Effects of EB-PVD Process TGO Formation and Growth within Thermal Barrier Coatings

2007 ◽  
Vol 546-549 ◽  
pp. 1781-1788 ◽  
Author(s):  
Li Min He
Keyword(s):  
High Temperature ◽  
Oxide Layer ◽  
Thermal Barrier Coatings ◽  
Mixed Oxide ◽  
Physical Vapor Deposition ◽  
High Temperature Oxidation ◽  
Thermal Barrier ◽  
Al2o3 Layer ◽  
Temperature Oxidation ◽  
Barrier Coatings

It has been found that under oxygen partial pressure of ~2×10-6 kPa, the high-temperature oxidation of thermal barrier coatings (TBCs) occurred during an electron beam physical vapor deposition (EB-PVD) process for producing the TBCs top ceramic coating. In the present investigation, two modified bond coats (BCs) of NiCrAlY with Si addition, and NiCrAlY with Co and Hf additions, were developed by Arc Ion-plating technique to study the effects of the EB-PVD process on thermally grown oxide (TGO) formation and growth. The isothermal and cyclic oxidation tests were conducted and the cross-sectional morphologies of the specimens were examined to compare the high-temperature oxidation behaviors of the two TBCs. It was found that a mixed oxide layer have been developed in the as-deposited TBCs with a NiCrAlYSi BC. The mixed oxide layer mainly included Cr2O3, NiO, Al2O3 and their spinel. With the mixed oxide layer, TBCs with the NiCrAlYSi BC showed a superior high-temperature resistance on later high-temperature exposure to TBCs with NiCoCrAlYHf BC, where no mixed oxide layer was observed. The pre-formed mixed oxide layer apparently shortened the time to fully develop a protective α-Al2O3 layer and therefore restrained the TGO growth in TBCs.

Effect of Spray Distance on the Microstructure and High Temperature Oxidation Resistance of Plasma Spray-Physical Vapor Deposition 7YSZ Thermal Barrier Coating

2021 ◽  
Vol 1035 ◽  
pp. 511-520
Author(s):  
Wen Long Chen ◽  
Min Liu ◽  
Xiao Ling Xiao ◽  
Xin Zhang
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
Thermal Barrier Coatings ◽  
Physical Vapor Deposition ◽  
High Temperature Oxidation ◽  
Thermal Barrier ◽  
Spray Distance ◽  
Temperature Oxidation ◽  
Barrier Coatings ◽  
7Ysz Coating

In order to study the effect of spray distance on the structure and high temperature oxidation resistance of feather-columnar thermal barrier coatings, the feather-columnar ZrO2-7wt. % Y2O3 (7YSZ) thermal barrier coatings were prepared at spray distances of 650 mm, 950 mm, 1100 mm, 1250 mm, and 1400 mm by plasma spray-physical vapor deposition (PS-PVD) technology. The surface roughness, micro morphology, and porosity of the sprayed 7YSZ coating were analyzed by 3D surface profiler, SEM, XRD, etc., and the impedance spectrum characteristics of the 7YSZ coating were characterized by electrochemical alternating current (AC) impedance technology. In addition, the high temperature oxidation resistance test of 7YSZ coating under different spray distances was carried out at a temperature of 1000 °C to study the influence of spray distance on the high temperature oxidation resistance of 7YSZ coating. The research results show that the surface roughness and porosity of feather-columnar 7YSZ coating increased sequentially with the increase of spray distance. At the same time, The YSZ grain boundary resistance value increased exponentially as the porosity of the coating increases. Where the spray distance was in the range of 650 mm and 1250 mm, the high temperature oxidation rate constant of the coating increased with the spray distance. However, the spray distance was greater than 1250 mm, and the spray distance had no significant effect on the high temperature oxidation resistance of the coating.

Interfacial Kinetics of High Temperature Oxidation in YSZ Thermal Barrier Coatings With Bond Coatings of NiCoCrAlY With 0.25% Hf

2009 ◽  
Author(s):  
Winston Soboyejo ◽  
Patrick Mensah ◽  
Ravinder Diwan
Keyword(s):  
High Temperature ◽  
Thermal Barrier Coatings ◽  
High Temperature Oxidation ◽  
Structural Evolution ◽  
Isothermal Oxidation ◽  
Thermally Grown Oxide ◽  
Thermal Barrier ◽  
Temperature Oxidation ◽  
Barrier Coatings ◽  
Thermally Grown

This paper presents the results of an experimental study of the high-temperature isothermal oxidation behavior and micro-structural evolution in plasma sprayed thermal barrier coatings (TBCs) at temperatures between 900 and 1200 °C. Two types of specimens were produced for testing. These include a standard and vertically cracked (VC) APS. High temperature oxidation has been carried out at 900, 1000, 1100 and 1200 °C. The experiments have been performed in air under isothermal conditions. At each temperature, the specimens are exposed for 25, 50, 75 and 100 hours. The corresponding microstructures and microchemistries of the TBC layers are then examined using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy EDS. Changes in the dimensions of the thermally grown oxide (TGO) layer are determined as functions of time and temperature. The evolution of bond coat microstructures/interdiffusion zones and thermally grown oxide (TGO) layers are compared in TBCs with standard (STD) and vertically cracked (VC) microstructures.

The Effect of Laser Glazing on High Temperature Oxidation Resistance of Thermal Barrier Coatings

2012 ◽  
Vol 433-440 ◽  
pp. 315-318
Author(s):  
Seyid Fehmi Diltemiz ◽  
Melih Cemal Kushan
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
High Temperature Oxidation ◽  
304 Stainless Steel ◽  
Thermal Barrier ◽  
Laser Glazing ◽  
Temperature Oxidation ◽  
Barrier Coatings

Thermal barrier coatings (TBCs) have been widely used by aero and land based gas turbines to protect hot section parts from oxidation and thermal loads. These coatings are generally consisting of multiple layers of coating (usually two) with each layer having a specific function. TBCs are generally deposited with air plasma spray (APS) or electron beam physical vapor deposition (EB-PVD) techniques. In this paper plasma sprayed TBCs were deposited on to 304 stainless steel substrates then ceramic surfaces were glazing with Nd-YAG laser. Metallographic examinations were applied to the samples to investigate microstructural changes in glazed ceramic layer. Both glazed and as-coated samples were subjected to oxidation tests to measure the high temperature oxidation resistance. The tests showed that, laser glazing is beneficial to oxidation resistance of TBCs. This improvement is attributed to sintering of zirconia layer which act as oxygen barrier and formed during glazing process.

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