Coarsening Behavior of Precipitates in a Conventional Cast Nickel Base Superalloy during Long Term Thermal Exposure

2014 ◽  
Vol 788 ◽  
pp. 452-458
Author(s):  
Qiang Zeng ◽  
Ping Yan ◽  
Jing Chen Zhao ◽  
Long Fei Zhang ◽  
Lian Li
Keyword(s):  
Aging Time ◽  
Early Stage ◽  
Aging Treatment ◽  
Thermal Exposure ◽  
Nickel Base Superalloy ◽  
Coarsening Behavior ◽  
Nickel Base ◽  
The One ◽  
Base Superalloy

A long term aging treatment at 900oC for 3000h was carried out on a conventional cast nickel base superalloy with standard solution and aging treatment. The microstructural evolution including the phases within grains and at grain boundaries (GBs) during thermal exposure in the alloy was observed using OM and SEM. It was shown that the major phases in the alloy after standard heat treatment were γ' precipitates and coarse blocky MC carbides, both of which were distributed not only within grains but also at GBs. During aging, the size of MC carbides and γ' precipitates both within grains and at GBs increased with increasing aging time. It was found that two characteristics of MC carbide and γ' precipitates evolved with aging time: the one is that the coarsening ratio of carbides and γ' precipitates at GBs were significantly higher than that of carbide and γ' precipitates inside the grains; the other is that the coarsening ratio of carbides was markedly higher than that of γ' precipitates. M6C carbide and η phase initially formed in the edge of MC carbide at the expense of MC carbides and γ' precipitates in the vicinity of MC during the early stage of aging. After 3000h, MC carbides inside the grains were covered by η phase films, while those distributed at GBs were completely decomposed into η phase and M6C particles.

Effect of Long-Term Aging on Microstructural Restoration in Cast Nickel Base Superalloy, GTD-111

2017 ◽  
Vol 891 ◽  
pp. 426-432 ◽  
Author(s):  
Chuleeporn Paa-Rai ◽  
J. Norachan ◽  
Panyawat Wangyao ◽  
Sureerat Polsilapa ◽  
Gobboon Lothongkum
Keyword(s):  
Aging Time ◽  
Research Study ◽  
Volume Fraction ◽  
Area Fraction ◽  
Nickel Base Superalloy ◽  
Final Microstructure ◽  
Reheat Treatment ◽  
Nickel Base ◽  
Base Superalloy

In this research study, the effect of long-term aging after various solutioning temperatures on final microstructure was investigated. The cast nickel base superalloy, GTD-111, usually has standard reheat treatment as follows: solutioning treatment at 1448 - 1478 K for 7.2 ‑ 21.6 ks and aging at 1118 K for 86.4 ks. However, from previous research works, the density of γ՛ phase was not reached the optimum value. Therefore, extension of aging time was performed in the study from 90 to 180, 270, 360, 720, 1080 and 1440 ks in order to increase density or volume fraction of precipitating γ՛ particles. From the results, it was found that longer aging time provided higher values of both area fraction and size of γ՛ particles. However, increase in aging time resulted in the hardness decrease.

Effect of Thermal Exposure on Long-Term Heated Microstructures at 900°C of Nickel Base Superalloy Turbine Blade, Grade Inconel 738

2015 ◽  
Vol 658 ◽  
pp. 19-24
Author(s):  
Panyawat Wangyao ◽  
Sureerat Polsilapa ◽  
Surang Singmaneesakulchai ◽  
Aimamorn Promboopha
Keyword(s):  
Heat Treatment ◽  
Working Conditions ◽  
Turbine Blades ◽  
Thermal Exposure ◽  
Stable Phase ◽  
Nickel Base Superalloy ◽  
Gamma Prime ◽  
Nickel Base ◽  
Base Superalloy

The objectives of this research are to search for the most appropriate heat treatment condition for rejuvenating microstructure of cast nickel base superalloy, grade IN-738, turbine blades after using to prolong its life time service again. The turbine blades that had been used for long term service under load and high temperatures resulted in small gamma prime particles connecting to each other and thus forming into larger particles. This effect generally reduces creep resistance and increases the failure. In this research, 5 IN-738 superalloy samples were reheat-treated under simulation of 2 working conditions. First, they were heated at 900oC. At every 400 hours from the beginning of heat treatment until time reaching 1600 hours, these samples were collected and examined the microstructures, size and area fraction of gamma prime particles. Another heating program, they received an over thermal exposure heating at 1125oC for 1 hour after long-term heated at 900oC after every 400 hours-heating. Then the results were analyzed from working conditions. It was found that the sample passed solutioning at 1125oC for 4 hours and aging at 845oC for 24 hours with the over thermal exposure showed the most stable phase stability with γ’ phase increasing after long-term simulated working conditions .

Effect of Pre-Weld Heat Treatment Temperatures on TIG Welded Microstructures on Nickel Base Superalloy, GTD-111

2015 ◽  
Vol 658 ◽  
pp. 14-18
Author(s):  
Tanaporn Rojhirunsakool ◽  
Duangkwan Thongpian ◽  
Nutthita Chuankrerkkul ◽  
Panyawat Wangyao
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Heat Treatment Temperature ◽  
Treatment Temperature ◽  
Tig Welding ◽  
Nickel Base Superalloy ◽  
Nickel Base ◽  
Base Superalloy ◽  
Weld Heat

Nickel-base superalloys have been used as high temperature materials in land-base gas turbine application. When subjected to long term, high temperature service, large crack propagation was observed. Typical refurbishment method of these turbines is carried out by using TIG welding followed by post-weld standard heat treatment. However, new crack initiation is found in the heat-affected zone after TIG welding. Pre-weld heat treatment has been discovered to improves final γ + γ’ microstructure. This study focuses on the effect of pre-weld heat treatment temperature on final γ + γ’ microstructure. Seven different conditions of pre-weld heat treatment temperature were investigated. Scanning electron microscopy studies were carried out after pre-weld and post-weld heat treatments to compare the γ + γ’ microstructure and capture microcracks. The best pre-weld heat treatment temperature produces uniform distribution of finely dispersed γ’ precipitates in the γ matrix without post-weld crack.

Microstructural evolution of a single crystal nickel-base superalloy during thermal exposure

2003 ◽  
Vol 57 (29) ◽  
pp. 4540-4546 ◽  
Author(s):  
L.R. Liu ◽  
T. Jin ◽  
N.R. Zhao ◽  
Z.H. Wang ◽  
X.F. Sun ◽  
...  
Keyword(s):  
Single Crystal ◽  
Microstructural Evolution ◽  
Thermal Exposure ◽  
Nickel Base Superalloy ◽  
Nickel Base ◽  
Base Superalloy

Effect of Precipitation Aging Temperatures on Reheat Treated Microstructures and its Phase Stability after Long-Term Exposure in Cast Nickel Base Superalloy, Grade Inconel 738

2017 ◽  
Vol 891 ◽  
pp. 433-437 ◽  
Author(s):  
Nattapol Kontikame ◽  
Sureerat Polsilapa ◽  
Panyawat Wangyao
Keyword(s):  
Phase Stability ◽  
Power Plants ◽  
Turbine Blades ◽  
Research Work ◽  
Nickel Base Superalloy ◽  
Gamma Prime ◽  
Treatment Conditions ◽  
Nickel Base ◽  
Base Superalloy

This research work has an aim to investigate the effect of precipitation aging temperatures of 845°C, 865°C, 885°C and 905°C for 24 hours after solutioning treatment at temperature of 1145°C for 4 hours on final microstructure of cast nickel base superalloy, grade Inconel 738, which is used as a material for turbine blades in land base gas turbine engines to generate electricity in power plants. Further interesting is also extended to study and evaluate the phase stability of precipitated gamma prime particles after long-term heating at tempeatures of 900°C and 1000°C for 200 hours of all received final microstructures after various reheat treatment conditions. From all obtained results, it was found that the higher precipitation aging temperatures provided the more coarsening size of both coarse and fine gamma prime particles. Furthermore, after long-term exposure at high temperatures, this resulted in an increasing of both area density and size of gamma prime particles.

Long-Term Gamma Prime Phase Stability after Various Heat Treatment Conditions with Temperature Dropping during Solution Treatment in Cast Nickel Base Superalloy, Grade Inconel-738

2017 ◽  
Vol 891 ◽  
pp. 420-425
Author(s):  
Sureerat Polsilapa ◽  
Aimamorn Promboopha ◽  
Panyawat Wangyao
Keyword(s):  
Heat Treatment ◽  
Turbine Blades ◽  
Solution Treatment ◽  
Nickel Base Superalloy ◽  
Gamma Prime ◽  
Nickel Based Superalloy ◽  
Treatment Conditions ◽  
Nickel Base ◽  
Base Superalloy

Cast nickel based superalloy, Grade Inconel 738, is a material for turbine blades. Its rejuvenation heat treatment usually consist of solution treatment condition with temperature range of 1125-1205 oC for 2-6 hours. Then it is following with double aging process including primary aging at 1055oC for 1 hour and secondary aging at 845oC for 24 hours. However, the various selected temperature dropping program were performed during solution treatment to simulate the possible error of heating furnace. The maximum number of temperature dropping during solution treatment is varied from 1-3 times From all obtained results, the various temperature dropping during solution treatment conditions showed extremely the significant effect on the final rejuvenated microstructures and long-term gamma prime stability after heating at temperature of 900oC for 200 hours.

Coarsening Kinetics of Grain Boundary in a Cast Nickel Base Superalloy during Long Term Aging

PRICM ◽  
2013 ◽  
pp. 317-325
Author(s):  
Qiang Zeng ◽  
Minghan Zhao ◽  
Ping Yan ◽  
Juntao Li ◽  
Jingchen Zhao ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Nickel Base Superalloy ◽  
Coarsening Kinetics ◽  
Nickel Base ◽  
Kinetics Of ◽  
Base Superalloy
Sign in / Sign up

Export Citation Format

Share Document