Microstructural features of mechanical failure behavior for plasma sprayed thermal barrier coating systems at ambient and elevated temperatures

2004 ◽  
Vol 2004.9 (0) ◽  
pp. 117-118
Author(s):  
Satoru TAKAHASHI ◽  
Masayuki YOSHIBA ◽  
Yoshio HARADA
Keyword(s):  
Thermal Barrier Coating ◽  
Elevated Temperatures ◽  
Mechanical Failure ◽  
Failure Behavior ◽  
Thermal Barrier ◽  
Barrier Coating ◽  
Plasma Sprayed

In Situ Observation of Failure Behavior for Plasma Sprayed Thermal Barrier Coating Systems under Static Loadings

2006 ◽  
Vol 522-523 ◽  
pp. 345-352 ◽  
Author(s):  
Satoru Takahashi ◽  
Masayuki Yoshiba ◽  
Raito Kawamura ◽  
Yoshio Harada
Keyword(s):  
Thermal Barrier Coating ◽  
Elevated Temperatures ◽  
Testing Temperature ◽  
Fundamental Aspect ◽  
Failure Behavior ◽  
Thermal Barrier ◽  
In Situ Observation ◽  
Barrier Coating ◽  
Plasma Sprayed

In situ observation of the mechanical failure behavior was conducted for different kinds of the plasma sprayed thermal barrier coating (TBC) systems by means of an optical microscopy under the static loadings at room and elevated temperatures; as the fundamental aspect, in order to clarify the thermomechanical failure mechanism of TBC system in connection with various coating characteristics. Mechanical tensile or compressive loading was applied progressively to the TBC specimen by an axial loading mode. It was found that the failure behavior of TBC system depends strongly on the testing temperature under both the tensile and compressive loadings. At the elevated temperature which is higher than the ductile-brittle transition temperature (DBTT) of metallic bond-coat (BC), in particular, the ceramic top-coat (TC) spallation can be prevented by virtue of the stress relief induced by the enhanced plastic flow in the BC layer. At the room temperature which is lower than the DBTT of BC, on the contrary, the TC spalling was inevitably induced, but the initiation site of TC spalling is closely related with the magnitude of local plastic deformation in the alloy substrate. Furthermore, an influence of thermally grown oxides (TGO) layer developed at the TC / BC interface on the crack initiation and propagation behavior was investigated in some detail.

The Effect of Tungsten Contamination from the Spray Gun on the Performance of a Thermal Barrier Coating

1997 ◽  
Author(s):  
J. Wigren ◽  
L. Pejryd ◽  
H. Karlsson
Keyword(s):  
Thermal Barrier Coating ◽  
Elevated Temperatures ◽  
Thermal Barrier ◽  
Barrier Coating ◽  
And Performance ◽  
Sprayed Coating ◽  
In The Beginning ◽  
Plasma Sprayed ◽  
Plasma Spray Gun ◽  
Spray Gun

Abstract A traditional plasma spray gun consists of an anode and a cathode. During spraying small particles of anode material of either copper or tungsten, depending on the brand of the gun, will be worn off and deposited in the coating. The size and frequency of the particles from a copper anode has generally a dramatic appearance (in the beginning or at the end of its life) whereas a tungsten nozzle normally behaves more randomly during its life. Tungsten particles can therefore be expected anywhere in a plasma sprayed coating. Unfortunately the material properties of tungsten is not very compatible with a thermal barrier coating of partially stabilized zirconia and it is shown that a contamination will cause a catastrophic failure, if located in, for a thermal barrier, a critical region. The behavior of tungsten at elevated temperatures is investigated and clearly show the detrimental effect of tungsten on the life and performance of a thermal barrier coating.

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