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SUPERVISOR
Morteza Shamanian esfahani
مرتضي شمعانيان اصفهاني (استاد راهنما)
 
STUDENT
Mohammadamir Derakhshi
محمدامير درخشي

FACULTY - DEPARTMENT

دانشکده مهندسی مواد
DEGREE
Master of Science (MSc)
YEAR
1398

TITLE

Assessment on Properties of Dissimilar Welds between Inconel 617 SuperAlloy and 310 Austenitic Stainless Steel by Electron beam Welding Method
The aim of this research was to analyze the relationship between the microstructure and mechanical or chemical properties of Inconel 617/AISI 310 stainless steel electron beam welds. The microstructure of the weldments was studied using scanning electron microscopy and the electron backscatter diffraction (EBSD) technique. Mechanical properties of the weldments, including tensile behavior, hardness and impact toughness resistance, were evaluated. The results indicated that the electron beam welding process led to the segregation of elements in the weld metals, and the formation of secondary phases rich in Co, Nb and Mo was reported too. EBSD studies also showed that the grains of the weldment had a variety of orientations. Also, the fraction of coincident-site lattice boundaries was non-uniformly distributed across the weldments. The tensile strength of the weldments was similar to that of the AISI 310 parent metal, and the tensile samples underwent the ductile fracture mode. Upon Charpy impact testing, the weldments underwent notch deformation and the ductile mode of fracture; however, the impact toughness resistance was lower, as compared with the base metals. Based on the performed tests, the heat input of 168 KJ/m could be recommended. The microstructure-corrosion beahvior results showed that the weld metals had weaker general corrosion resistance and pitting corrosion behavior than parent metals, as a result of the segregation of the elements and formation of the precipitates which were rich in Mo, Nb, Cr and Co. With increasing the welding travel speed, a finer dendritic microstructure was observed in weld metal, leading to the improvement of general corrosion resistance and localized corrosion behavior of the weld metal. The aim of this research was to analyze the relationship between the microstructure and mechanical or chemical properties of Inconel 617/AISI 310 stainless steel electron beam welds. The microstructure of the weldments was studied using scanning electron microscopy and the electron backscatter diffraction (EBSD) technique. Mechanical properties of the weldments, including tensile behavior, hardness and impact toughness resistance, were evaluated. The results indicated that the electron beam welding process led to the segregation of elements in the weld metals, and the formation of secondary phases rich in Co, Nb and Mo was reported too. EBSD studies also showed that the grains of the weldment had a variety of orientations. Also, the fraction of coincident-site lattice boundaries was non-uniformly distributed across the weldments. The tensile strength of the weldments was similar to that of the AISI 310 parent metal, and the tensile samples underwent the ductile fracture mode. Upon Charpy impact testing, the weldments underwent notch deformation and the ductile mode of fracture; however, the impact toughness resistance was lower, as compared with the base metals. Based on the performed tests, the heat input of 168 KJ/m could be recommended. The microstructure-corrosion beahvior results showed that the weld metals had weaker general corrosion resistance and pitting corrosion behavior than parent metals, as a result of the segregation of the elements and formation of the precipitates which were rich in Mo, Nb, Cr and Co. With increasing the welding travel speed, a finer dendritic microstructure was observed in weld metal, leading to the improvement of general corrosion resistance and localized corrosion behavior of the weld metal. Keywords: Inconel 617, AISI 310, microstructure, welding, High-energy beam, pitting corrosion Keywords: Inconel 617, AISI 310, microstructure, welding, High-energy beam, pitting corrosion
چکيده اتصال سوپرآلياژها به فولادهاي زنگ‌نزن از مباحثي است که اخيراً در تحقيقات بسياري ازمحققين مورد توجه قرار گرفته است. در پژوهش انجام شده، بررسي ومشخصه يابي بين ميکروساختاروخواص مکانيکي/شيميايي اتصال غيرمشابه فولادزنگ نزن آستنيتي 310 به سوپرآلياژاينکونل 617 توسط جوشکاري پرتوالکتروني پرداخته شده است.دراين پژوهش ابتداميکروساختاراتصال غيرمشابه توسط ميکروسکوپ نوري والکتروني مورد تجزيه وتحليل قرارگرفت، نتايج آزمون پراش الکتروني برگشتي حاکي ازآن است که جهت گيري دانه ها درناحيه جوشکاري متفاوت ازفلزات پايه مي باشد، ازطرفي نتايج آزمون طيف سنجي توزيع انرژي نشان مي دهد جدايش عناصرآلياژي نظيرکبالت، موليبدن ونئوبيوم باعث تشکيل فازهاي ثانويه درميکروساختارناحيه جوشکاري شده است. درادامه رفتارمکانيکي اتصالات صورت گرفته نظيراستحکام کششي، سختي وچقرمگي ضربه مورد مطالعه قرارگرفت، نتايج بررسي ها نشان مي دهند استحکام کششي ناحيه جوشکاري شده به فلزپايه فولاد زنگ نزن آستنيتي 310 نزديک تراست وازطرفي چقرمگي ضربه درناحيه جوشکاري شده درمقايسه با فلزات پايه ضعيف ترمي باشد، تصاويرشکست نمونه هاي مربوط به ارزيابي هاي مکانيکي حاکي ازشکست نرم درنمونه هاي جوشکاري شده دارند، لازم به ذکراست حرارت ورودي بهينه براي نمونه هاي جوشکاري شده 168 کيلوژول پيشنهاد مي شود. درنهايت رفتارخوردگي اتصال مذکوردراين پژوهش مورد بررسي ومطالعه قرارگرفت، نتايج بدست آمده نشان مي دهند جدايش عناصرآلياژي درناحيه جوشکاري شده باعث تشکيل يکسري فازهاي ثانويه مي شوند که اين شکل گيري باعث وخيم ترشدن مقاومت به خوردگي اتصالات مذکور بويژه مقاومت به خوردگي حفره اي دراين ناحيه مي شود که با افزايش سرعت جوشکاري و درنتيجه ميکروساختار ريزتراين عيب تا حدودي مرتفع مي شود. کلمات کليدي سوپرآلياژاينکونل617، فولاد زنگ نزن آستنيتي310، جوشکاري پرتوالکتروني، خوردگي حفره اي.

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