4885

4589

كارشناسي ارشد

خوردگي وحفاظت مواد

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مواد

1388

نه، 83ص: مصور، جدول، نمودار

ص.ع.به: فارسي و انگليسي

احمد ساعتچي، كيوان رئيسي

مرتضي شمعانيان

9/10/88

محمد علي گلعذار، ابراهيم حشمت دهكردي

مهندسي مواد

ID4589

به فارسي و انگليسي: قابل رويت در نسخه ديجيتال

Investigation of corrosion behavior of austenitic welded stainless steel Iman Berenjani imanberenjani@ma iut ac ir May 9 2009 Department of Materials Engineering Isfahan University of Technology 84156 83111 Isfahan IranDegree M Sc Language FarsiDr Ahmad Saatchi Prof Supervisor E mail asaatchi@cc iut ac irDr Keyvan Raeissi Assoc Prof Supervisor E mail k raeissi@cc iut ac irDr Morteza Shamanian Assoc Prof Advisor E mail shamanian@cc iut ac irAbstractIn this study austenitic stainless steel type 316L was welded using Gas Tungsten Arc Welding GTAW andPulsed Gas Tungsten Arc Welding PGTAW Optical observations scanning electron microscopy SEM andX Ray diffraction analysis XRD were employed to study the effect of continuous and pulse currents onmicrostructure and phase transformation in weld metal WM and heat affected zones HAZ The pulse currentresulted in finer grain and more ferrite in WM and also smaller grain growth in HAZ This can be due to thedecrease in heat input and higher cooling rate encouraged by pulse current Cyclic Potentiodynamic polarizationtests showed that the WM of sample produced by pulse current show higher corrosion and pitting resistancesthan that in sample produced by continuous current The reason is attributed to lower segregation of soluteelements such as chromium and molybdenum into the delta ferrite and also finer grain size produced in WM dueto lower heat input and higher cooling rate Both of these factors increase the stability of passive layer formed The results showed that the corrosion behavior of WM in both conditions pulse and continuous current ishigher than the base metal BM This fact is attributed to the presence of ferrite bands formed in BM due to thesegregation of alloy elements Base on the mixed potential theory the galvanic couple of HAZ WM formed insample welded by continuous current is detrimental for higher corrosion resistance due to higher grain growthand residual stress produced in HAZ The Mott schottky plots confirmed that the passive layer formed onwelded samples was an n type semiconductor The results showed that the samples showed less pittingresistance contained more oxygen vacancies in their passive film structure It is also concluded that thebreakdown of passive layer and pitting formation obey point defect model PDM Key WordsAustenitic stainless steel Gas tungsten arc welding Pulsed currents Segregation Pitting corrosion GalvanicCorrosion Mott Schottky

احمد ساعتچي، كيوان رئيسي

مرتضي شمعانيان

محمد علي گلعذار، ابراهيم حشمت دهكردي