The Interaction of High Temperature Corrosion and Mechanical Properties of Alloys

Grünling, H.W.; Keienburg, Karl-Heinz; Schweitzer, K.

doi:10.1007/978-94-009-7907-9_20

Cited by 8 publications

(4 citation statements)

References 4 publications

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“…Crack propagation appears to be assisted strongly by the environment, with environmental attack ahead of the crack tip, and in some cases, propagation along grain boundaries that have been attacked by oxygen and sulfur. o Air (14,16) u Type I Hot Corrosion (16) a Type II Hot Corrosion [17,18] •…”

Section: Discussionmentioning

confidence: 99%

“…Floreen and Kane [111 have shown that the fatigue crack growth rate of IN-718 is greatly increased in air compared to helium, and that sulfur further accelerates the crack growth rate compared to air. Ericsson [12], Cook and Skelton [13], and Grunting, et al [14], have reviewed the effect of environment upon the mechanical properties of materials.…”

Section: Crack Initiation and Propagationmentioning

confidence: 99%

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Analysis of Cracked Gas Turbine Blades

Bernstein

Allen

1991

Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation;

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Results from an analysis of cracked first stage blades (or buckets) from two General Electric Frame 7001E industrial/electric utility gas turbines are presented. Numerous cracks were observed along the leading-edge and mid-chord regions of the pressure and suction surfaces. In one unit cracks were found after 874 start-stop cycles, which included 218 trips from load and 11,000 service hours. Buckets in the sister engine were examined after 1800 cycles, which included 218 trips from load and 24,000 service hours. In both cases, cracks initiated in the platinum aluminide coating and propagated into the IN-738LC base metal. For the 11,000-hour bucket, 20-mil (0.5-mm) deep cracks were observed, and for the 24,000-hour bucket, the leading edge cracks had grown to the leading edge cooling hole, a distance of 0.2 inches (5 mm). The number of cycles to crack initiation was in good agreement with thermal mechanical fatigue (TMF) predictions from the REMLIF computer program, which is part of the Electric Power Research Institute’s (EPRI) Life Management System. The cracking was greatly accelerated by the large number of trips experienced. The extensive crack propagation that occurred is thought to have been strongly assisted by oxygen and sulfur penetration along the grain boundaries. The coating on the leading edge degraded from the original platinum-aluminide plus beta phases to a gamma prime phase after 24,000 hours of service, but it was still protective except where it was cracked. Where the coating was cracked, environmental attack of the interdiffusion zone and base metal occurred, resulting in spallation of the coating and preferential grain boundary attack. Operating and maintenance considerations for optimizing bucket life in demanding cyclic duty environments are also discussed.

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Section: Discussionmentioning

confidence: 99%

Section: Crack Initiation and Propagationmentioning

confidence: 99%

Analysis of Cracked Gas Turbine Blades

Bernstein

Allen

1991

Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation;

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“…[1] Contrary to the formation of superficial scales, which in the case of Cr 2 O 3 and Al 2 O 3 protect the substrate against excessive corrosion attack, [2] internal corrosion may result in a deep deterioration of the physical properties of the material (e.g., creep resistance and high-temperature fatigue strength). [3,4] Figure 1 shows an example of internal oxidation (Al 2 O 3 ) and nitridation (AlN; penetration depth ‫ס‬ 600 m) underneath a thin Cr 2 O 3 scale.…”

Section: Introductionmentioning

confidence: 99%

Internal corrosion of engineering alloys: Experiment and computer simulation

Krupp

Christ

2005

J Phs Eqil and Diff

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High-temperature corrosion is generally known as a material degradation process that occurs at the surface of engineering components. In the case of internal corrosion, the corrosive species penetrates into the material by solid-state diffusion leading to the formation of internal precipitates, for instance, oxides (internal oxidation), nitrides (internal nitridation), and carbides (carburization). It is known from numerous publications and technical failure cases that internal corrosion results in a strong deterioration of the properties of a material (i.e., near-surface embrittlement or the dissolution of strengthening phases). The present article introduces the classic theory of internal oxidation and reviews some recent research on internal corrosion phenomena that are closely related to the failure mechanisms of thermally grown protective oxide scales on several commercial high-temperature alloys (e.g., single-crystalline and polycrystalline Ni-base alloys and Cr steels). The mechanisms and kinetics of internal corrosion processes are determined by the temperature, the local chemical composition of the material, the solubility and diffusivity of the corrosive species, as well as the mechanical loading conditions. These influence factors are taken into account by means of a computer model combining a numerical finite-difference approach to solve the diffusion differential equations with the thermodynamic tool ChemApp. Using several examples, it is shown that the model has been applied successfully to simulate the internal nitridation, carburization, and oxidation of hightemperature alloys. Fig. 1 Internal oxidation and nitridation attack of a failed natural gas burner tube of alloy 601 operated at T ‫ס‬ 1100°C JPEDAV (2005) 26:487-493 Fig. 11 (a) Simulated Fe 3 O 4 concentration profile, and (b) comparison of experimentally determined and calculated inner-oxide scale thickness for exposure of the steel X60 to air at 550°C [20]

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“…The influence of thermodiffusion coatings of Pt-Co-A1 and Pt-A1 type on the cyclic strength of IN-738, U-700, IN-939 was discussed in [5,6].…”

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confidence: 99%

Cyclic strength of turbine blades made of cast nickel-based alloys

Troshchenko

Gryaznov

Malashenko³

et al. 2007

Strength Mater

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We study the cyclic strength and durability of service-exposed turbine blades made of and ÉP539LM nickel alloys, some of them with a protective coating, upon a long operating time in gas turbine compressor sets. The blades of alloy are found to have the highest cyclic strength. The cyclic strength of uncoated IN-738 blades is about 10% higher than that of coated blades.Subject of Research. The development of modern gas turbine engineering faces the ever increasing gas stream temperatures, densities, and velocities. Also, there is always a problem of contaminated air intake. All these factors affect the turbine lifetime. This in turn requires frequent preventive repairs which are quite expensive. Therefore, to increase lifetime and improve reliability of gas turbines is a task of great significance. Advances along this line are achieved owing to the development of new heat-resistant alloys and efficient anticorrosion coating processes to protect hot duct components, mainly blades and vanes, against the corrosive action of combustion products.Application of protective coatings on gas turbine airfoils is now a generally recognized way of increasing their durability and operating reliability. Conventional thermodiffusion coatings (aluminizing, alumosiliconizing, chromosiliconizing) turned out to be of little help because of the increase in gas flow temperatures, thermal stresses, specific loads, and were replaced by new heat-resistant materials. The repair of blades of gas turbine compressor sets (GTS), in particular MS-3002 or GTK-10I, involves, in addition to mechanical removal of all corrosion defects, the airfoil coating repair by argon-arc welding and high-temperature brazing.The blades for GTK-10I turbine compressor sets are usually made of IN-738. Recent trends in Ukraine are toward the use of ZMI-3U or ÉP539LM alloys which have similar physical-mechanical properties. It is known that multicomponent CoCrAlY or NiCoCrAlY protective coatings are applied on blade airfoils by electron beam physical vapor deposition [1, 2]. The advantage this process offers over the others is that elements with significantly different pressure (vapor tension) can be evaporated simultaneously from one and the same source at a melt temperature of 1500°C.After a blade foil has been coated, it is then subjected to a final heat treatment -aging at 845°C for 16-24 hunless an outer ceramic layer is applied on it. In the case of protective cermet coating, the blades are put through an aging process after the deposition of a strengthening ceramic layer up to 90 μm in thickness. For uncooled GTS blades the ceramic layer serves primarily for erosion and corrosion protection of the inner corrosion-resistant binding MCrALV coating by preventing its direct contact with combustion products. The strengthening ceramic coating improves the durability of blades of GTS turboprop engines. 0039-2316/07/3902-0109

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The Interaction of High Temperature Corrosion and Mechanical Properties of Alloys

Cited by 8 publications

References 4 publications

Analysis of Cracked Gas Turbine Blades

Analysis of Cracked Gas Turbine Blades

Internal corrosion of engineering alloys: Experiment and computer simulation

Cyclic strength of turbine blades made of cast nickel-based alloys

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