Evaluation of Hot Corrosion Resistance of Directionally Solidified Nickel-Based Superalloy

2015 ◽  
Vol 227 ◽  
pp. 337-340 ◽  
Author(s):  
Maria Sozańska ◽  
Barbara Kościelniak ◽  
Lucjan Swadźba
Keyword(s):  
Corrosion Resistance ◽  
Chemical Composition ◽  
Hot Corrosion ◽  
Turbine Blades ◽  
Nickel Superalloy ◽  
Material Surface ◽  
Scale Morphology ◽  
Directionally Solidified ◽  
Nickel Based Superalloy ◽  
Two Temperatures

The turbine blades made of directionally solidified nickel-based superalloys are exposed to combination of high temperature and aircraft environment, in which appear corrosive elements like sulphur, sodium and vanadium (hot corrosion). Corrosion resistance of superalloys is mainly dependent on their structure and chemical composition. Therefore, it is important to be aware of the correlation between the hot corrosion and changes in chemical composition and morphology of a surface of the material. The following paper presents the influence of sulphur on the microstructure of directionally solidified nickel-based superalloy. The research was carried out in Na2SO4 environment at two temperatures of 850oC and 900oC (below and above the melting point of salt, 884°C). The results show scale morphology on material surface and changes in chemical composition of surface of nickel superalloy.

scholarly journals THE DEVELOPMENT OF THE NEW VZhM200 SUPERALLOY AND THE TECHNOLOGY OF ITS PRODUCTION FOR CASTING OF THE ADVANCED ENGINES’ BLADES BY THE DIRECTIONAL CRYSTALLIZATION

2021 ◽  
pp. 11-18
Author(s):  
P.G. Min ◽  
◽  
V.E. Vadeev ◽  
V.V. Kramer ◽  
◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Chemical Composition ◽  
Turbine Blades ◽  
Manufacturing Technology ◽  
Type Structure ◽  
Turbine Engines ◽  
Directional Crystallization ◽  
Metal Impurities ◽  
Nickel Based Superalloy

FSUE «VIAM» has developed a new nickel-based superalloy VZhM200 and its manufacturing technology for casting of turbine blades with directional (pillar-type) structure for advanced turbine engines. The advantages of the VZhM200 alloy over the DS200 Hf alloy are presented in the article. The quality of VZhM200 alloy produced by FSUE «VIAM» meets the DS200 Hf, MAR M200+Hf alloys produced by Cannon-Muskegon Corporation and HOWMET Ltd in chemical composition, content of harmful and non-metal impurities, gases and mechanical properties.

scholarly journals Effects of Different Surface Native Pre-Oxides on the Hot Corrosion Properties of Nickel-Based Single Crystal Superalloys

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5774
Author(s):  
Zehao Chen ◽  
Shusuo Li ◽  
Mengmeng Wu ◽  
Yanling Pei ◽  
Shengkai Gong ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Single Crystal ◽  
Hot Corrosion ◽  
Corrosion Properties ◽  
Al2o3 Layer ◽  
Nickel Based Superalloy ◽  
Surface Oxides ◽  
The Relationship ◽  
Positive Effect

A study is carried out on the effect of different surface native pre-oxides on hot corrosion of single crystal nickel-based superalloy at 900 °C. The effect of different oxides formed by different superalloys through pre-oxidation on hot corrosion is verified by normal hot corrosion and tube sealing experiments. The relationship between different surface oxides and the effect of different surface oxides layer on the hot corrosion properties of alloys are studied. In summary, the stable and dense surface pre-Al2O3 layer which can be obtained by pre-oxidation has an obvious positive effect on the improvement of superalloy hot corrosion resistance in reaction. In addition, the internal sulfides are analyzed in depth, and the relationship between Cr, Mo, O and S is discussed in detail.

Identification and Evaluation of Freckles in Directionally Solidified Casting Made of PWA 1426 Nickel-Based Superalloy

2012 ◽  
Vol 57 (2) ◽  
pp. 559-564 ◽  
Author(s):  
B. Chmiela ◽  
M. Sozańska ◽  
J. Cwajna
Keyword(s):  
Mechanical Properties ◽  
Electron Backscatter Diffraction ◽  
Turbine Blades ◽  
Casting Defects ◽  
Directionally Solidified ◽  
Nickel Based Superalloy ◽  
Aero Engine ◽  
And Performance ◽  
Backscatter Diffraction ◽  
Equiaxed Grains

Identification and Evaluation of Freckles in Directionally Solidified Casting Made of PWA 1426 Nickel-Based SuperalloyManufacturing of modern aero engine turbine blades made of nickel-based superalloys is very complex and expensive. The thrust and performance of new engines must address constantly more demanding requirements. Therefore, turbine blades must be characterised by very good mechanical properties, which is possible only if the blades are free of casting defects. An important innovation has been the launching of directionally solidified (DS) and single crystal (SX) turbine blades. But, manufacturing procedures and the chemical composition of many superalloys promote the formation of casting defects that are characteristic only for directional solidification. One of these defects is freckles. Freckles are small equiaxed grains in the form of long chains parallel to the solidification direction and are located on the surface of the casting. Freckles decrease the mechanical properties of DS and SX blades; therefore, they should be always unambiguously identified to improve the manufacturing process. This work presents the possibilities of identifying and evaluating freckles in DS casting made of PWA 1426 superalloy by combining the scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and electron backscatter diffraction (EBSD) techniques.

The Influence of Turbine Blade Geometry and Process Parameters on the Structure of Zr Modified Aluminide Coatings Deposited by CVD Method on the ZS6K Nickel Superalloy

2013 ◽  
Vol 197 ◽  
pp. 58-63
Author(s):  
Marek Góral ◽  
Maciej Pytel ◽  
Ryszard Filip ◽  
Jan Sieniawski
Keyword(s):  
Chemical Composition ◽  
Turbine Blade ◽  
Process Parameters ◽  
Aluminide Coating ◽  
Turbine Blades ◽  
Leading Edge ◽  
Nickel Superalloy ◽  
Influence Of Process Parameters ◽  
Aluminide Coatings ◽  
Blade Geometry

The Zr modified aluminide coatings is an alternative concept for replacing Pt-modified aluminide bondcoat for thermal barrier coatings. In the paper the influence of process parameters on the chemical composition and the thickness of aluminide coatings will be presented. The zirconia-doped aluminide coating was deposited on turbine blades made from ZS6K nickel superalloy during the low-activity CVD process. In recent work the influence of turbine blade geometry on thickness of coating was observed. The thickest coating was observed on the trailing and leading edge on the blade cross-section. In the conducted research, the light and scanning electron microscopy were used as well as the EDS chemical composition microanalysis.

Degradation of Diffusive Aluminide Coating after Service in ZhS6K Superalloy

2015 ◽  
Vol 227 ◽  
pp. 349-352
Author(s):  
Bartosz Chmiela ◽  
Marta Kianicová ◽  
Maria Sozańska
Keyword(s):  
Phase Composition ◽  
Hot Corrosion ◽  
Electron Backscatter Diffraction ◽  
Aluminide Coating ◽  
Turbine Blades ◽  
Aircraft Engine ◽  
Combustion Gases ◽  
Nickel Based Superalloy ◽  
Before And After ◽  
Primary Carbides

We considered the degradation of hollow turbine blades made of ZhS6K nickel-based superalloy after service in an aircraft engine. The blades were coated with a diffusive aluminide coating (Al-Si) to improve resistance to oxidation and hot corrosion. Turbine blades work under extreme conditions and a complex state of stress. During service, creep and fatigue occur. The interaction among hot combustion gases causes oxidation of the surface layer, hot corrosion, and micro-cracking of the coating. Moreover, changes occur in the morphology of theγ’phase just under the coating, and transformations of the primary carbides take place. The factors limiting the lifetime of a turbine blade are the quality of the aluminide coating and the microstructure of the superalloy, depending on the service parameters (the temperature and the duration service). We found that exposure to high temperatures above the critical value for several seconds substantially decreased the engine power and its durability. We analysed the microstructure, chemical composition, and phase composition of turbine blades after service. An evaluation of the extent of degradation was performed using scanning electron microscopy (SEM), energy dispersive X-ray microanalysis (EDS), and electron backscatter diffraction (EBSD). The EBSD technique was used to analyse the phase composition in micro-areas, especially to identify carbides before and after transformations.

Segregation of Alloying Elements of Directionally Solidified Nickel Based Superalloy CM247LC during Creep Degradation Process

2007 ◽  
Vol 353-358 ◽  
pp. 537-540 ◽  
Author(s):  
Takahiro Niki ◽  
Kazuhiro Ogawa ◽  
Tetsuo Shoji
Keyword(s):  
Chemical Composition ◽  
Degradation Mechanism ◽  
Axial Stress ◽  
Degradation Process ◽  
Propagation Path ◽  
Directionally Solidified ◽  
Nickel Based Superalloy ◽  
Segregation Of Alloying Elements ◽  
Local Enrichment ◽  
Creep Degradation

The mechanism of the degradation process of nickel based superalloy CM247LC under creep loading was analyzed by considering the microscopic chemical composition of the material such as phase boundary of γ and γ’ phases. In this study, a Directionally Solidified (DS) nickel-based superalloys CM247LC was used as test specimens. The creep test was performed at 900oC under an uni-axial stress of 216 MPa. Each specimen was creep ruptured and interrupted at different hours and then analyzed. The change of chemical composition around the interface analyzed precisely by used Auger Electron Spectroscopy (AES). It was found that the local enrichment or lack of cobalt and chromium was found at the interface. This tendency was not found in the stress free area. Since chromium is the well-known element that dominates the degradation of this material, such an enrichment or lack of cobalt and chromium may play an important role for forming a crack propagation path near the interface. This local segregation should be analyzed further to make clear degradation mechanism of this material.

High-temperature hot-corrosion effects on the creep–fatigue behavior of a directionally solidified nickel-based superalloy: Mechanism and lifetime prediction

2019 ◽  
Vol 29 (5) ◽  
pp. 798-809
Author(s):  
Shaolin Li ◽  
Xiaoguang Yang ◽  
Hongyu Qi
Keyword(s):  
High Temperature ◽  
Hot Corrosion ◽  
Damage Accumulation ◽  
Fatigue Behavior ◽  
Coated Sample ◽  
Directionally Solidified ◽  
Accumulation Model ◽  
Nickel Based Superalloy ◽  
Creep Fatigue ◽  
Damage Accumulation Model

Creep–fatigue experiments were performed at 850℃ on bare and salt-coated directionally solidified Ni-based superalloy DZ125. Experimental test results showed that the salt-coated sample exhibited lower lifetime than that of the bare sample under all stress conditions. This reduction is found to correlate directly with the higher probability of crack initiation, due to surface micro-structural degradation and higher actual stress as a result of the decrease in effective bearing area. A modified damage accumulation model considering the creep, fatigue, and hot-corrosion interaction effect was proposed to predict the corrosion–creep–fatigue lifetime. In this model, a critical high-temperature hot-corrosion exposure time was proposed and was introduced using the Miller linear damage accumulation model. The predicted lifetimes correspond remarkably well with the experimental results.

scholarly journals Corrosion Resistance Evaluation of Some Stainless Steels Used in Manufacture of Hydraulic Turbine Runner Blades

2019 ◽  
Vol 70 (7) ◽  
pp. 2491-2496 ◽  
Author(s):  
Cristian Predescu ◽  
Andrei Constantin Berbecaru ◽  
George Coman ◽  
Mirela Gabriela Sohaciu ◽  
Andra Mihaela Predescu ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Chemical Composition ◽  
Corrosion Rate ◽  
Stainless Steels ◽  
Turbine Blades ◽  
Hydraulic Turbine ◽  
Resistance Testing ◽  
General Corrosion ◽  
Steel Grades ◽  
Corrosion Pits

The paper presents corrosion resistance testing results of three stainless steels that may be used in hydropower turbine blades manufacture. Two of these have a chemical composition close to that of some other stainless steels previously employed in producing these parts, being updated steel grades of the former ones. The third one is of a new conception, having a chemical composition close to that of a maraging steel. The three materials were produced in an induction furnace with cold copper crucible under vacuum and argon atmosphere in order to obtain improved mechanical and corrosion resistance characteristics as well as an inclusion � free structure. Quenching and tempering heat treatments were subsequently applied. Tests were carried out at room temperature in normally aerated 1N Na2SO4 and 3% NaCl solutions. Corrosion rates were calculated using the Tafel slope method. All steels have a passivation tendency in a chlorine-free aqueous medium. The newly conceived steel has a more pronounced anodic field as a result of a chromium content below 12%. However, the general corrosion behavior of this material is rebalanced by the content of about 10% Ni which leads to a mainly martensitic structure in quenched state. The corrosion rate values obtained for all samples enframe the three materials in highly and very highly corrosion resistant steels. Nevertheless it must be specified that in chlorine environments the overall corrosion rate is not a sensitive indicator of corrosion resistance performance due to the local depassivation process followed by corrosion pits.

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