The Experts below are selected from a list of 93 Experts worldwide ranked by ideXlab platform
R N Ghosh - One of the best experts on this subject based on the ideXlab platform.
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structure property correlation study of a service exposed first stage turbine blade in a power plant
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: Ashok K Ray, S R Singh, P K Roy, J Swaminathan, Y N Tiwari, S C Bose, R N GhoshAbstract:Abstract This paper deals with assessment of high temperature force controlled fatigue and creep properties of as received and 31,325 engine operating hours service exposed first row gas turbine blade in a power plant. The mechanical properties were evaluated from various regions, namely root portion (bottom portion), middle region or the airfoil region and the top region of the blade. The root portion showed superior fatigue and creep properties compared to the aerofoil region of the blade where the temperature distribution is maximum and the top or tip region, which is considerably narrow and brittle. The microstructural assessment of as received service exposed gas turbine blade of first row of gas turbine have been interpreted, which is required for developing process and technology for rejuvenation of turbine blades. The mechanical properties of each region were correlated with its corresponding microstructural characteristics. The blade is made of nickel base superalloy Udimet-520. Significant coarsening of γ′ precipitates in hot zones, e.g., root and mid-sections, as compared to the base microstructure of below platform region was observed. The coarsening occurred in the aerofoil region and was maximum in the top region of the blade. The originally thin and nearly continuous distribution of Grain Boundary Carbide precipitates became discontinuous with little increase in size in the root section whereas it changed to thick continuous precipitation enveloped by γ′ phase in mid-section. Grain Boundary cavitations are not observed. In addition, the usual distribution of intragranular MC Carbide precipitates in below platform section is nearly dissolved in mid-section while smaller size is observed in bottom or root section. But the blocky MC precipitates at Grain boundaries or close to Grain boundaries are degenerated into needle shaped sigma phase in the mid- and top sections. Formation of intragranular Cr-rich sigma phase is also observed in root, airfoil and top sections but their frequency of occurrence is more in mid- and top sections than the root section. The appearance of sigma phase also signals for the rejuvenation. All the Grain boundaries in mid- and top section show enveloping of M 23 C 6 Grain Boundary precipitates with γ′ phase, because of following transformation at Grain boundaries: MC + γ ⇒ M 23 C 6 + γ′ (γ′ envelopes the M 23 C 6 ). The remnant coating at root section is 100–120 μm. In mid-section it is about 10 μm with base metal attack down to 20 μm. In addition, the width of TCP phase formation zone in subsurface region of base metal is about 200 μm in mid-section while it is about 100 μm in root section. Compared to the root and below platform sections of the virgin material the service exposed blade revealed MC intragranular precipitation in below platform, dissolution of intragranular MC precipitates and coarsening of Grain Boundary precipitates in the root section respectively.
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fatigue and creep damage and its correlation with microstructure of a service exposed first stage turbine blade in a power plant
Journal of Metallurgy and Materials Science, 2005Co-Authors: Ashok K Ray, S R Singh, Ansu J Kailath, P K Roy, Swapan K Das, R N GhoshAbstract:This paper deals with assessment of high temperature load controlled fatigue and creep properties of as received and 31,325 engine operating hours service exposed first row gas turbine blade in a power plant. High temperature fatigue and accelerated creep properties were evaluated from various regions, namely root portion (bottom portion), middle region or the airfoil region and the top region of the blade. The root portion showed superior fatigue and creep properties compared to the aerofoil region of the blade where the temperature distribution is maximum and the top or tip region which is considerably narrow and brittle. The microstructural assessment of as received service exposed gas turbine blade of first row of gas turbine have been interpreted, which is required for developing process & technology for rejuvenation of turbine blades. The mechanical properties of each region were correlated with its corresponding microstructural characteristics. The blade is made of nickel base superalloy Udimet-520. Significant coarsening of γ' precipitates in hot zones, e.g., root and mid sections, as compared to the base microstructure of below platform region was observed. The coarsening occurred in the aerofoil region and was maximum in the top region of the blade. The original thin and nearly continuous distribution of Grain Boundary Carbide precipitates became discontinuous with little increase in size in the root section whereas it changed to thick continuous precipitation enveloped by γ' phase in mid section. Grain Boundary cavitations are not observed. Therefore, Hipping is not essential for rejuvenation. In addition, the usual distribution of intragranular MC Carbide precipitates in below platform section is nearly dissolved in mid section while smaller size is observed in bottom or root section. But the blocky MC precipitates at Grain boundaries or close to Grain boundaries are degenerated into needle shaped sigma phase in the mid and top sections. Formation of intragranular Cr-rich sigma phase is also observed in root, airfoil and top sections but their frequency of occurrence is more in mid&top sections than the root section. The appearance of sigma phase also signals for the rejuvenation. All the Grain boundaries in mid section and top section show enveloping of M23C6 Grain Boundary precipitates with γ' phase, because of following transformation at Grain boundaries: MC + γ ⇒ M23C6 + γ′(γ′ envelopes the M23C6). The remnant coating at root section is 100–120 mm. In mid section it is about 10 μm with base metal attack down to 20 μm. In addition, the width of TCP phase formation zone in subsurface region of base metal is about 200 m in mid section while it is about 100 μm in root section.
Ashok K Ray - One of the best experts on this subject based on the ideXlab platform.
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structure property correlation study of a service exposed first stage turbine blade in a power plant
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: Ashok K Ray, S R Singh, P K Roy, J Swaminathan, Y N Tiwari, S C Bose, R N GhoshAbstract:Abstract This paper deals with assessment of high temperature force controlled fatigue and creep properties of as received and 31,325 engine operating hours service exposed first row gas turbine blade in a power plant. The mechanical properties were evaluated from various regions, namely root portion (bottom portion), middle region or the airfoil region and the top region of the blade. The root portion showed superior fatigue and creep properties compared to the aerofoil region of the blade where the temperature distribution is maximum and the top or tip region, which is considerably narrow and brittle. The microstructural assessment of as received service exposed gas turbine blade of first row of gas turbine have been interpreted, which is required for developing process and technology for rejuvenation of turbine blades. The mechanical properties of each region were correlated with its corresponding microstructural characteristics. The blade is made of nickel base superalloy Udimet-520. Significant coarsening of γ′ precipitates in hot zones, e.g., root and mid-sections, as compared to the base microstructure of below platform region was observed. The coarsening occurred in the aerofoil region and was maximum in the top region of the blade. The originally thin and nearly continuous distribution of Grain Boundary Carbide precipitates became discontinuous with little increase in size in the root section whereas it changed to thick continuous precipitation enveloped by γ′ phase in mid-section. Grain Boundary cavitations are not observed. In addition, the usual distribution of intragranular MC Carbide precipitates in below platform section is nearly dissolved in mid-section while smaller size is observed in bottom or root section. But the blocky MC precipitates at Grain boundaries or close to Grain boundaries are degenerated into needle shaped sigma phase in the mid- and top sections. Formation of intragranular Cr-rich sigma phase is also observed in root, airfoil and top sections but their frequency of occurrence is more in mid- and top sections than the root section. The appearance of sigma phase also signals for the rejuvenation. All the Grain boundaries in mid- and top section show enveloping of M 23 C 6 Grain Boundary precipitates with γ′ phase, because of following transformation at Grain boundaries: MC + γ ⇒ M 23 C 6 + γ′ (γ′ envelopes the M 23 C 6 ). The remnant coating at root section is 100–120 μm. In mid-section it is about 10 μm with base metal attack down to 20 μm. In addition, the width of TCP phase formation zone in subsurface region of base metal is about 200 μm in mid-section while it is about 100 μm in root section. Compared to the root and below platform sections of the virgin material the service exposed blade revealed MC intragranular precipitation in below platform, dissolution of intragranular MC precipitates and coarsening of Grain Boundary precipitates in the root section respectively.
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fatigue and creep damage and its correlation with microstructure of a service exposed first stage turbine blade in a power plant
Journal of Metallurgy and Materials Science, 2005Co-Authors: Ashok K Ray, S R Singh, Ansu J Kailath, P K Roy, Swapan K Das, R N GhoshAbstract:This paper deals with assessment of high temperature load controlled fatigue and creep properties of as received and 31,325 engine operating hours service exposed first row gas turbine blade in a power plant. High temperature fatigue and accelerated creep properties were evaluated from various regions, namely root portion (bottom portion), middle region or the airfoil region and the top region of the blade. The root portion showed superior fatigue and creep properties compared to the aerofoil region of the blade where the temperature distribution is maximum and the top or tip region which is considerably narrow and brittle. The microstructural assessment of as received service exposed gas turbine blade of first row of gas turbine have been interpreted, which is required for developing process & technology for rejuvenation of turbine blades. The mechanical properties of each region were correlated with its corresponding microstructural characteristics. The blade is made of nickel base superalloy Udimet-520. Significant coarsening of γ' precipitates in hot zones, e.g., root and mid sections, as compared to the base microstructure of below platform region was observed. The coarsening occurred in the aerofoil region and was maximum in the top region of the blade. The original thin and nearly continuous distribution of Grain Boundary Carbide precipitates became discontinuous with little increase in size in the root section whereas it changed to thick continuous precipitation enveloped by γ' phase in mid section. Grain Boundary cavitations are not observed. Therefore, Hipping is not essential for rejuvenation. In addition, the usual distribution of intragranular MC Carbide precipitates in below platform section is nearly dissolved in mid section while smaller size is observed in bottom or root section. But the blocky MC precipitates at Grain boundaries or close to Grain boundaries are degenerated into needle shaped sigma phase in the mid and top sections. Formation of intragranular Cr-rich sigma phase is also observed in root, airfoil and top sections but their frequency of occurrence is more in mid&top sections than the root section. The appearance of sigma phase also signals for the rejuvenation. All the Grain boundaries in mid section and top section show enveloping of M23C6 Grain Boundary precipitates with γ' phase, because of following transformation at Grain boundaries: MC + γ ⇒ M23C6 + γ′(γ′ envelopes the M23C6). The remnant coating at root section is 100–120 mm. In mid section it is about 10 μm with base metal attack down to 20 μm. In addition, the width of TCP phase formation zone in subsurface region of base metal is about 200 m in mid section while it is about 100 μm in root section.
Takeshi Kuwana - One of the best experts on this subject based on the ideXlab platform.
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dependence of Carbide precipitation on Grain Boundary structure in sensitized austenitic stainless steel
2000Co-Authors: Hiroyuki Kokawa, M Shimada, Yutaka S Sato, Takashi Koyanagawa, Takeshi KuwanaAbstract:Grain Boundary Carbide precipitation and intergranular corrosion in sensitized austenite stainless steel were examined by transmission electron microscopy (TEM) to clarify the effect of Grain Boundary structure on precipitation and corrosion. A type 304 steel, which had been solutionized at 1350 K was heat-treated at temperatures of 800-1300 K. Oxalic acid etch and Strauss tests showed that the frequency of Grain boundaries with M23C6 Carbide precipitation and corroded boundaries increased with holding time at sensitizing temperatures. The Grain Boundary Carbide precipitation was observed during heat treatment at 1000 K by TEM. Grain boundaries were characterized on the basis of the Coincidence Site Lattice (CSL) theory using electron diffraction Kikuchi patterns. The observations revealed that the propensity to intergranular precipitation depends strongly on the Grain Boundary structure. Carbide precipitates tend to be detected at Grain boundaries with higher Σ -values or larger deviation angles (Δθ) from low- Σ CSL misorientations. The border lines between precipitation and no precipitation can be drawn by a deviation parameter of Δθ/ΔθC, where Δθc is the maximum deviation angle by Brandon’s criterion. The border line of Δθ/Δθc decreased with the increase in the holding time at 1000 K. This means that the more ordered Boundary needs the longer time for intergranular Carbide precipitation and corrosion than less ordered or random boundaries.
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effect of Grain Boundary structure on weld decay of austenitic stainless steel part 2 Grain Boundary structure and Carbide precipitation in type 304 stainless steel weld heat affected zone
Quarterly Journal of The Japan Welding Society, 1991Co-Authors: Hiroyuki Kokawa, Takeshi KuwanaAbstract:Grain Boundary Carbide precipitation in weld heat affected zone of type 304 and 304L, austenitic stainless steels was observed using transmission electron microscope to make clear the effects of Grain Boundary misorientation and structure on Carbide precipitation at Grain boundaries in stainless steel welds from a crystallographic viewpoint. Grain Boundary Carbides were detected in Grain Boundary precipitation region of the 304 steel weld heat affected zone. In that region, some Grain boundaries had Carbide precipitates, but some were precipitation-free. Kikuchi line analyses showed that Grain boundaries with ordered atomic structures had no Carbide precipitates. This tendency was valid in 304L steel weld, although Grain Boundary Carbide precipitates were finer in 304L, steel than in 304 steel. These facts have suggested that Grain Boundary precipitation and corrosion in stainless steel weld heat affected zone depend sensitively on crystallographic character of Grain Boundary.
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effect of Grain Boundary structure on weld decay of austenitic stainless steel part 3 Grain Boundary structure and Carbide precipitation in a type 304 stainless steel at high temperatures
Quarterly Journal of The Japan Welding Society, 1991Co-Authors: Hiroyuki Kokawa, Takashi Koyanagawa, Takeshi KuwanaAbstract:A type 304 austenitic stainless steel was heat-treated at temperatures of 800-1300 K, and the heat-treated specimens were observed by optical and transmission electron microscopy to examine the effect of crystallographic character of Grain Boundary on Carbide precipitation and corrosion.At sensitizing temperatures, Grain boundaries with Carbide precipitation or corroded boundaries increased with holding time. Kikuchi line analyses showed that Grain Boundary Carbide precipitation and corrosion sensitively depended on the Grain Boundary structure. A more ordered Boundary needed longer time for Carbide precipitation or corrosion than a less ordered Boundary. This fact suggests that weld decay in austenitic stainless steel can be prevented by increasing the percentage of ordered boundaries in the material.
Hiroyuki Kokawa - One of the best experts on this subject based on the ideXlab platform.
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Grain Boundary structure and precipitation in sensitized austenitic stainless steel
JOM, 2000Co-Authors: Hiroyuki Kokawa, M Shimada, Yutaka S SatoAbstract:Grain-Boundary Carbide precipitation and intergranular corrosion in sensitized austenite stainless steel were examined by transmission electron microscopy to clarify the effect of Grain-Boundary structure on precipitation and corrosion. The propensity to intergranular precipitation depends strongly on the Grain-Boundary structure. Carbide precipitates tend to be detected at Grain boundaries with higher Σ values or larger deviation angles (Δθ) from low-Σ coincidence site lattice misorientations. The more ordered Boundary requires a longer time for intergranular Carbide precipitation and corrosion than less ordered or random boundaries.
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dependence of Carbide precipitation on Grain Boundary structure in sensitized austenitic stainless steel
2000Co-Authors: Hiroyuki Kokawa, M Shimada, Yutaka S Sato, Takashi Koyanagawa, Takeshi KuwanaAbstract:Grain Boundary Carbide precipitation and intergranular corrosion in sensitized austenite stainless steel were examined by transmission electron microscopy (TEM) to clarify the effect of Grain Boundary structure on precipitation and corrosion. A type 304 steel, which had been solutionized at 1350 K was heat-treated at temperatures of 800-1300 K. Oxalic acid etch and Strauss tests showed that the frequency of Grain boundaries with M23C6 Carbide precipitation and corroded boundaries increased with holding time at sensitizing temperatures. The Grain Boundary Carbide precipitation was observed during heat treatment at 1000 K by TEM. Grain boundaries were characterized on the basis of the Coincidence Site Lattice (CSL) theory using electron diffraction Kikuchi patterns. The observations revealed that the propensity to intergranular precipitation depends strongly on the Grain Boundary structure. Carbide precipitates tend to be detected at Grain boundaries with higher Σ -values or larger deviation angles (Δθ) from low- Σ CSL misorientations. The border lines between precipitation and no precipitation can be drawn by a deviation parameter of Δθ/ΔθC, where Δθc is the maximum deviation angle by Brandon’s criterion. The border line of Δθ/Δθc decreased with the increase in the holding time at 1000 K. This means that the more ordered Boundary needs the longer time for intergranular Carbide precipitation and corrosion than less ordered or random boundaries.
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effect of Grain Boundary structure on weld decay of austenitic stainless steel part 2 Grain Boundary structure and Carbide precipitation in type 304 stainless steel weld heat affected zone
Quarterly Journal of The Japan Welding Society, 1991Co-Authors: Hiroyuki Kokawa, Takeshi KuwanaAbstract:Grain Boundary Carbide precipitation in weld heat affected zone of type 304 and 304L, austenitic stainless steels was observed using transmission electron microscope to make clear the effects of Grain Boundary misorientation and structure on Carbide precipitation at Grain boundaries in stainless steel welds from a crystallographic viewpoint. Grain Boundary Carbides were detected in Grain Boundary precipitation region of the 304 steel weld heat affected zone. In that region, some Grain boundaries had Carbide precipitates, but some were precipitation-free. Kikuchi line analyses showed that Grain boundaries with ordered atomic structures had no Carbide precipitates. This tendency was valid in 304L steel weld, although Grain Boundary Carbide precipitates were finer in 304L, steel than in 304 steel. These facts have suggested that Grain Boundary precipitation and corrosion in stainless steel weld heat affected zone depend sensitively on crystallographic character of Grain Boundary.
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effect of Grain Boundary structure on weld decay of austenitic stainless steel part 3 Grain Boundary structure and Carbide precipitation in a type 304 stainless steel at high temperatures
Quarterly Journal of The Japan Welding Society, 1991Co-Authors: Hiroyuki Kokawa, Takashi Koyanagawa, Takeshi KuwanaAbstract:A type 304 austenitic stainless steel was heat-treated at temperatures of 800-1300 K, and the heat-treated specimens were observed by optical and transmission electron microscopy to examine the effect of crystallographic character of Grain Boundary on Carbide precipitation and corrosion.At sensitizing temperatures, Grain boundaries with Carbide precipitation or corroded boundaries increased with holding time. Kikuchi line analyses showed that Grain Boundary Carbide precipitation and corrosion sensitively depended on the Grain Boundary structure. A more ordered Boundary needed longer time for Carbide precipitation or corrosion than a less ordered Boundary. This fact suggests that weld decay in austenitic stainless steel can be prevented by increasing the percentage of ordered boundaries in the material.
S R Singh - One of the best experts on this subject based on the ideXlab platform.
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structure property correlation study of a service exposed first stage turbine blade in a power plant
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: Ashok K Ray, S R Singh, P K Roy, J Swaminathan, Y N Tiwari, S C Bose, R N GhoshAbstract:Abstract This paper deals with assessment of high temperature force controlled fatigue and creep properties of as received and 31,325 engine operating hours service exposed first row gas turbine blade in a power plant. The mechanical properties were evaluated from various regions, namely root portion (bottom portion), middle region or the airfoil region and the top region of the blade. The root portion showed superior fatigue and creep properties compared to the aerofoil region of the blade where the temperature distribution is maximum and the top or tip region, which is considerably narrow and brittle. The microstructural assessment of as received service exposed gas turbine blade of first row of gas turbine have been interpreted, which is required for developing process and technology for rejuvenation of turbine blades. The mechanical properties of each region were correlated with its corresponding microstructural characteristics. The blade is made of nickel base superalloy Udimet-520. Significant coarsening of γ′ precipitates in hot zones, e.g., root and mid-sections, as compared to the base microstructure of below platform region was observed. The coarsening occurred in the aerofoil region and was maximum in the top region of the blade. The originally thin and nearly continuous distribution of Grain Boundary Carbide precipitates became discontinuous with little increase in size in the root section whereas it changed to thick continuous precipitation enveloped by γ′ phase in mid-section. Grain Boundary cavitations are not observed. In addition, the usual distribution of intragranular MC Carbide precipitates in below platform section is nearly dissolved in mid-section while smaller size is observed in bottom or root section. But the blocky MC precipitates at Grain boundaries or close to Grain boundaries are degenerated into needle shaped sigma phase in the mid- and top sections. Formation of intragranular Cr-rich sigma phase is also observed in root, airfoil and top sections but their frequency of occurrence is more in mid- and top sections than the root section. The appearance of sigma phase also signals for the rejuvenation. All the Grain boundaries in mid- and top section show enveloping of M 23 C 6 Grain Boundary precipitates with γ′ phase, because of following transformation at Grain boundaries: MC + γ ⇒ M 23 C 6 + γ′ (γ′ envelopes the M 23 C 6 ). The remnant coating at root section is 100–120 μm. In mid-section it is about 10 μm with base metal attack down to 20 μm. In addition, the width of TCP phase formation zone in subsurface region of base metal is about 200 μm in mid-section while it is about 100 μm in root section. Compared to the root and below platform sections of the virgin material the service exposed blade revealed MC intragranular precipitation in below platform, dissolution of intragranular MC precipitates and coarsening of Grain Boundary precipitates in the root section respectively.
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fatigue and creep damage and its correlation with microstructure of a service exposed first stage turbine blade in a power plant
Journal of Metallurgy and Materials Science, 2005Co-Authors: Ashok K Ray, S R Singh, Ansu J Kailath, P K Roy, Swapan K Das, R N GhoshAbstract:This paper deals with assessment of high temperature load controlled fatigue and creep properties of as received and 31,325 engine operating hours service exposed first row gas turbine blade in a power plant. High temperature fatigue and accelerated creep properties were evaluated from various regions, namely root portion (bottom portion), middle region or the airfoil region and the top region of the blade. The root portion showed superior fatigue and creep properties compared to the aerofoil region of the blade where the temperature distribution is maximum and the top or tip region which is considerably narrow and brittle. The microstructural assessment of as received service exposed gas turbine blade of first row of gas turbine have been interpreted, which is required for developing process & technology for rejuvenation of turbine blades. The mechanical properties of each region were correlated with its corresponding microstructural characteristics. The blade is made of nickel base superalloy Udimet-520. Significant coarsening of γ' precipitates in hot zones, e.g., root and mid sections, as compared to the base microstructure of below platform region was observed. The coarsening occurred in the aerofoil region and was maximum in the top region of the blade. The original thin and nearly continuous distribution of Grain Boundary Carbide precipitates became discontinuous with little increase in size in the root section whereas it changed to thick continuous precipitation enveloped by γ' phase in mid section. Grain Boundary cavitations are not observed. Therefore, Hipping is not essential for rejuvenation. In addition, the usual distribution of intragranular MC Carbide precipitates in below platform section is nearly dissolved in mid section while smaller size is observed in bottom or root section. But the blocky MC precipitates at Grain boundaries or close to Grain boundaries are degenerated into needle shaped sigma phase in the mid and top sections. Formation of intragranular Cr-rich sigma phase is also observed in root, airfoil and top sections but their frequency of occurrence is more in mid&top sections than the root section. The appearance of sigma phase also signals for the rejuvenation. All the Grain boundaries in mid section and top section show enveloping of M23C6 Grain Boundary precipitates with γ' phase, because of following transformation at Grain boundaries: MC + γ ⇒ M23C6 + γ′(γ′ envelopes the M23C6). The remnant coating at root section is 100–120 mm. In mid section it is about 10 μm with base metal attack down to 20 μm. In addition, the width of TCP phase formation zone in subsurface region of base metal is about 200 m in mid section while it is about 100 μm in root section.
