scholarly journals High Temperature Strength. General (Vertical) and Objective (Horizontal) R & D on Heat-Resistant Materials-Taking the Case of Superalloys for Gas Turbines.

1997 ◽  
Vol 46 (1) ◽  
pp. 2-6
Author(s):  
Ryuichi OHTANI
2009 ◽  
Vol 147-149 ◽  
pp. 744-751 ◽  
Author(s):  
Józef Błachnio

Heat-resistant and high-temperature materials are used to manufacture components, devices, and systems operated at high temperatures, i.e. under severe heat loads. Gas turbines used in the power industry, the traction, marine, and aircraft engines, the aerospace technology, etc. are good examples of such systems. Generally, as the temperature increases, the mechanical strength of materials decreases. While making such materials, there is a tendency to keep possibly low thermal weakening. In the course of operating gas turbines, various kinds of failures/defects/ damages may occur to components thereof, in particular, to blades. Predominating failures/damages are those attributable to the material overheating and thermal fatigue, all of them resulting in the loss of mechanical strength. The paper has been intended to present findings on changes in the microstructure of blades made of nickel-base alloy due to high temperature. The material gets overheated, which results in the deterioration of the microstructure’s condition. The material being in such condition presents low high-temperature creep resistance. Any component, within which such an effect occurs, is exposed to a failure/damage usually resulting in the malfunctioning of the turbine, and sometimes (as with aero-engines) in a fatal accident. Failures/damages of this kind always need major repairs, which are very expensive.


2019 ◽  
Vol 969 ◽  
pp. 34-40
Author(s):  
R. Ravibharath ◽  
K. Devakumaran ◽  
V. Muthupandi

Ni based super alloy 617 is widely used in transition liners in both aircraft and land-based gas turbines, power plant applications because of its high temperature strength, oxidation resistance and creep properties. Ni based alloys are highly susceptible to hot cracking like solidification and liquation racking issues. In this present work, the susceptibility of alloy 617 to solidification cracking is studied based on the varestraint test. Results of this weldability test proved that in addition to the solidification cracking susceptibility alloy 617 is prone to liquation cracking also. Keywords: Varestraint test, Alloy 617, Solidification cracking, Liquidation cracking.


2013 ◽  
Vol 32 (6) ◽  
pp. 563-572 ◽  
Author(s):  
N. Nabiran ◽  
S. Weber ◽  
W. Theisen

AbstractFerritic heat-resistant steels are commonly used for automotive exhaust systems and have replaced cast iron, the traditional material for this application. Efforts to improve the efficiency of engines, reduce weight, and minimize toxic ingredients by increasing the gas temperature have shifted the requirement for ferritic heat-resistant steels to a higher hot strength. Methods of improving the high-temperature strength are solid-solution strengthening, precipitation hardening, and grain refinement. In this work, the influence of MX precipitates on the high-temperature mechanical properties of three different ferritic Fe-Cr stainless steels was investigated and compared to a reference material. Investigations were performed with uniaxial compression tests of samples aged isothermally at 900 °C for up to 1440 h. The most effective method of increasing the high-temperature strength is to alloy the steel with 2 mass% tungsten. Grain growth during annealing at 900 °C was decelerated by solid-state formation of MX carbonitrides. Microstructural investigations also revealed a slow coarsening rate of the MX precipitates.


2011 ◽  
Vol 275 ◽  
pp. 117-120
Author(s):  
Keun Bong Yoo ◽  
Han Sang Lee ◽  
Kyu So Song

Gas turbine components operated by hot combustion gas undergo material degradation due to the thermal cycle by daily startup and shutdown. The failure mechanism of the hot gas components is accompanied by degradation in the properties of high temperature strength and creep rupture time. Many hot gas components in gas turbines are made of Ni-based superalloy because of their high temperature performance. In this work, we survey the time and temperature dependent degradation of Ni-based superalloy. We prepared specimens from Inconel738LC that were then exposed at 871~982°C in 1,000~5,000hours. We carried out stress-rupture tests and microstructural investigation.


Author(s):  
H. Yamamoto ◽  
M. Yamamoto ◽  
K. Imai ◽  
M. Miyazaki ◽  
M. Satoh ◽  
...  

The development of large single crystal and directionally solidified hollow and solid bucket castings has been carried out for the high performance advanced land-based gas turbine of 1500°c class turbine inlet temperature, using CMSX-2 single crystal and CM247LC directionally solidified alloys*. The castability for large single crystal bucket casting has been established by optimizing the casting parameters and bucket shape in order to prevent the grain defects which tend to be formed more easily for larger casting size and are most harmful for high temperature strength of single crystal. These casting processes were successsfully applied to larger directionally solidified buckets with additional modified molding process. The developed large single crystal hollow and solid bucket castings after solution and optimized aging treatment indicated excellent microstructure and high temperature mechanical properties such as stress rupture and low cycle fatigue strength. Also, long-term phase stability of both alloys at intermediate temperatures has been verified.


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