TY - CONF A1 - Madigan, Maria A1 - Mente, Tobias A1 - Böllinghaus, Thomas ED - Sommitsch, C. ED - Enzinger, N. ED - Mayr, P. T1 - Numerical Simulation of Hydrogen Assisted Stress Corrosion Cracking Originating from Pits N2 - Supermartensitic stainless steels (SMSS) are a commonly used material nowadays for building offshore structures, i.e. pipelines in the oil and gas industry. The harsh and corrosive environments in oil and gas applications require the correct combination of alloys to attain the desired properties of steel, including high strength and good corrosion properties, even in severe sour service conditions. Welding is the most commonly used method in joining offshore components, depending on requirements requiring strength or fitting. It has been shown that the heat affected zone (HAZ) is more susceptible to certain types of corrosion, including pitting corrosion, especially during severe sour service where a high pH and lower H2S values in the flow medium can lead to pitting corrosion in the HAZ of welded structures. Subsequent hydrogen uptake in the pits can cause cracks to initiate and propagate, leading to rupture of pipelines or catastrophic failures of structures, even at low mechanical loads. Offshore standards allow a certain amount of corrosion, including pitting, to be present before action is required, however the extent of pitting corrosion is not identified by performing visual inspection alone as the subsurface pit diameter may be vastly greater than the pit diameter at the surface. The critical conditions which lead to crack initiation and propagation from a pit with hydrogen uptake are currently not known. Therefore, pitting corrosion and subsequent crack initiation are a danger to the safety of structures. The interest in this phenomenon has resulted in many experimental studies and numerical simulations. Several numerical models of pitting corrosion and hydrogen uptake resulting in crack initiation are already in existence, but these two phenomena are regularly modelled individually. Thus, a model enabling simulation of both phenomena simultaneously would be of great benefit. Hence, the goal of this study is to develop a model enabling simulation of pit growth and crack initiation, considering hydrogen uptake in the pit from a corrosive environment. As a first step, this paper presents an investigation into various parameters, which influence crack initiation at pits. These crack critical parameters include: pit geometry, pit location, mechanical load and hydrogen transport into the microstructure. The results will help to identify critical conditions for crack initiation starting at the pit and developing measures to avoid hydrogen assisted cracking (HAC). T2 - 12th International Seminar Numerical Analysis of Weldability CY - Graz, Austria DA - 23.09.2018 KW - Hydrogen Assisted Cracking (HAC) KW - Pitting KW - Supermartensitic Stainless Steel (SMSS) KW - Numerical Simulation PY - 2019 SN - 978-3-85125-615-4 SN - 978-3-85125-616-1 SN - 2410-0544 VL - 12 SP - 443 EP - 464 PB - Verlag der Technischen Universität Graz CY - Graz (Österreich) AN - OPUS4-48721 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Madigan, Maria A1 - Mente, Tobias A1 - Böllinghaus, Thomas T1 - Numerical simulation of hydrogen assisted stress corrosion cracking originating from pits N2 - Supermartensitic stainless steels (SMSS) are a commonly used material nowadays for building offshore structures, i.e. pipelines in the oil and gas industry. The harsh and corrosive environments in oil and gas applications require the correct combination of alloys to attain the desired properties of steel, including high strength and good corrosion properties, even in severe sour service conditions. Welding is the most commonly used method in joining offshore components, depending on requirements requiring strength or fitting. It has been shown that the heat affected zone (HAZ) is more susceptible to certain types of corrosion, including pitting corrosion, especially during severe sour service where a high pH and lower H2S values in the flow medium can lead to pitting corrosion in the HAZ of welded structures. Subsequent hydrogen uptake in the pits can cause cracks to initiate and propagate, leading to rupture of pipelines or catastrophic failures of structures, even at low mechanical loads. Offshore standards allow a certain amount of corrosion, including pitting, to be present before action is required, however the extent of pitting corrosion is not identified by performing visual inspection alone as the subsurface pit diameter may be vastly greater than the pit diameter at the surface. The critical conditions which lead to crack initiation and propagation from a pit with hydrogen uptake are currently not known. Therefore, pitting corrosion and subsequent crack initiation are a danger to the safety of structures. The interest in this phenomenon has resulted in many experimental studies and numerical simulations. Several numerical models of pitting corrosion and hydrogen uptake resulting in crack initiation are already in existence, but these two phenomena are regularly modelled individually. Thus, a model enabling simulation of both phenomena simultaneously would be of great benefit. Hence, the goal of this study is to develop a model enabling simulation of pit growth and crack initiation, considering hydrogen uptake in the pit from a corrosive environment. As a first step, this paper presents an investigation into various parameters, which influence crack initiation at pits. These crack critical parameters include: pit geometry, pit location, mechanical load and hydrogen transport into the microstructure. The results will help to identify critical conditions for crack initiation starting at the pit and developing measures to avoid hydrogen assisted cracking (HAC). T2 - 12th International Seminar “Numerical Analysis of Weldability” CY - Seggau, Austria DA - 23.09.2018 KW - Hydrogen Assisted Cracking (HAC) KW - Pitting KW - Supermartensitic Stainless Steel (SMSS) KW - Numerical Simulation PY - 2018 AN - OPUS4-46651 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -