Compositional Factors Affecting the Oxidation Behavior of Pt-Modified γ-Ni+γ’-Ni3Al-Based Alloys and Coatings

2008 ◽  
Vol 595-598 ◽  
pp. 239-247 ◽  
Author(s):  
N. Mu ◽  
Takeshi Izumi ◽  
L. Zhang ◽  
Brian Gleeson
Keyword(s):  
High Temperature ◽  
Gas Turbines ◽  
Cyclic Oxidation ◽  
Oxidation Behavior ◽  
Thermally Grown Oxide ◽  
Factors Affecting ◽  
Barrier Coating ◽  
Α Al2o3 ◽  
Slow Growing ◽  
Tbc Systems

Many high-temperature coatings rely on the formation of a continuous and adherent thermally grown oxide (TGO) scale of α-Al2O3 for extended resistance to degradation. For instance, the durability and reliability of thermal barrier coating (TBC) systems in gas turbines are critically linked to the oxidation behavior and stability of an alumina-forming β-NiAl-based bond coat. This study focuses primarily on the development of unique Pt+Hf-modified γ′-Ni3Al+γ-Ni coating compositions that form highly adherent, slow-growing TGO scales during both isothermal and cyclic oxidation at high temperature. Recent findings on the isothermal and cyclic oxidation behavior of γ′+γ alloys and coatings will be discussed, with particular emphasis on the effects of Pt, Al and Hf contents and distributions. Inferred reasons for the observed “Pt effect” will also be presented.

Formation of Pt-Modified γ’-Ni3Al and Re-Based σ-Alloy Coating System and Cyclic Oxidation Behavior of Coated Superalloy

2008 ◽  
Vol 595-598 ◽  
pp. 135-141 ◽  
Author(s):  
Toshio Narita ◽  
Stewart Ford ◽  
Takayuki Yoshioka ◽  
Takumi Nishimoto ◽  
Takeshi Izumi ◽  
...  
Keyword(s):  
Single Crystal ◽  
Cyclic Oxidation ◽  
Oxidation Behavior ◽  
Parabolic Rate Constant ◽  
Alloy Coating ◽  
Coating System ◽  
Barrier Coating ◽  
Coated Alloy ◽  
Α Al2o3 ◽  
Slow Growing

A duplex layer, outer Pt-modified γ’-Ni3Al + γ-Ni and inner multi-barrier σ- Re(Cr,Ni,W), coating system was formed on a Ni-based single crystal 4th generation superalloy. Oxidation behavior of the coated alloy was investigated under thermo-cycling conditions, and analyzed by EPMA and XRD. During cyclic oxidation 1hr at 1100°C and 20 min at room temperature, a slow growing α-Al2O3 formed for up to 400 cycles and its spallation was rare. The parabolic rate constant of mass change was 6.3x10-16 kg2m-4s-1. The Pt-modified γ’-Ni3Al + γ-Ni contained 19Al, 12Pt, 4Cr, and 3Co in at%, and their concentration profiles were almost flat across the outer layer. The multi-barrier, σ-Re(Cr,Ni,W) contained 40Re, 23Cr, 17Ni, 7Al, 4W, 3.5Mo, and 3Co in at%. Furthermore, the γ’-Ni3Al containing Pt was newly formed between the multibarrier and bulk alloy substrate. It was concluded that the σ-Re(Cr,Ni,W) is compatible with the Ptmodified γ’-Ni3Al in the multi-diffusion barrier coating on Ni-based single crystal, 4th generation superalloy at high temperatures.

R&D Status and Needs for Improved EB-PVD Thermal Barrier Coating Performance

2000 ◽  
Vol 645 ◽  
Author(s):  
C. Leyens ◽  
U. Schulz ◽  
M. Bartsch ◽  
M. Peters
Keyword(s):  
Thermal Barrier Coating ◽  
Bond Coat ◽  
Gas Turbines ◽  
Systems Approach ◽  
Thermally Grown Oxide ◽  
Thermal Barrier ◽  
Factors Affecting ◽  
Performance Improvements ◽  
Barrier Coating ◽  
Temperature Capability

ABSTRACTThe key issues for thermal barrier coating development are high temperature capability and durability under thermal cyclic conditions as experienced in the hot section of gas turbines. Due to the complexity of the system and the interaction of the constituents, performance improvements require a systems approach. However, there are issues closely related to the ceramic top coating and the bond coat, respectively. Reduced thermal conductivity, sintering, and stresses within the ceramic coating are addressed in the paper as well as factors affecting failure of the TBC by spallation. The latter is primarily governed by the formation and growth of the thermally grown oxide scale and therefore related to the bond coat. A strategy for lifetime assessment of TBCs is discussed.

A Brief Overview on High Temperature Friction and Wear

2010 ◽  
Author(s):  
Mustafa Bulut Coskun ◽  
Mahmut Faruk Aksit
Keyword(s):  
High Temperature ◽  
Gas Turbines ◽  
Friction And Wear ◽  
Oxidation Behavior ◽  
Elevated Temperatures ◽  
Wear Performance ◽  
Large Pressure ◽  
Higher Power ◽  
Vibratory Motion ◽  
Increasing Temperature

With the race for higher power and efficiency new gas turbines operate at ever increasing pressures and temperatures. Increased compression ratios and firing temperatures require many engine parts to survive extended service hours under large pressure loads and thermal distortions while sustaining relative vibratory motion. On the other hand, wear at elevated temperatures limits part life. Combined with rapid oxidation for most materials wear resistance reduces rapidly with increasing temperature. In order to achieve improved wear performance at elevated temperatures better understanding of combined wear and oxidation behavior of high temperature super alloys and coatings needed. In an attempt to aid designers for high temperature applications, this work provides a quick reference for the high temperature friction and wear research available in open literature. High temperature friction and wear data have been collected, grouped and summarized in tables.

scholarly journals Development of Evaluation Method for Damage of Oxidation CoNiCrAlY Coating

2019 ◽  
Vol 804 ◽  
pp. 47-51
Author(s):  
Mo Chen ◽  
Kodai Yoshikawa ◽  
Zhen Qiang Song ◽  
Shijie Zhu
Keyword(s):  
Cross Sections ◽  
Gas Turbines ◽  
Evaluation Method ◽  
Thermal Spraying ◽  
Optical Microscope ◽  
Thermally Grown Oxide ◽  
Interfacial Damage ◽  
Barrier Coating ◽  
Plasma Sprayed ◽  
Conicraly Coating

The bond coat plays an important role in the failure of the thermal barrier coating (TBC) system used for gas turbines [1,2]. In this research, the CoNiCrAlY coated Ni-base superalloy specimens were used for developing evaluation method for interfacial damage in the coat. Samples were exposed at 1000°C and 1100°C for up to 1000 hours. The morphology and residual stress in the thermally grown oxide (TGO) layer on the CoNiCrAlY coating were characterized by microscopic observation and luminescence spectroscope, respectively. The microstructure and damage o\n both the coating surfaces and the cross sections were observed by optical microscope and scanning electron microscope. According to the results, the low pressure plasma sprayed CoNiCrAlY coating (LPPS) showed the thinnest TGO layer and lowest residual stress.Residual stress decreased with an increase in exposure time, depending on the morphology of TGO layer. The effects of thermal spraying methods on the oxidation of yttrium in TGO layer and BC layer and its influence on interfacial damage were discussed.

High temperature cyclic oxidation behavior of a low manganese Fe12Mn9Cr5Si4Ni-NbC shape memory stainless steels

2021 ◽  
Vol 857 ◽  
pp. 158198
Author(s):  
Artur Mariano de Sousa Malafaia ◽  
Rodrigo da Silva ◽  
Carlos Alberto Della Rovere ◽  
Renato Baldan ◽  
Lucía Suárez-Fernández ◽  
...  
Keyword(s):  
High Temperature ◽  
Shape Memory ◽  
Stainless Steels ◽  
Cyclic Oxidation ◽  
Oxidation Behavior

Interfacial Fracture Analysis in EB-PVD/PTAL TBC Systems

2009 ◽  
Author(s):  
Q. Ma ◽  
J. L. Beuth ◽  
G. H. Meier ◽  
F. S. Pettit
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Gas Turbines ◽  
Physical Vapor Deposition ◽  
Heat Insulation ◽  
Thermally Grown Oxide ◽  
Aircraft Engines ◽  
Tbc Systems ◽  
Rate Formulation

Thermal barrier coatings (TBCs) have been utilized for more than four decades to increase the efficiency and durability of aircraft engines as well as land based gas turbines. Though the function of the thin TBC layer is heat insulation, it is critically important for it to maintain adherence in service. In this paper, we address some fundamental aspects of TBC debonding failure in electron beam physical vapor deposition (EB-PVD) TBC systems that had been considered in a previous study. We demonstrate that the energy release rate formulation for EB-PVD TBC systems based on as-processed conditions and a thin thermally grown oxide (TGO) layer overestimates the energy release rate for exposed TBC systems having thicker TGO layers. A modified formulation is given, applicable to exposed TBC systems. A finite element contact and fracture model is used to validate the formulation as well as study crack mode mixity. Mode II interfacial cracking is shown to be dominant for practical TGO thicknesses seen in exposed EB-PVD TBC systems.

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