate condition is critical for refurbish/replace/continue-to-run decisions. A suitable device for coating thickness measurement and detection of unacceptable porosity is needed for ensuring the quality of such coatings. In this paper, we present new results on coating thickness measurements for metallic MCrAlY overlay coatings on gas turbine parts. These measurements were performed with a Meandering Winding Magnetometer (MWM®) eddy-current sensor using grid methods. This technique allows proper coating measurements even after a diffusion heat treatment for a better coating adhesive strength. The MWM technology enables measurement of the coating thickness, the absolute electrical conductivity (which may in turn be related to porosity or other properties of interest), and lift-off, which is related to surface roughness. Single-channel MWM sensors and multi-channel imaging MWM-Arrays permit capture of features of interest for a population of components. New capabilities for inspecting gas turbine components are, thus, provided. Inspection applications include metallic and non-metallic coating thickness measurements, porosity measurements, and detection of cracks on complex surfaces. Results of coating assessment for a production line of gas turbine vanes by means of a multifrequency MWM technique are presented for various combinations of coatings and base metals. A description of improved multiple frequency quantitative inversion methods is provided for simultaneous and independent measurement of multiple unknowns such as metallic bond coat thickness, metallic bond coat porosity, and top coat thickness. Ongoing research focuses on characterization of aged components using MWM sensors and imaging MWM-Arrays as well as on development of enhanced algorithms for four and five unknown coating / substrate properties. In a recent study of hot corrosion, uncoated nickel alloy specimens were characterized using an MWM sensor with grid methods. Preliminary results indicated that, within the limitations of the three-unknown single-layer model used, the method could readily identify specimens with no apparent corrosion damage, specimens with moderate corrosion damage, and specimens with severe corrosion damage.

Thermal Fatigue Damage Evaluation of EB-PVD TBC Specimens - Its Potential and Problems

2009 ◽  
Vol 631-632 ◽  
pp. 91-96
Author(s):  
Masakazu Okazaki ◽  
S. Yamagishi ◽  
Motoki Sakaguchi ◽  
T. Okamura
Keyword(s):  
Fatigue Damage ◽  
Thermal Fatigue ◽  
Bond Coat ◽  
Physical Vapor Deposition ◽  
Ring Shape ◽  
Evolution Behavior ◽  
Experimental Findings ◽  
Failure Life ◽  
Superalloy In738lc ◽  
Bond Coat Alloys

Thermal fatigue damage evolution behavior in thermal barrier coatings (TBCs) was studied, by employing the originally designed two dimensional ring-shape TBC specimen. The TBC specimen consisted of Ni-based superalloy IN738LC substrate, bond coat, and 8 wt.% Y2O3-stabilized ZrO2 (YSZ) top coat. The top coat was fabricated by electron-beam physical vapor deposition (EB-PVD) method with 250 micron-meters in thickness. Three kinds of MCrAlY bond coat alloys were specified as an experimental variable. Through the work, special attention was paid not only to the failure life of TBC specimen, but also to the underlying failure mechanisms. Some problems have been also pointed out, on feeding back these experimental findings to engineering applications.

Evaluation of Plasma Sprayed Thermal Barrier Coatings Using NDE and SEM

2007 ◽  
Author(s):  
Abbas Fahr ◽  
Catalin Mandache ◽  
Marc Genest ◽  
Weijie Chen ◽  
Xijia Wu ◽  
...  
Keyword(s):  
Thermal Barrier Coatings ◽  
Eddy Current ◽  
Thermal Imaging ◽  
Bond Coat ◽  
Elevated Temperatures ◽  
Internal Stresses ◽  
Thermal Barrier ◽  
Infrared Thermal Imaging ◽  
Barrier Coatings ◽  
Metallic Bond

Thermal barrier coatings (TBC) are used to protect the hot section components of gas turbine engines from high temperatures. A TBC system consists of a ceramic topcoat and a metallic bond coat sprayed or deposited onto the metal substrate. TBC failure is often associated with oxidation of the metallic bond coat at elevated temperatures via formation of thermally grown oxides (TGO) that cause internal stresses leading to the final spallation of the TBC. The present study explores the application of eddy current and infrared thermal imaging techniques for the detection of TGO in thermally-exposed TBC with a view of finding the damage criteria and a suitable solution for nondestructive evaluation (NDE) of TBC. The eddy current technique is based on the induction of an electromagnetic field and is sensitive to minute changes in electrical or magnetic properties of the test piece while infrared thermal imaging is based on thermal diffusion process and measures small differences in surface temperature. The NDE results are validated through destructive testing and microscopic examination of the TBC samples in as-sprayed condition and after exposure to elevated temperatures.

Mechanical property and characterization of a NiCoCrAlY type metallic bond coat used in turbine blade

2009 ◽  
Vol 505 (1-2) ◽  
pp. 96-104 ◽  
Author(s):  
Ashok Kumar Ray ◽  
Nilima Roy ◽  
Abhijit Kar ◽  
Ajoy Kumar Ray ◽  
Samir Chandra Bose ◽  
...  
Keyword(s):  
Mechanical Property ◽  
Turbine Blade ◽  
Bond Coat ◽  
Metallic Bond

The Effect of Argon Controlled Pre-Oxidation on TGO Formation of NiCoCrAlYTa/YSZ

2016 ◽  
Vol 694 ◽  
pp. 155-159
Author(s):  
I.S. Mohd Zulkifli ◽  
Muhamad Azizi Mat Yajid ◽  
Mohd Hasbullah Idris ◽  
M. Daroonparvar
Keyword(s):  
Bond Coat ◽  
Thermally Grown Oxide ◽  
Atmospheric Plasma ◽  
Inconel 625 ◽  
Thermal Barrier ◽  
High Temperature Application ◽  
Turbine Engine ◽  
Barrier Coating ◽  
Metallic Bond ◽  
Temperature Application

Thermally grown oxide (TGO) plays important roles in thermal barrier coating system (TBC) for high temperature application such as in aircraft gas turbine engine blades (GTE). The TGO formed between the bond coat and topcoat interface can increase oxidation resistance to creep of GTE blades by minimizing oxygen diffusion into the metal substrate. In this research a NiCoCrAlYTa metallic bond coat was deposited on Inconel 625 substrate using two methods of deposition namely; high velocity oxy-fuel (HVOF) and atmospheric plasma spray (APS). After coating process, both types of samples underwent pre-oxidation in argon furnace for 12-24 hours at 1000 °C. Results showed that the TGO formation for samples in which the bond coat deposited via HVOF method produced much thinner and continuous TGO formation compared to APS deposition. This TGO characteristic is very useful to lengthen the lifetime of the metals substrate.

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