Microstructure Development of an Electroplating Coated Nickel-Base SC Superalloy in Oxidation Processes—Simulation Results

2021 ◽  
Author(s):  
Kang Yuan ◽  
Zhaoran Zheng
Keyword(s):  
Kinetic Model ◽  
Single Crystal ◽  
Diffusion Zone ◽  
Microstructure Development ◽  
Diffusion Kinetic ◽  
Oxidation Processes ◽  
Secondary Reaction Zone ◽  
Tcp Phases ◽  
Simulation Results ◽  
Nickel Base

Abstract In this paper; a diffusion kinetic model was applied to simulate the microstructure development in a MCrAlY-superalloy system at high temperatures. Both simulation and experimental results showed that γ+γ’ microstructure was obtained in the coatings due to Al depletion after oxidation. With the help of the modelling; the mechanism of the formation of the diffusion zones in the single crystal (SC) superalloy can be also analyzed. The results revealed that the inward diffusion of Al from coating affected the depth of secondary reaction zone (SRZ) with the precipitation of TCP phases while the depth of inter-diffusion zone (IDZ) was decided by the inward diffusion of Cr.

scholarly journals A Study of the Effects of Alloying Additions on TCP Phase Formation in 4th Generation Nickel-Base Single-Crystal Superalloys

2011 ◽  
Vol 278 ◽  
pp. 54-59 ◽  
Author(s):  
H.T. Pang ◽  
R.A. Hobbs ◽  
Howard J. Stone ◽  
Catherine M.F. Rae
Keyword(s):  
Single Crystal ◽  
Detailed Analysis ◽  
Phase Formation ◽  
Environmental Performance ◽  
Elevated Temperatures ◽  
Turbine Blades ◽  
Alloying Additions ◽  
Tcp Phases ◽  
Tcp Phase ◽  
Nickel Base

The demand for higher engine operating temperatures to improve aeroengine efficiency has meant that increasing levels of alloying additions are being added to single-crystal nickel-base superalloys for turbine blades applications. Whilst better mechanical and environmental performance may be obtained with these alloying additions, they also destabilise the alloys forming topologically closed-packed (TCP) phases. In this study, the formation of TCP phases has been studied in a series of four alloys designated LDSX1-4 which have a systematic variation in the levels of Co, Mo and W. The alloys were exposed to elevated temperatures between 900-1100°C for up to 1000 hours. This was followed by detailed analysis of the microstructures in the SEM. Identification of the TCP phases in selected alloys was also carried out. The effects of each alloying addition on TCP phase formation is discussed in light of these results.

CMSX-4® Plus (SLS): An Improved 3rd Generation Single Crystal Alloy

2020 ◽  
Author(s):  
Jacqueline Wahl ◽  
Ken Harris
Keyword(s):  
Single Crystal ◽  
Phase Stability ◽  
Hot Corrosion ◽  
Base Alloy ◽  
Turbine Blades ◽  
Secondary Reaction Zone ◽  
High Temperature Mechanical Properties ◽  
Fuel Burn ◽  
And Performance ◽  
Nickel Base

Abstract Ongoing demand for advanced aero gas turbine engines with lower fuel burn and commensurate reduced CO2 emissions require single crystal (SX) superalloys capable of operating at higher gas and metal temperatures beyond the capability of 2nd generation, 3% rhenium (Re)-containing SX alloys, currently used extensively in commercial and military flight engines. These complex cooled turbine blades and vane castings must have an excellent balance of high temperature mechanical properties, producibility, oxidation/hot corrosion resistance, coating compatibility including TBC performance and phase stability. The highest strength nickel-base SX superalloys currently in production (3rd generation CMSX-10K® and CMSX-10N® alloys) contain 6–7% Re. These highly alloyed, specialty alloys have some application drawbacks including some secondary reaction zone (SRZ) phase instability in the base alloy adjacent to the coatings, low temperature internal oxidation/hot corrosion attack requiring sophisticated dual role internal and external coatings and difficulty in production solution heat treatment. In addition, current 3rd generation SX alloys have relatively higher density which is a disadvantage in terms of weight and inertia in rotating part applications, and high cost due to the elevated Re content. An improved, lower Re content (4.8%), 3rd generation SX superalloy, CMSX-4® Plus (SLS) has been developed with improved properties and performance over current 3rd generation SX alloys, while lacking the drawbacks. Coatings have been successfully developed which are compatible with the base alloy and suitable bond coats for TBC application. This paper presents the characterization of CMSX-4 Plus (SLS) alloy, including composition, mechanical and physical properties, oxidation properties and phase stability, along with production status.

scholarly journals Modeling of Precipitation Kinetics of TCP-Phases in Single Crystal Nickel-Base Superalloys

2011 ◽  
Vol 278 ◽  
pp. 180-185 ◽  
Author(s):  
Ralf Rettig ◽  
Astrid Heckl ◽  
Robert F. Singer
Keyword(s):  
Single Crystal ◽  
Multicomponent Diffusion ◽  
Interface Energy ◽  
Precipitation Process ◽  
Precipitation Model ◽  
Mobility Database ◽  
Tcp Phases ◽  
Tcp Phase ◽  
Nickel Base ◽  
Kinetics Of

The precipitation of brittle so-called TCP-phases is critical for the application of Re-containing single crystal superalloys. In this work a fully multicomponent precipitation model is presented, which is capable of simulating the precipitation process of the TCP-phases in superalloys considering complex precipitation sequences with several metastable phases. The model is coupled to multicomponent thermodynamic CALPHAD calculations and relies on multicomponent diffusion models based on the TC-API interface of the software DICTRA. The required mobility database has been newly developed and covers all relevant alloying elements of the Ni-base superalloys including rhenium (Re) and ruthenium (Ru). It is well known that adding Ru strongly reduces TCP-phase precipitation. Based on the developed precipitation model, possible mechanisms are investigated to explain this effect and it is concluded that Ru mostly influences the nucleation rate by a combined influence on interface energy, “reverse partitioning” and γ’-phase fraction.

Alloy Phase Stability Requirements in Single Crystal Superalloys

1990 ◽  
Vol 186 ◽  
Author(s):  
David N. Duhl
Keyword(s):  
Single Crystal ◽  
Phase Stability ◽  
Elevated Temperatures ◽  
Engine Performance ◽  
Two Phase ◽  
Gamma Prime ◽  
Tcp Phases ◽  
Nickel Base ◽  
Alloy Properties ◽  
Electron Vacancy

AbstractAlloy phase stability is a critical parameter in the design and implementation of nickel-base superalloys. To achieve the high temperature properties required of single crystal superalloys for application in gas turbine machinery, these alloys must have a stable gamma plus gamma prime microstructure for long periods of time at elevated temperatures. Significant deviation from this stable two phase microstructure, due to the precipitation of other phases, results in the loss of critical alloy properties which can have a deleterious impact on engine performance.Empirical methods based on the electron vacancy concept, commonly employed to predict and prevent the formation of undesirable topologically close packed (TCP) phases such as sigma or mu in polycrystalline nickelbase superalloys, are also used with single crystal superalloys. These undesirable phases result in the loss of alloy properties primarily as a result of the depletion of refractory strengthening elements from the superalloy matrix. The consequence of the formation of undesirable TCP phases on alloy properties and subsequent single crystal component behavior is reviewed.

New Phases in a Multicomponent High Ruthenium Single Crystal Superalloy

2005 ◽  
Vol 475-479 ◽  
pp. 655-660 ◽  
Author(s):  
Q. Feng ◽  
L.J. Rowland ◽  
T.M. Pollock
Keyword(s):  
Single Crystal ◽  
Dendritic Structure ◽  
Thermal Exposure ◽  
Single Crystal Superalloy ◽  
Heusler Phase ◽  
Topologically Close Packed ◽  
Tcp Phases ◽  
Δ Phase

Three unusual Ru-rich phases have been identified in a multicomponent Ni-base single crystal superalloy, including a L21 Ru2AlTa Heusler phase, a B2 RuAl phase and a hcp Re(Ru)-rich δ phase. These phases have their own preferential precipitation location within the dendritic structure. No conventional topologically-close-packed (TCP) phases have been observed with thermal exposure at 950oC for 1500 hours.

The Effect of Tensile Stress on Oxidation Behavior of Nickel-Base Single Crystal Superalloy

2021 ◽  
pp. 109737
Author(s):  
Hai-Qing Pei ◽  
Meng Li ◽  
Ping Wang ◽  
Xiao-Hu Yao ◽  
Zhi-Xun Wen ◽  
...  
Keyword(s):  
Tensile Stress ◽  
Single Crystal ◽  
Oxidation Behavior ◽  
Single Crystal Superalloy ◽  
Nickel Base
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