The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Masaki Nakajima - One of the best experts on this subject based on the ideXlab platform.
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Improvement of fatigue properties in type 304 stainless steel by annealing treatment in Nitrogen Gas
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014Co-Authors: Masayuki Akita, Yuki Nakamura, Toshifumi Kakiuchi, Yoshihiko Uematsu, Masaki NakajimaAbstract:Abstract The effects of annealing in Nitrogen Gas on the fatigue and static mechanical properties were studied using type 304 austenitic stainless steel. Annealing in Nitrogen Gas was performed at 1100 °C and at 1200 °C for 30 h, resulting in the precipitation of nitrides at grain boundaries and inside grains at both temperatures. The nitrides were identified as a chromium nitride by EDX analysis. There were fewer nitrides present in specimens treated at 1200 °C than at 1100 °C. The higher solubility of Nitrogen at 1200 °C lowered the amount of chromium nitride. The hardness and tensile tests revealed that the surface hardness and the static strength were significantly improved by annealing in Nitrogen Gas. The fatigue strengths of the annealed specimens significantly increased compared with that of the untreated specimen, and the specimen annealed at 1100 °C obtained a higher fatigue strength than that of the specimen annealed at 1200 °C. After fatigue tests at fatigue limit stress levels, a strain-induced martensitic transformation was observed in the untreated specimen because the austenite (γ) phase of type 304 steel is metastable. However, in the annealed specimens, the strain-induced martensitic transformation did not occur during fatigue tests at fatigue limit stress levels, indicating that γ was stabilized by Nitrogen in the solid solution.
Masayuki Akita - One of the best experts on this subject based on the ideXlab platform.
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Improvement of fatigue properties in type 304 stainless steel by annealing treatment in Nitrogen Gas
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014Co-Authors: Masayuki Akita, Yuki Nakamura, Toshifumi Kakiuchi, Yoshihiko Uematsu, Masaki NakajimaAbstract:Abstract The effects of annealing in Nitrogen Gas on the fatigue and static mechanical properties were studied using type 304 austenitic stainless steel. Annealing in Nitrogen Gas was performed at 1100 °C and at 1200 °C for 30 h, resulting in the precipitation of nitrides at grain boundaries and inside grains at both temperatures. The nitrides were identified as a chromium nitride by EDX analysis. There were fewer nitrides present in specimens treated at 1200 °C than at 1100 °C. The higher solubility of Nitrogen at 1200 °C lowered the amount of chromium nitride. The hardness and tensile tests revealed that the surface hardness and the static strength were significantly improved by annealing in Nitrogen Gas. The fatigue strengths of the annealed specimens significantly increased compared with that of the untreated specimen, and the specimen annealed at 1100 °C obtained a higher fatigue strength than that of the specimen annealed at 1200 °C. After fatigue tests at fatigue limit stress levels, a strain-induced martensitic transformation was observed in the untreated specimen because the austenite (γ) phase of type 304 steel is metastable. However, in the annealed specimens, the strain-induced martensitic transformation did not occur during fatigue tests at fatigue limit stress levels, indicating that γ was stabilized by Nitrogen in the solid solution.
Hadi Savaloni - One of the best experts on this subject based on the ideXlab platform.
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Influence of Nitrogen Gas Flow on Mechanical and Tribological Properties of Sputtered Chromium Nitride Thin Films
Advanced Materials Research, 2013Co-Authors: Morteza Jafarzadeh, K. Khojier, Hadi SavaloniAbstract:Nitride based hard coatings are widely used for mechanical applications. Among these coatings, chromium nitrides are especially interesting because of its good mechanical and tribological properties. In this work we have studied the influence of Nitrogen Gas flow on mechanical and tribological properties of chromium nitride thin films. The chromium nitride thin films were deposited on Al 5083 by DC magnetron sputtering technique at different Nitrogen Gas flows in the range of 5-20 sccm. Surface morphology and chemical composition of the films were studied using field emission scanning electron microscope (FESEM). The thickness of the films was determined by quartz crystal monitor and checked with FESEM cross-section images. The mechanical and tribological properties of the samples were investigated by means of nanoindentation and scratch tests. The results showed that films hardness increased with Nitrogen Gas flow, while coefficient of friction and scratch volume decreased. The structural investigations showed that these behaviors were due to the decrease of dislocation density and improvement of crystal quality.
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Influence of Nitrogen Gas Flow on Mechanical and Tribological Properties of Sputtered Chromium Nitride Thin Films
Advanced Materials Research, 2013Co-Authors: Morteza Jafarzadeh, K. Khojier, Hadi SavaloniAbstract:Nitride based hard coatings are widely used for mechanical applications. Among these coatings, chromium nitrides are especially interesting because of its good mechanical and tribological properties. In this work we have studied the influence of Nitrogen Gas flow on mechanical and tribological properties of chromium nitride thin films. The chromium nitride thin films were deposited on Al 5083 by DC magnetron sputtering technique at different Nitrogen Gas flows in the range of 5-20 sccm. Surface morphology and chemical composition of the films were studied using field emission scanning electron microscope (FESEM). The thickness of the films was determined by quartz crystal monitor and checked with FESEM cross-section images. The mechanical and tribological properties of the samples were investigated by means of nanoindentation and scratch tests. The results showed that films hardness increased with Nitrogen Gas flow, while coefficient of friction and scratch volume decreased. The structural investigations showed that these behaviors were due to the decrease of dislocation density and improvement of crystal quality.
Zin-hyoung Lee - One of the best experts on this subject based on the ideXlab platform.
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A method for predicting Nitrogen Gas pores in Nitrogen alloying stainless steels
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: Seong-ho Yang, Zin-hyoung LeeAbstract:A method for prediction of Nitrogen Gas pores in Nitrogen alloying stainless steels was proposed with combining experimental and calculated results. The critical Nitrogen content defined as maximum Nitrogen content without Nitrogen Gas pores was experimentally determined. The critical Nitrogen content was converted to the critical Nitrogen partial pressure with considering segregation of other alloying elements calculated by Thermo-Calc to predict the critical Nitrogen content with different Mn levels. The predicted critical Nitrogen content agreed favorably with experiments. This method can be used to predict the maximum amount of dissolved Nitrogen permissible in the melt in order to avoid the formation of Nitrogen Gas pores.
Yoshihiko Uematsu - One of the best experts on this subject based on the ideXlab platform.
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Improvement of fatigue properties in type 304 stainless steel by annealing treatment in Nitrogen Gas
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014Co-Authors: Masayuki Akita, Yuki Nakamura, Toshifumi Kakiuchi, Yoshihiko Uematsu, Masaki NakajimaAbstract:Abstract The effects of annealing in Nitrogen Gas on the fatigue and static mechanical properties were studied using type 304 austenitic stainless steel. Annealing in Nitrogen Gas was performed at 1100 °C and at 1200 °C for 30 h, resulting in the precipitation of nitrides at grain boundaries and inside grains at both temperatures. The nitrides were identified as a chromium nitride by EDX analysis. There were fewer nitrides present in specimens treated at 1200 °C than at 1100 °C. The higher solubility of Nitrogen at 1200 °C lowered the amount of chromium nitride. The hardness and tensile tests revealed that the surface hardness and the static strength were significantly improved by annealing in Nitrogen Gas. The fatigue strengths of the annealed specimens significantly increased compared with that of the untreated specimen, and the specimen annealed at 1100 °C obtained a higher fatigue strength than that of the specimen annealed at 1200 °C. After fatigue tests at fatigue limit stress levels, a strain-induced martensitic transformation was observed in the untreated specimen because the austenite (γ) phase of type 304 steel is metastable. However, in the annealed specimens, the strain-induced martensitic transformation did not occur during fatigue tests at fatigue limit stress levels, indicating that γ was stabilized by Nitrogen in the solid solution.