Investigation on Creep Mechanism of a Ni3Al-Based Single Crystal Superalloy IC6SX under 760°C/540MPa

2013 ◽  
Vol 747-748 ◽  
pp. 804-809 ◽  
Author(s):  
Li Wu Jiang ◽  
Shu Suo Li ◽  
Mei Ling Wu
Keyword(s):  
Electron Microscopy ◽  
Single Crystal ◽  
Creep Mechanism ◽  
Single Crystal Superalloy ◽  
Creep Process ◽  
Dislocation Configuration ◽  
Creep Stage ◽  
Dislocation Glide ◽  
Accelerated Creep ◽  
Testing Condition

The creep behaviors of a Ni3Al-base single crystal superalloy IC6SX prepared by spiral grain selection method was studied systematically under the testing condition of 760/540MPa. The microstructure evolution, movement of dislocations, formation of the dislocation networks and dislocation configuration during the creep process were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the creep performance of the single crystal alloy IC6SX is excellent under 760/540MPa. The experimental results showed that the creep curve of the Ni3Al-base single crystal superalloy IC6SX was divided into three stages, including decelerating creep stage, steady-state creep stage and accelerated creep stage. The microstructure and the dislocation configuration were different at different stage during the creep and the raft microstructure has not been formed. The creep mechanism was main slipping characterized by dislocation glide mechanism.

Creep Properties and Microstructural Evolution at 760°C/785MPa of a Re-Containing Single Crystal Superalloy

2019 ◽  
Vol 944 ◽  
pp. 8-12
Author(s):  
Yun Song Zhao ◽  
Yan Fei Liu ◽  
Jing Xuan Zhao ◽  
Xiao Tie Zhang ◽  
Yan Yang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Single Crystal ◽  
Microstructural Evolution ◽  
Rupture Life ◽  
Turbine Blades ◽  
Creep Rupture ◽  
Single Crystal Superalloy ◽  
Creep Tests ◽  
Dislocation Configuration ◽  
Creep Properties

Intermediate temperature creep properties are considered a key indicator of single crystal superalloys used for turbine blades of aircraft engines. The interrupted and ruptured creep tests were carried out in a second generation single crystal superalloy under the conditions of 760°C/785MPa. The creep rupture life as well as minimum creep rate were also in the same level of those in CMSX-4 and PWA1484. The microstructural evolution at different creep stages were analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed the γ’ phases kept the cuboid morphology mostly until the creep rupture, and super lattice stacking faults (SSFs) extended along [-1 1 0] and [-1-1 0] orientations within the γ’ precipitate were the typical dislocation configuration.

scholarly journals Formation and evolution of porosity during high temperature creep of a nickel-based single crystal superalloy

2020 ◽  
Vol 155 ◽  
pp. 01005
Author(s):  
Weiwei Liu ◽  
Yuanyuan Guo ◽  
Mai Zhang ◽  
Jian Zhang
Keyword(s):  
Electron Microscope ◽  
High Temperature ◽  
Single Crystal ◽  
Volume Fraction ◽  
Great Influence ◽  
Single Crystal Superalloy ◽  
Creep Process ◽  
Steady Creep ◽  
Transmission Electron ◽  
Formation And Evolution

A Re-containing single-crystal superalloy was used to research the high temperature low stress creep behavior. Transmission electron microscope, scanning electron microscope and some other research methods are employed. The results and analysis are summarized below: Two mechanisms for the steady creep are found in this experiment. The volume fraction of pores after creep test at 1100°C increased more than 2 times compared with that before test, but the increasing at 1000°C is relatively small, which reveals that temperature has an great influence on the formation of pore during creep; There are two types of pores associated with fracture during the creep process. One is the casting shrinkage located between the interdentritic, which is formed in the solidification of the alloy. Another type of pore is nucleated and growing during the creep deformation.

Microstructural Evolution of Nuclear Power Steel A508-III in the Creep Process at 800°C

2016 ◽  
Vol 853 ◽  
pp. 153-157
Author(s):  
Zhi Gang Xie ◽  
Yan Ming He ◽  
Jian Guo Yang ◽  
Zeng Liang Gao
Keyword(s):  
Electron Microscopy ◽  
Phase Transition ◽  
Grain Size ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Microstructural Evolution ◽  
Creep Process ◽  
Second Phase ◽  
Creep Stage ◽  
Second Phase Particles

The A508-III steel is widely used to manufacture the lower heads of commercial reactor pressure vessels (RPV). In severe accident, the reactor core in the RPV begins to melt and meanwhile the technology of in-vessel retention (IVR) exerts its role. In this case the inner surface of RPV will expose to temperatures over a phase transition temperature. However, the significant nonlinear feature of creep curve of A508-III steel suffered heterogeneous damage was not studied. In this work, the creep tests were performed for the steel at the phase transition temperature of 800°C. The microstructural evolution at different creep stages was characterized by scanning electron microscopy and transmission electron microscopy. The results show that, at the second creep stage, more coarsening second phase particles occur in the steel. With the creep processing, the grain size and diameter of second phase particles increase. At the tertiary creep stage, the grain size increases significantly, and the second phase particles coarsen during the process of atom migration. In addition, Micro-cracks and voids also come into being in the situation and they can become larger by combing each other during the creep process. At this stage, the growth of cavities and second phase particles coarsening become the main mechanism of creep damage. The trend of microstructural evolution is consistent with the creep constitutive equation obtained for the A508-III steel at the phase transition temperature of 800°C. The results obtained provide indispensable foundation to establish the relationship between the macroscopic creep and microscopic damage.

scholarly journals Microstructure investigations of Pt-modified γ′-Ni3Al + γ-Ni coatings on Ni-based superalloys

2010 ◽  
Vol 25 (6) ◽  
pp. 1191-1195 ◽  
Author(s):  
Guanghui Cao ◽  
Taoping Ou ◽  
Hua Jiang ◽  
Alan M. Russell
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Single Crystal ◽  
Energy Dispersive ◽  
Single Crystal Superalloy ◽  
Refractory Element ◽  
Cross Sectional ◽  
X Ray ◽  
Topologically Close Packed ◽  
Transmission Electron

The microstructure of Pt-modified γ′-Ni3Al + γ-Ni coating on CMSX-4 single-crystal superalloy has been investigated by transmission electron microscopy (TEM). Cross-sectional TEM analyses showed the presence of precipitates in the coating. This precipitate was identified as the hexagonal topologically close-packed (TCP) μ phase with lattice parameters a = 0.473 nm and c = 2.565 nm. The energy-dispersive x-ray (EDX) spectrum of the μ phase suggested a refractory element rich compound comprising the elements Re, W, and Co. Twin domains parallel to (001) were found in the μ phase. The mechanisms of the μ phase and twinning formation were discussed.

A Methodology for Evaluation of Life Fraction Using Cr-Mo Steel under Creep Conditions

2013 ◽  
Vol 758 ◽  
pp. 57-63
Author(s):  
Marcelo A. da Silva ◽  
José Claudio G. Teixeira ◽  
Ari Sauer Guimarães ◽  
Ivani S. Bott ◽  
Hector R.M. Costa
Keyword(s):  
Electron Microscopy ◽  
Microstructural Evolution ◽  
Residual Life ◽  
Constant Load ◽  
Creep Process ◽  
Tem Analysis ◽  
Transmission Electron ◽  
Accelerated Creep ◽  
The Relationship ◽  
Life Fraction

The quantification methodology used to predict the residual life of Cr-Mo steel was microstructure/life fraction correlation under creep conditions. Microstructural evolution has been correlated with accelerated creep testing progress during testing at constant load and a temperature of 600°C, as well as with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis. Experimental results from TEM revealed six distinct stages, which were directly related to the life fraction values obtained. However, in the case of MEV, five stages were found. This difference is likely due to the better analysis possible via TEM of both microstructural evolution and types of carbides formed during the creep process. In addition, an evolution map is proposed to allow for easy interpretation of the relationship between microstructural characteristics and life fraction.

Creep Behavior of a Ru-Free Nickel-Based Single Crystal Superalloy at Medium Temperatures

2017 ◽  
Vol 893 ◽  
pp. 212-217 ◽  
Author(s):  
Shuang Liang ◽  
Zhi Xin Liu
Keyword(s):  
Single Crystal ◽  
Creep Behavior ◽  
Diffusion Rate ◽  
Stacking Fault ◽  
Single Crystal Superalloy ◽  
Effect Factors ◽  
Dislocation Configuration ◽  
Screw Dislocations ◽  
Creep Curves ◽  
Contrast Analysis

By means of creep curves measurement and diffraction contrast analysis of dislocation configurations, the creep behavior and effect factors of a Ru-free nickel-based single crystal superalloy within the temperature range of 740~780°C are investigated. Results indicated that, the cubical γ′ phase transformed into the bunch-like structure. During creep at 760°C/750Mpa, no rafted features of γ′ phase is detected, but the degree of distortion of the cubic γ′ phase near fracture regions is increased. During creep, more super-dislocations shearing into γ′ phase of Ru-free alloy are decomposed on {111} plane to form the partials plus stacking fault, which is attributed to the interaction of the elements to decrease the stacking fault energy of the alloy. Moreover, the screw dislocations shearing into γ' phase of Ru-free alloy during creep at 760 °C may cross-slip from {111} to {100} planes for decomposing to form the configuration of the K-W locks, which is attributed to the higher alloying extent for decreasing the diffusion rate of elements. And the dislocation configuration may restrain the slipping of them to improve the creep resistance of alloy due to the non-plane core structure of them.

Effect of Temperature on Formation of Borides in TLP Joint of a Kind of Nickel-Base Single Crystal Superalloy

2007 ◽  
Vol 546-549 ◽  
pp. 1245-1248 ◽  
Author(s):  
J.D. Liu ◽  
Tao Jin ◽  
N.R. Zhao ◽  
Z.H. Wang ◽  
Xiao Feng Sun ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Single Crystal ◽  
Base Metal ◽  
Room Temperature ◽  
Bonding Temperature ◽  
Single Crystal Superalloy ◽  
Effect Of Temperature ◽  
Transmission Electron ◽  
Different Temperatures ◽  
Nickel Base

a kind of as-cast nickel-base single crystal superalloy was TLP bonded using Ni-Cr-B amorphous foil at different temperatures. Special attention is paid to the formation of boride in diffusion zone of TLP joints at different conditions. The chemical composition and microstructure of borides were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). At different bonding temperature, M3B2 precipitates appear distinct morphologies. At 1200°C, both blocky and plate-like borides formed owing to the diffusion of boron atoms into base metal and precipitation during the cooling process. At 1230°C or above, due to the diffusion of boron atoms the constitutional liquation of original γ/γ′ eutectics in the base metal occurs and borides formed when the system was cooled to room temperature. The analysis of TEM results reveals that M3B2 has a tetragonal structure and is rich in Mo, W, and Cr elements.

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