4223

3994

كارشناسي ارشد

خوردگي و حفاظت مواد

اصفهان : دانشگاه صنعتي اصفهان، دانشكده مواد

1387

هشت، 94، [II] ص. : مصور، جدول، نمودار

ص. ع. به : فارسي و انگليسي

محمد علي گلعذار، احمد ساعتچي

22/7/1387

ابراهيم حشمت دهكردي، كيوان رئيسي

مهندسي مواد

ID3994

به فارسي و انگليسي : قابل رويت در نسخه ديجيتال

Abstract The effect of hydrogen on the stress corrosion cracking SCC of API X 65 pipelinesteel in near neutral pH environments was studied using cyclic voltammetry hydrogen electrochemical oxidation current measurements and slow strain rate tests SSRT All the tests were performed in solution consisted of 0 1 0 01 and 0 005 Msodium bicarbonate NaHCO3 at both room temperature and 60 C The oxidationcurrents were obtained for the hydrogen pre charged specimens maintained at acertain positive potential in dilute NaOH electrolyte Hydrogen concentrations incathodically pre charged specimens were estimated by calculating the area under thecurrent curve The results showed that hydrogen oxidation current increased withdecreasing solution concentration and was maximum for 0 005 M NaHCO3 at 60 C Combined with SSRT results it is found that the high susceptibility to SCC is alwaysconnected to a high hydrogen concentration in steel In addition the fracture surfacesof specimens were observed in a scanning electron microscope SEM Specimentested in air exhibited a ductile type of failure conversely those tested in corrosivesolution showed brittle fracture composed of microcracks just near the surface Thesemicrocracks were found more frequently in the specimen tested in 0 005 M NaHCO3 so it might be due to the effect of high hydrogen concentration in steel

محمد علي گلعذار، احمد ساعتچي

ابراهيم حشمت دهكردي، كيوان رئيسي