Creep behaviour determination and remaining life estimation for centrifucally cast tubes made of Nb-stabilised 25/35 Cr Ni iron-based superalloy
Savurma döküm yöntemiyle üretilmiş ve nb ile kararlı hale getirilmiş 25/35crni demir temelli üstünalaşımdan borularda sürünme davranışının ve kalan ömürün belirlenmesi
- Tez No: 56632
- Danışmanlar: PROF. DR. ERDOĞAN TEKİN
- Tez Türü: Doktora
- Konular: Metalurji Mühendisliği, Metallurgical Engineering
- Anahtar Kelimeler: Creep behavior of alloys, 9-projection method, remaining life estimation, iron-based superalloys, centrifugally cast superalloys. IV, Alaşımlar, Borular, Kullanım ömrü, Sürtünme, Creep behavior of alloys, 9-projection method, remaining life estimation, iron-based superalloys, centrifugally cast superalloys. IV, Alloys, Pipes, Remaining life, Friction
- Yıl: 1996
- Dil: İngilizce
- Üniversite: Orta Doğu Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Metalurji ve Malzeme Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: Belirtilmemiş.
Özet
ABSTRACT CREEP BEHAVIOR DETERMINATION AND REMAINING LIFE ESTIMATION FOR CENTRD7UGALLY CAST TUBES MADE OF Nb-STABILISED 25/35CrNi DAON-BASED SUPERALLOY ORHANER, Feyyaa Onder Ph.D, Department of Metallurgical and Materials Engineering Supervision Prof. Br. Erdoğan Tekin October 1996, 146 pages Tubes in the radiant sections of the naphta cracking furnaces where ethylene production is done, are mainly constructed using centrifugalfy cast tubes which are made of Nb-stabflised 25/35CrNi iron-based superalloys. Under service conditions tubes undergo creep due to their own weight and operating temperatures reaching 1100°C. Besides creep severe carburisation and oxidation take place on the tubes during service exposure. These severe conditions alter the mechanical behavior as well as the microstructure of the tubes during long-term service exposure. mIn this study, both microstructural and creep characterization of the as-cast and long-term-service-exposed tubes were determined. Microstructural examinations were carried out using optical and electronmetallographic, and x-ray techniques. 9- projection method based on constant stress creep tests were used to define the creep behavior of the alloy. Constant stress post-exposure creep tests were carried out to find out strain accumulation during long-term service exposure. The results in combination with 9-projection method were used to define the remaining life of the long-term-service-exposed tubes. Microstructural investigations showed that microstructure of the as-cast tubes is altered and a nonuniform microstructure through the thickness of the tubes develops during long-term service exposure. 9-projection method can be successfully used to define the creep behavior of the alloy. The results obtained under accelerated test conditions can successfiilfy be extrapolated to actual conditions. The remaining life estimation based on strain accumulation during long-term service exposure realistically defines the remnant life of the long-term-service-exposed tubes.
Özet (Çeviri)
ABSTRACT CREEP BEHAVIOR DETERMINATION AND REMAINING LIFE ESTIMATION FOR CENTRD7UGALLY CAST TUBES MADE OF Nb-STABILISED 25/35CrNi DAON-BASED SUPERALLOY ORHANER, Feyyaa Onder Ph.D, Department of Metallurgical and Materials Engineering Supervision Prof. Br. Erdoğan Tekin October 1996, 146 pages Tubes in the radiant sections of the naphta cracking furnaces where ethylene production is done, are mainly constructed using centrifugalfy cast tubes which are made of Nb-stabflised 25/35CrNi iron-based superalloys. Under service conditions tubes undergo creep due to their own weight and operating temperatures reaching 1100°C. Besides creep severe carburisation and oxidation take place on the tubes during service exposure. These severe conditions alter the mechanical behavior as well as the microstructure of the tubes during long-term service exposure. mIn this study, both microstructural and creep characterization of the as-cast and long-term-service-exposed tubes were determined. Microstructural examinations were carried out using optical and electronmetallographic, and x-ray techniques. 9- projection method based on constant stress creep tests were used to define the creep behavior of the alloy. Constant stress post-exposure creep tests were carried out to find out strain accumulation during long-term service exposure. The results in combination with 9-projection method were used to define the remaining life of the long-term-service-exposed tubes. Microstructural investigations showed that microstructure of the as-cast tubes is altered and a nonuniform microstructure through the thickness of the tubes develops during long-term service exposure. 9-projection method can be successfully used to define the creep behavior of the alloy. The results obtained under accelerated test conditions can successfiilfy be extrapolated to actual conditions. The remaining life estimation based on strain accumulation during long-term service exposure realistically defines the remnant life of the long-term-service-exposed tubes.
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