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Vijay K Singh - One of the best experts on this subject based on the ideXlab platform.
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effect of thermal aging on ductile brittle transition temperature of modified 9cr 1mo steel evaluated with reference temperature approach under Dynamic Loading Condition
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2013Co-Authors: S Sathyanarayanan, Joysurya Basu, A Moitra, G Sasikala, Vijay K SinghAbstract:The effect of thermal aging on the ductile-brittle transition behavior has been assessed for a modified 9Cr-1Mo steel (P91) using the reference temperature approach under Dynamic Loading Condition (T 0 dy ). The steel in normalized and tempered (NT) Condition and in different levels of subsequent cold work (CW) was subjected to thermal aging at temperatures of 873 K and 923 K (600 °C and 650 °C) for 5000 and 10,000 hours. For the NT and all the cold work Conditions of the starting material, a drastic increase in T 0 dy has been noticed after aging at 923 K (650 °C) for 10,000 h. A moderate increase was observed for the NT steel aged at 873 K (600 °C) for 5000 hours and for the 10 pct CW steel aged at 873 K (600 °C) for 10,000 h. A detailed transmission electron microscope (TEM) study of the embrittled materials aged at 923 K (650 °C)/10,000 hours and 873 K (600 °C)/10,000 hours has indicated presence of hexagonal Laves phase of Fe2(Mo,Nb) type with different size and spatial distributions. The increase in the T 0 dy is attributed to the embrittling effect of a network of Laves phase precipitates along the grain boundaries.
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evaluation of Dynamic fracture toughness based reference temperature t0dy of modified 9cr 1mo steel in phosphorus embrittled and cold worked Condition
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: S Sathyanarayanan, A Moitra, G Sasikala, K G Samuel, S K Ray, Vijay K SinghAbstract:Abstract In the present study, the DBTT of a high phosphorus bearing modified 9Cr–1Mo steel in normalized and tempered (N&T) Condition and also after 5% and 10% cold work, has been evaluated by extending the reference temperature ( T 0 ) based Master Curve approach to Dynamic Loading Conditions. The reference temperature in Dynamic Loading Condition ( T 0 dy ) thus determined is found to be significantly high for the N&T Mod.9Cr–1Mo steel as compared to plain 9Cr–1Mo steel. Cold-work effect was not found to be significant in T 0 dy evaluation of Mod.9Cr–1Mo steel. The high T 0 dy of the present Mod.9Cr–1Mo steel is attributed to a fracture initiation mechanism predominated by decohesion of prior austenitic grain boundaries at the fatigue pre-crack front. This is attributed to segregation of phosphorus along the prior austenitic grain boundaries causing embrittlement, supported by SEM and Secondary Ion Mass Spectrometry (SIMS) observations.
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Evaluation of Dynamic fracture toughness based reference temperature (T0dy) of modified 9Cr–1Mo steel in phosphorus embrittled and cold-worked Condition
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: S Sathyanarayanan, A Moitra, G Sasikala, K G Samuel, S K Ray, Vijay K SinghAbstract:Abstract In the present study, the DBTT of a high phosphorus bearing modified 9Cr–1Mo steel in normalized and tempered (N&T) Condition and also after 5% and 10% cold work, has been evaluated by extending the reference temperature ( T 0 ) based Master Curve approach to Dynamic Loading Conditions. The reference temperature in Dynamic Loading Condition ( T 0 dy ) thus determined is found to be significantly high for the N&T Mod.9Cr–1Mo steel as compared to plain 9Cr–1Mo steel. Cold-work effect was not found to be significant in T 0 dy evaluation of Mod.9Cr–1Mo steel. The high T 0 dy of the present Mod.9Cr–1Mo steel is attributed to a fracture initiation mechanism predominated by decohesion of prior austenitic grain boundaries at the fatigue pre-crack front. This is attributed to segregation of phosphorus along the prior austenitic grain boundaries causing embrittlement, supported by SEM and Secondary Ion Mass Spectrometry (SIMS) observations.
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ductile brittle transition temperatures and Dynamic fracture toughness of 9cr 1mo steel
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2005Co-Authors: A Moitra, P R Sreenivasan, S L Mannan, Vijay K SinghAbstract:The ductile-brittle transition temperature (DBTT) of 9Cr-1Mo steel was characterized by an RT NDT-based K IR curve approach and a reference temperature (T 0)-based master curve (MC) approach. The MC was developed at a Dynamic Loading Condition (Loading rate of 5.12 m/s), using precracked Charpy V-notch (PCVN) specimens, and the reference temperature was termed T 0 dy . The RT NDT and T 0 dy were determined to be −25 °C and −52 °C, respectively. The T 0 dy was also estimated from instrumented CVN tests, using a modified Schindler procedure to evaluate K Jd ; the result shows close agreement with that obtained from the PCVN tests. The ASME K IR -curve approach proves to be too conservative compared to the obtained trend of the fracture toughness with temperature. The cleavage fracture stress, σ* f , estimated from the critical length, l*, shows good agreement with that estimated from the load-temperature diagram (2400 to 2450 MPa), which was constructed from the CVN test results. The crack initiation mechanism has been identified as decohesion of the particle-matrix interface, rather than as the fracture of the particles.
S Sathyanarayanan - One of the best experts on this subject based on the ideXlab platform.
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a study of fracture mechanisms in rafm steel in the ductile to brittle transition temperature regime
Procedia Engineering, 2014Co-Authors: A Moitra, S Sathyanarayanan, G Sasikala, Arup Dasgupta, S K Albert, S Saroja, A K Bhaduri, Rajendra E Kumar, T JayakumarAbstract:Abstract The fracture behaviour of a Reduced Activation Ferritic Martensitic Steel (RAFM) has been studied within the Ductile to Brittle Transition Temperature (DBTT) regime. The DBTT has been determined by ASTM E 1921 based reference temperature approach under Dynamic Loading Condition. The Dynamic reference temperature (T0dy) was found to be − 33.8 °C. The fracture mechanism has been studied by extracting TEM specimens precisely at the crack initiation sites using focused ion beam (FIB) technique in a high resolution dual beam scanning electron microscope. Detailed analytical TEM studies revealed that the morphology of carbides play a crucial role in the initiation of a crack. The larger ellipsoidal carbides, which were found to be Cr-rich, have been found to be responsible for dislocation piles ups. The shorter edge of these ellipsoidal carbides are areas of high stress concentration and were found to initiate cracks by decohesion of the particle-matrix interface. On the contrary, the iron rich carbides have been found to be smaller, more spherical, and thus less effective in blocking dislocation movement and therefore formation of pile ups. The results, which reveal an important mechanism towards crack initiation in ferritic-martensitic steels, will be presented in detail.
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effect of thermal aging on ductile brittle transition temperature of modified 9cr 1mo steel evaluated with reference temperature approach under Dynamic Loading Condition
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2013Co-Authors: S Sathyanarayanan, Joysurya Basu, A Moitra, G Sasikala, Vijay K SinghAbstract:The effect of thermal aging on the ductile-brittle transition behavior has been assessed for a modified 9Cr-1Mo steel (P91) using the reference temperature approach under Dynamic Loading Condition (T 0 dy ). The steel in normalized and tempered (NT) Condition and in different levels of subsequent cold work (CW) was subjected to thermal aging at temperatures of 873 K and 923 K (600 °C and 650 °C) for 5000 and 10,000 hours. For the NT and all the cold work Conditions of the starting material, a drastic increase in T 0 dy has been noticed after aging at 923 K (650 °C) for 10,000 h. A moderate increase was observed for the NT steel aged at 873 K (600 °C) for 5000 hours and for the 10 pct CW steel aged at 873 K (600 °C) for 10,000 h. A detailed transmission electron microscope (TEM) study of the embrittled materials aged at 923 K (650 °C)/10,000 hours and 873 K (600 °C)/10,000 hours has indicated presence of hexagonal Laves phase of Fe2(Mo,Nb) type with different size and spatial distributions. The increase in the T 0 dy is attributed to the embrittling effect of a network of Laves phase precipitates along the grain boundaries.
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evaluation of Dynamic fracture toughness based reference temperature t0dy of modified 9cr 1mo steel in phosphorus embrittled and cold worked Condition
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: S Sathyanarayanan, A Moitra, G Sasikala, K G Samuel, S K Ray, Vijay K SinghAbstract:Abstract In the present study, the DBTT of a high phosphorus bearing modified 9Cr–1Mo steel in normalized and tempered (N&T) Condition and also after 5% and 10% cold work, has been evaluated by extending the reference temperature ( T 0 ) based Master Curve approach to Dynamic Loading Conditions. The reference temperature in Dynamic Loading Condition ( T 0 dy ) thus determined is found to be significantly high for the N&T Mod.9Cr–1Mo steel as compared to plain 9Cr–1Mo steel. Cold-work effect was not found to be significant in T 0 dy evaluation of Mod.9Cr–1Mo steel. The high T 0 dy of the present Mod.9Cr–1Mo steel is attributed to a fracture initiation mechanism predominated by decohesion of prior austenitic grain boundaries at the fatigue pre-crack front. This is attributed to segregation of phosphorus along the prior austenitic grain boundaries causing embrittlement, supported by SEM and Secondary Ion Mass Spectrometry (SIMS) observations.
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Evaluation of Dynamic fracture toughness based reference temperature (T0dy) of modified 9Cr–1Mo steel in phosphorus embrittled and cold-worked Condition
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: S Sathyanarayanan, A Moitra, G Sasikala, K G Samuel, S K Ray, Vijay K SinghAbstract:Abstract In the present study, the DBTT of a high phosphorus bearing modified 9Cr–1Mo steel in normalized and tempered (N&T) Condition and also after 5% and 10% cold work, has been evaluated by extending the reference temperature ( T 0 ) based Master Curve approach to Dynamic Loading Conditions. The reference temperature in Dynamic Loading Condition ( T 0 dy ) thus determined is found to be significantly high for the N&T Mod.9Cr–1Mo steel as compared to plain 9Cr–1Mo steel. Cold-work effect was not found to be significant in T 0 dy evaluation of Mod.9Cr–1Mo steel. The high T 0 dy of the present Mod.9Cr–1Mo steel is attributed to a fracture initiation mechanism predominated by decohesion of prior austenitic grain boundaries at the fatigue pre-crack front. This is attributed to segregation of phosphorus along the prior austenitic grain boundaries causing embrittlement, supported by SEM and Secondary Ion Mass Spectrometry (SIMS) observations.
A Moitra - One of the best experts on this subject based on the ideXlab platform.
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a study of fracture mechanisms in rafm steel in the ductile to brittle transition temperature regime
Procedia Engineering, 2014Co-Authors: A Moitra, S Sathyanarayanan, G Sasikala, Arup Dasgupta, S K Albert, S Saroja, A K Bhaduri, Rajendra E Kumar, T JayakumarAbstract:Abstract The fracture behaviour of a Reduced Activation Ferritic Martensitic Steel (RAFM) has been studied within the Ductile to Brittle Transition Temperature (DBTT) regime. The DBTT has been determined by ASTM E 1921 based reference temperature approach under Dynamic Loading Condition. The Dynamic reference temperature (T0dy) was found to be − 33.8 °C. The fracture mechanism has been studied by extracting TEM specimens precisely at the crack initiation sites using focused ion beam (FIB) technique in a high resolution dual beam scanning electron microscope. Detailed analytical TEM studies revealed that the morphology of carbides play a crucial role in the initiation of a crack. The larger ellipsoidal carbides, which were found to be Cr-rich, have been found to be responsible for dislocation piles ups. The shorter edge of these ellipsoidal carbides are areas of high stress concentration and were found to initiate cracks by decohesion of the particle-matrix interface. On the contrary, the iron rich carbides have been found to be smaller, more spherical, and thus less effective in blocking dislocation movement and therefore formation of pile ups. The results, which reveal an important mechanism towards crack initiation in ferritic-martensitic steels, will be presented in detail.
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effect of thermal aging on ductile brittle transition temperature of modified 9cr 1mo steel evaluated with reference temperature approach under Dynamic Loading Condition
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2013Co-Authors: S Sathyanarayanan, Joysurya Basu, A Moitra, G Sasikala, Vijay K SinghAbstract:The effect of thermal aging on the ductile-brittle transition behavior has been assessed for a modified 9Cr-1Mo steel (P91) using the reference temperature approach under Dynamic Loading Condition (T 0 dy ). The steel in normalized and tempered (NT) Condition and in different levels of subsequent cold work (CW) was subjected to thermal aging at temperatures of 873 K and 923 K (600 °C and 650 °C) for 5000 and 10,000 hours. For the NT and all the cold work Conditions of the starting material, a drastic increase in T 0 dy has been noticed after aging at 923 K (650 °C) for 10,000 h. A moderate increase was observed for the NT steel aged at 873 K (600 °C) for 5000 hours and for the 10 pct CW steel aged at 873 K (600 °C) for 10,000 h. A detailed transmission electron microscope (TEM) study of the embrittled materials aged at 923 K (650 °C)/10,000 hours and 873 K (600 °C)/10,000 hours has indicated presence of hexagonal Laves phase of Fe2(Mo,Nb) type with different size and spatial distributions. The increase in the T 0 dy is attributed to the embrittling effect of a network of Laves phase precipitates along the grain boundaries.
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evaluation of Dynamic fracture toughness based reference temperature t0dy of modified 9cr 1mo steel in phosphorus embrittled and cold worked Condition
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: S Sathyanarayanan, A Moitra, G Sasikala, K G Samuel, S K Ray, Vijay K SinghAbstract:Abstract In the present study, the DBTT of a high phosphorus bearing modified 9Cr–1Mo steel in normalized and tempered (N&T) Condition and also after 5% and 10% cold work, has been evaluated by extending the reference temperature ( T 0 ) based Master Curve approach to Dynamic Loading Conditions. The reference temperature in Dynamic Loading Condition ( T 0 dy ) thus determined is found to be significantly high for the N&T Mod.9Cr–1Mo steel as compared to plain 9Cr–1Mo steel. Cold-work effect was not found to be significant in T 0 dy evaluation of Mod.9Cr–1Mo steel. The high T 0 dy of the present Mod.9Cr–1Mo steel is attributed to a fracture initiation mechanism predominated by decohesion of prior austenitic grain boundaries at the fatigue pre-crack front. This is attributed to segregation of phosphorus along the prior austenitic grain boundaries causing embrittlement, supported by SEM and Secondary Ion Mass Spectrometry (SIMS) observations.
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Evaluation of Dynamic fracture toughness based reference temperature (T0dy) of modified 9Cr–1Mo steel in phosphorus embrittled and cold-worked Condition
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: S Sathyanarayanan, A Moitra, G Sasikala, K G Samuel, S K Ray, Vijay K SinghAbstract:Abstract In the present study, the DBTT of a high phosphorus bearing modified 9Cr–1Mo steel in normalized and tempered (N&T) Condition and also after 5% and 10% cold work, has been evaluated by extending the reference temperature ( T 0 ) based Master Curve approach to Dynamic Loading Conditions. The reference temperature in Dynamic Loading Condition ( T 0 dy ) thus determined is found to be significantly high for the N&T Mod.9Cr–1Mo steel as compared to plain 9Cr–1Mo steel. Cold-work effect was not found to be significant in T 0 dy evaluation of Mod.9Cr–1Mo steel. The high T 0 dy of the present Mod.9Cr–1Mo steel is attributed to a fracture initiation mechanism predominated by decohesion of prior austenitic grain boundaries at the fatigue pre-crack front. This is attributed to segregation of phosphorus along the prior austenitic grain boundaries causing embrittlement, supported by SEM and Secondary Ion Mass Spectrometry (SIMS) observations.
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ductile brittle transition temperatures and Dynamic fracture toughness of 9cr 1mo steel
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2005Co-Authors: A Moitra, P R Sreenivasan, S L Mannan, Vijay K SinghAbstract:The ductile-brittle transition temperature (DBTT) of 9Cr-1Mo steel was characterized by an RT NDT-based K IR curve approach and a reference temperature (T 0)-based master curve (MC) approach. The MC was developed at a Dynamic Loading Condition (Loading rate of 5.12 m/s), using precracked Charpy V-notch (PCVN) specimens, and the reference temperature was termed T 0 dy . The RT NDT and T 0 dy were determined to be −25 °C and −52 °C, respectively. The T 0 dy was also estimated from instrumented CVN tests, using a modified Schindler procedure to evaluate K Jd ; the result shows close agreement with that obtained from the PCVN tests. The ASME K IR -curve approach proves to be too conservative compared to the obtained trend of the fracture toughness with temperature. The cleavage fracture stress, σ* f , estimated from the critical length, l*, shows good agreement with that estimated from the load-temperature diagram (2400 to 2450 MPa), which was constructed from the CVN test results. The crack initiation mechanism has been identified as decohesion of the particle-matrix interface, rather than as the fracture of the particles.
G Sasikala - One of the best experts on this subject based on the ideXlab platform.
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a study of fracture mechanisms in rafm steel in the ductile to brittle transition temperature regime
Procedia Engineering, 2014Co-Authors: A Moitra, S Sathyanarayanan, G Sasikala, Arup Dasgupta, S K Albert, S Saroja, A K Bhaduri, Rajendra E Kumar, T JayakumarAbstract:Abstract The fracture behaviour of a Reduced Activation Ferritic Martensitic Steel (RAFM) has been studied within the Ductile to Brittle Transition Temperature (DBTT) regime. The DBTT has been determined by ASTM E 1921 based reference temperature approach under Dynamic Loading Condition. The Dynamic reference temperature (T0dy) was found to be − 33.8 °C. The fracture mechanism has been studied by extracting TEM specimens precisely at the crack initiation sites using focused ion beam (FIB) technique in a high resolution dual beam scanning electron microscope. Detailed analytical TEM studies revealed that the morphology of carbides play a crucial role in the initiation of a crack. The larger ellipsoidal carbides, which were found to be Cr-rich, have been found to be responsible for dislocation piles ups. The shorter edge of these ellipsoidal carbides are areas of high stress concentration and were found to initiate cracks by decohesion of the particle-matrix interface. On the contrary, the iron rich carbides have been found to be smaller, more spherical, and thus less effective in blocking dislocation movement and therefore formation of pile ups. The results, which reveal an important mechanism towards crack initiation in ferritic-martensitic steels, will be presented in detail.
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effect of thermal aging on ductile brittle transition temperature of modified 9cr 1mo steel evaluated with reference temperature approach under Dynamic Loading Condition
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2013Co-Authors: S Sathyanarayanan, Joysurya Basu, A Moitra, G Sasikala, Vijay K SinghAbstract:The effect of thermal aging on the ductile-brittle transition behavior has been assessed for a modified 9Cr-1Mo steel (P91) using the reference temperature approach under Dynamic Loading Condition (T 0 dy ). The steel in normalized and tempered (NT) Condition and in different levels of subsequent cold work (CW) was subjected to thermal aging at temperatures of 873 K and 923 K (600 °C and 650 °C) for 5000 and 10,000 hours. For the NT and all the cold work Conditions of the starting material, a drastic increase in T 0 dy has been noticed after aging at 923 K (650 °C) for 10,000 h. A moderate increase was observed for the NT steel aged at 873 K (600 °C) for 5000 hours and for the 10 pct CW steel aged at 873 K (600 °C) for 10,000 h. A detailed transmission electron microscope (TEM) study of the embrittled materials aged at 923 K (650 °C)/10,000 hours and 873 K (600 °C)/10,000 hours has indicated presence of hexagonal Laves phase of Fe2(Mo,Nb) type with different size and spatial distributions. The increase in the T 0 dy is attributed to the embrittling effect of a network of Laves phase precipitates along the grain boundaries.
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evaluation of Dynamic fracture toughness based reference temperature t0dy of modified 9cr 1mo steel in phosphorus embrittled and cold worked Condition
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: S Sathyanarayanan, A Moitra, G Sasikala, K G Samuel, S K Ray, Vijay K SinghAbstract:Abstract In the present study, the DBTT of a high phosphorus bearing modified 9Cr–1Mo steel in normalized and tempered (N&T) Condition and also after 5% and 10% cold work, has been evaluated by extending the reference temperature ( T 0 ) based Master Curve approach to Dynamic Loading Conditions. The reference temperature in Dynamic Loading Condition ( T 0 dy ) thus determined is found to be significantly high for the N&T Mod.9Cr–1Mo steel as compared to plain 9Cr–1Mo steel. Cold-work effect was not found to be significant in T 0 dy evaluation of Mod.9Cr–1Mo steel. The high T 0 dy of the present Mod.9Cr–1Mo steel is attributed to a fracture initiation mechanism predominated by decohesion of prior austenitic grain boundaries at the fatigue pre-crack front. This is attributed to segregation of phosphorus along the prior austenitic grain boundaries causing embrittlement, supported by SEM and Secondary Ion Mass Spectrometry (SIMS) observations.
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Evaluation of Dynamic fracture toughness based reference temperature (T0dy) of modified 9Cr–1Mo steel in phosphorus embrittled and cold-worked Condition
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: S Sathyanarayanan, A Moitra, G Sasikala, K G Samuel, S K Ray, Vijay K SinghAbstract:Abstract In the present study, the DBTT of a high phosphorus bearing modified 9Cr–1Mo steel in normalized and tempered (N&T) Condition and also after 5% and 10% cold work, has been evaluated by extending the reference temperature ( T 0 ) based Master Curve approach to Dynamic Loading Conditions. The reference temperature in Dynamic Loading Condition ( T 0 dy ) thus determined is found to be significantly high for the N&T Mod.9Cr–1Mo steel as compared to plain 9Cr–1Mo steel. Cold-work effect was not found to be significant in T 0 dy evaluation of Mod.9Cr–1Mo steel. The high T 0 dy of the present Mod.9Cr–1Mo steel is attributed to a fracture initiation mechanism predominated by decohesion of prior austenitic grain boundaries at the fatigue pre-crack front. This is attributed to segregation of phosphorus along the prior austenitic grain boundaries causing embrittlement, supported by SEM and Secondary Ion Mass Spectrometry (SIMS) observations.
K G Samuel - One of the best experts on this subject based on the ideXlab platform.
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evaluation of Dynamic fracture toughness based reference temperature t0dy of modified 9cr 1mo steel in phosphorus embrittled and cold worked Condition
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: S Sathyanarayanan, A Moitra, G Sasikala, K G Samuel, S K Ray, Vijay K SinghAbstract:Abstract In the present study, the DBTT of a high phosphorus bearing modified 9Cr–1Mo steel in normalized and tempered (N&T) Condition and also after 5% and 10% cold work, has been evaluated by extending the reference temperature ( T 0 ) based Master Curve approach to Dynamic Loading Conditions. The reference temperature in Dynamic Loading Condition ( T 0 dy ) thus determined is found to be significantly high for the N&T Mod.9Cr–1Mo steel as compared to plain 9Cr–1Mo steel. Cold-work effect was not found to be significant in T 0 dy evaluation of Mod.9Cr–1Mo steel. The high T 0 dy of the present Mod.9Cr–1Mo steel is attributed to a fracture initiation mechanism predominated by decohesion of prior austenitic grain boundaries at the fatigue pre-crack front. This is attributed to segregation of phosphorus along the prior austenitic grain boundaries causing embrittlement, supported by SEM and Secondary Ion Mass Spectrometry (SIMS) observations.
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Evaluation of Dynamic fracture toughness based reference temperature (T0dy) of modified 9Cr–1Mo steel in phosphorus embrittled and cold-worked Condition
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: S Sathyanarayanan, A Moitra, G Sasikala, K G Samuel, S K Ray, Vijay K SinghAbstract:Abstract In the present study, the DBTT of a high phosphorus bearing modified 9Cr–1Mo steel in normalized and tempered (N&T) Condition and also after 5% and 10% cold work, has been evaluated by extending the reference temperature ( T 0 ) based Master Curve approach to Dynamic Loading Conditions. The reference temperature in Dynamic Loading Condition ( T 0 dy ) thus determined is found to be significantly high for the N&T Mod.9Cr–1Mo steel as compared to plain 9Cr–1Mo steel. Cold-work effect was not found to be significant in T 0 dy evaluation of Mod.9Cr–1Mo steel. The high T 0 dy of the present Mod.9Cr–1Mo steel is attributed to a fracture initiation mechanism predominated by decohesion of prior austenitic grain boundaries at the fatigue pre-crack front. This is attributed to segregation of phosphorus along the prior austenitic grain boundaries causing embrittlement, supported by SEM and Secondary Ion Mass Spectrometry (SIMS) observations.
