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Hydrogen-assisted stress corrosion cracking of high strength steel
KTH, School of Chemical Science and Engineering (CHE).
2011 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Väte-inducerad spänningskorrosion på höghållfasta stål (Swedish)
Abstract [en]

In this work, Slow Strain Rate Test (SSRT) testing, Light Optical Microscopy (LOM) and Scanning Electron Microscopy (SEM) were used to study the effect of micro-structure, corrosive environments and cathodic polarisation on stress corrosion cracking (SCC) of two grades of high strength steels, Type A and Type B. Type A is manufactured by quench and tempered (Q&T) method. Type B, a normalize steel was used as reference. This study also supports electrochemical polarisation resistance method as an effective testing technique for measuring the uniform corrosion rate. SSRT samples were chosen from base metal, weld metal and Heat Affected Zone (HAZ). SSRT tests were performed at room temperature under free corrosion potential and cathodic polarisation using 4 mA/cm2 in 1 wt% and 3.5 wt% NaCl solutions. From the obtained corrosion rate measurements performed in 1 wt% and 3.5 wt% NaCl solutions it was observed that increased chloride concentration and dissolved oxygen content enhanced the uniform corrosion for all tested materials. Moreover, the obtained results from SSRT tests demonstrate that both Q&T and normalized steels were not susceptible to SCC in certain strain rate(1×10-6s-1) in 1 wt% and 3.5 wt% NaCl solutions under free corrosion potential. It was con-firmed by a ductile fracture mode and high reduction in area. The weld metal of Type A with acicular ferrite (AF), pro-eutectoid (PF) and bainite microstructure showed higher susceptibility to hydrogen assisted stress corrosion cracking compared to base metal and HAZ. In addition, typical brittle intergranular cracking with small reduction in area was observed on the fracture surface of the Type A due to hydrogen charging.

Place, publisher, year, edition, pages
Keyword [en]
Hydrogen embrittlement, hydrogen induced cracking, stress corrosion cracking, high strength steel, uniform corrosion, SSRT, hydrogen charging, fractography, hydrogen degradation
National Category
Corrosion Engineering
URN: urn:nbn:se:kth:diva-50416OAI: diva2:461870
Subject / course
Corrosion Science
Educational program
Master of Science - Materials Science and Engineering
Physics, Chemistry, Mathematics
Available from: 2011-12-05 Created: 2011-12-05 Last updated: 2011-12-06Bibliographically approved

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