The Use and Performance of Wrought 625 Alloy in Primary Surface Recuperators for Gas Turbine Engines

Rakowski, James M.; Stinner, Charles P.; Lipschutz, Mark; Montague, J. Preston

doi:10.7449/2005/superalloys_2005_271_286

Cited by 8 publications

(2 citation statements)

References 16 publications

(19 reference statements)

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“…The Cr depletion and mass gain results are consistent with volatilization and the accelerated Cr loss in the While the mass changes in Figure 1 are relatively small, at longer times and higher temperature, the accelerated Cr depletion due to the presence of water vapor can be significant. Alloy 625 foil has been used for high temperature recuperators to improve the efficiency of small turbines [28], including the recuperator for the 24 MW WR21 marine turbine and a 4.5 MW landbased turbine [29,30]. In addition to creep strength, the presence of water vapor limits the maximum operating temperature of alloy 625 in this application.…”

Section: Effect Of Water Vapor On Oxidationmentioning

confidence: 99%

Oxidation of Superalloys in Extreme Environments

Pint¹,

Dryepondt²,

Unocic³

2010

Superalloy 718 and Derivatives

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With the current interest in increased efficiency and reduced emissions, materials in power generation systems are increasingly exposed to more aggressive environments and higher temperatures. It is important to understand how these environments can increase corrosion rates, possibly reducing performance and likely shortening component lifetimes. Superalloys like 718 and its derivatives primarily rely on the formation of an external Cr-rich oxide layer or scale for environmental protection at typical application temperatures (≤700°C). While many laboratory oxidation and creep experiments are conducted in ambient air, the application environment for these alloys often involves combustion products, such as H 2 O and CO-CO 2 . The effect of these environments is not completely understood, especially the impact of long-term exposures, typically required of superalloy components in turbines. Air and fuel impurities, especially S and Na, can result in accelerated degradation such as the well known hot corrosion attack. While the effect of environment on crack growth has been studied, less information is available on the effect of environment on creep and fatigue properties. Initial work is being conducted to better understand the role of environment on creep properties, eventually including in-situ testing. Examples are given from steam and wet air environments and comparisons of different superalloy compositions with cast versus wrought microstructures.

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Section: Effect Of Water Vapor On Oxidationmentioning

confidence: 99%

Oxidation of Superalloys in Extreme Environments

Pint¹,

Dryepondt²,

Unocic³

2010

Superalloy 718 and Derivatives

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“…Inconel™ 625 is a nickel-based superalloy developed close to 60 years ago to achieve a good combination of mechanical strength, fracture toughness, fabricability, weldability and corrosion resistance under aggressive environments both at room and high temperatures [1,2]. This alloy is widely used in the petrochemical, marine, nuclear, power generation and aerospace industries [1][2][3][4][5][6][7]. In the aerospace industry, Alloy 625 is used as turbine shrouds, spray bars, hydraulic tubing, armoring and thrust reversers systems.…”

Section: Introductionmentioning

confidence: 99%

Impact of Thermomechanical Aging on Alloy 625 High Temperature Mechanical Properties

Suave¹,

Soula²,

Bertheau³

et al. 2014

8th International Symposium on Superalloy 718 and Derivatives (2014)

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Alloy 625 is widely used for petrochemical, marine and aerospace applications owing to its outstanding corrosion and mechanical properties at high temperatures. However, this alloy is prone to complex microstructure evolutions above 500°C that may impact its mechanical properties. In this study, the impact of its micro structure evolutions occurring upon long-term thermal aging on its static and cyclic mechanical properties has been studied. Thermal exposures of up to ~ 2000 hours in the 550°C-900°C temperature range have been investigated. TTT diagrams of the 5 and y" phases were established based on high resolution scanning electron microscopy observations. The evolutions of secondary carbides distributions were also followed. It has been observed a steep increase of the room temperature microhardness after overagings performed at 650°C and 700°C due to the precipitation of the y" phase. Moreover, it is also clearly evidenced a strengthening effect of the 5 phase after long-term thermal exposures at temperatures in excess of 700°C. Finally, the impact of a thermal aging in the y" precipitation domain on the high temperature tensile and low cycle fatigue properties was evaluated. It is shown a beneficial effect of the y' ' precipitation to the fatigue life and to the tensile properties up to 750°C. It is also shown that the loss of high temperature ductility is not correlated to the precipitation of grain boundary secondary carbides. y'' precipitation and the y'' ^5 transformation are also shown to be faster under cyclic loading compared to pure thermal aging.

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