Hydrogen production 2 hydrogen diffusion 3 hydrogen trapping in defaults 4 increasing of pressure 5 cracking hydrogen induced cracking hic 10. Recent experience has demonstrated the risk of sscc and hic, sometimes known as hydrogen embrittlement he, of low strength steels subject to high residual stress derived from fabrication techniques. Hydrogen induced stress cracking hisc resistance and. The authors conducted extensive analyses to explore the effects of metallurgical factors on the resistance of line pipe steels to hydrogen induced cracking hic and sulfide stress cracking ssc. Steels with different microstructures were produced by a thermomechanically controlled process tmcp from two different heats, which had different levels of nonmetallic inclusions. It is made up of a series of hic hydrogen induced cracking cracks that are stacked perpendicularly in the direction of through wall cracks and driven by high residual or applied stresses. The ssc of medium strength steels has been a continuing source of trouble in the oil fields, and from these troubles has evolved in international standards 6. Hic may occasionally be delayed beyond the normal timescale of a few hours to a day, to allow for the diffusive migration of hydrogen into and, if not trapped, out of the steel. Processes or conditions involving wet hydrogen sulfide, i. Stress oriented hydrogen induced cracking sohic stress orientated hydrogen induced cracking occurs in the area of grain enlargement in weld heat affected zones. The hydrogen atom is the smallest of all atoms and hydrogen attack is similarly insidious and hidden from simple inspection techniques. Environmental cracking can occur with a wide variety of metals and alloys and includes all of the types of corrosion failures listed below.
Environmental cracking is a general term that includes. Sour service is a environment containing water and h2s hydrogen sulfide with pressure of 50ppm if the presence of hydrogen sulfide i. Production of hic resistant steels total materia article. This can occur during elevatedtemperature thermal treatments and in service during electroplating, contact with maintenance chemicals, wet h 2 s, corrosion reactions, cathodic protection, and operating in highpressure hydrogen containing environments. Also high strength structural steels which are welded are exposed to a certain hydrogen pickup which means a risk at fracture and blistering due to hic. Another variant of hydrogenrelated corrosive damage sulphide stress corrosion cracking affects high strength steels, in which hydrogen migrates to a crack formed on the steels surface. It can occur at relatively low temperatures, largely as a result of atomic hydrogen from wet h2s corrosion reactions which enter the steel and collect at inclusions or. Our hic quality plate is ordered to meet more stringent requirements when hydrogen induced cracking tests per the latest nace tm0284 are needed or sulfide stress corrosion cracking tests in accordance with the latest nace standards tm0177 are required. At the same time the h2s also reacts with the iron of the steel wall.
Hfi were selected for hydrogen induced cracking hic tests. Hydrogeninduced cracking hic has been studied phenomenologically. It involves atomic hydrogen, which is the smallest atom, that diffuses into a metallic structure. It is characterized by the brittle fracture of a normally ductile alloy under sustained load in the presence of hydrogen. The effect of microstructure on hic is discussed for steels having two different levels of nonmetallic inclusions. Liquid metal cracking lmc, usually a physicochemical process. Sour cracking hic, sulfide stress corrosion cracking sscc environmentally assisted cracking can also occur internally in pipelines. Stressoriented, hydrogeninduced cracking sohic is a specialized type of hic that has in some cases resulted in throughwall cracks in carbon steel pressure vessels manufacturers offer steels made with very low sulfur contents and calcium treated for inclusion shape control to resist hic. Sulfide stress cracking ssc vs hydrogen induced cracking. The pressure of the hydrogen gas causes localized internal cracks, known as hydrogen induced cracks. Preventing hydrogen induced cracking welding answers. Hydrogen combines with carbon within the alloy and forms methane.
Stress orientated hydrogen induced cracking sohic is a manifestation of sulfide stress cracking ssc in cmn steels by a mechanism involving the linking of planar cracks normal to the primary propagation direction of the crack. Hydrogen induced cracking hic is a form of wet h2s hydrogen sulfide cracking caused by the blistering of a metal due to a high concentration of hydrogen. Stress corrosion cracking of gas pipelines 3 minute 2014 thesis finalist. Following aqueous corrosion reactions in the presence of h2s on the pipe internal surface, atomic hydrogen is produced and absorbed in the pipe steel.
Hydrogeninduced cracking an overview sciencedirect topics. The formation of subsurface planar cavities, called hydrogen blisters, in a metal resulting from excessive internal hydrogen pressure. Hydrogen induced cracking hic damage is a degradation mechanism active in the oil and gas industry. Investigation of stressoriented hydrogeninduced cracking sohic. Effect of residual stresses on the hic resistance of erw pipes for. In general, the susceptibility to hic is affected by th e tensil strength, diffusible hydrogen content, microstructure and residual stress in the weld metal, and for more accurate evaluation, those factors should be investigated at the crack initia tion site of the weld metal. Simply put, hydrogen induced cracking damage increases as the level of hydrogen sulphide increases. Hydrogeninduced cracking hic refers to the internal cracks brought about by material trapped in budding hydrogen atoms. Hydrogen induced cracking steel features, applications. Mechanism of cracking in the presence of h2s, the process of cracking hic can be divided in to 5 stages 1 corrosion. While these metals may normally be ductile in nature, the presence of hydrogen in a corroded environment can cause it to crack. Hydrogen induced cracking hic from advanced ndt solutions. Hydrogeninduced cracking susceptibility in highstrength. Axial crack inspection pipeline integrity management.
In the first case hic, it is generally recognized that the resistance of steels depends mainly on their microstructural features nonmetallic. Corrosionpedia what is hydrogeninduced cracking hic. Hydrogen induced cracking hic and stressoriented hydrogen. Hic is prevalent in wet h 2 s environments, which is often known as sour service and such cracking over a prolonged period of time without inspection, will reach a critical point and the steel component i. Stress oriented hydrogen induced cracking sohic is similar to hic but. Naceastm g193 1 includes the following description of hydrogen blistering. The first type is commonly referred to as hydrogen induced cracking hic and can occur where little or no applied or residual tensile stress exists. It is a form of hydrogen related cracking and can have two distinct morphologies. This type of cracking tends to appear on the surface as small blisters connected by cracks and it can occur when atomic hydrogen enters into the steel. The methane molecules create a pressure which leads to embrittlement and even cracking.
The blistering damage tends to form parallel to the surface and to the direction of hoop stress. Susceptibility to sohic for linepipepressure vessel steels twi. O ur last post factors influencing hydrogen induced cracking went over the factors that contribute to hydrogeninduced cracking. Hydrogeninduced craking hic, also referred to as hydrogen stress cracking or static fatigue, is a typical form of hydrogen embrittlement. Hydrogen induced cracks either follow a linear or stepwise path within the material, hence the term stepwise cracking. Hydrogen induced cracking hic and sulphide stress cracking ssc represent two kinds of a specific hydrogen provoked damage that are frequently met in the petroleum and refinery industry. Hydrogen induced cracking hic and stressoriented hydrogen induced. Sohic is a type of cracking that can easily lead to failure and needs to be mitigated. Stressoriented hydrogeninduced cracking an overview. It involves the ingress of hydrogen into a component, an event that can seriously reduce the ductility and loadbearing capacity, cause cracking and catastrophic brittle failures at stresses below the yield stress of susceptible materials. Hic is susceptible to be presented in the sour gas system because of the. Susceptibility to sohic for linepipepressure vessel. Stress oriented hydrogen induced cracking sohic behavior of heat affected zone haz of l360mcs steel in wet h2s environment was studied by separating crack, sem and eds. Particular attention was given to largescale behavior vs behavior for smallscale laboratory test specimens under an applied tensile stress.
Hydrogen induced cracking of low strength steels in. If you recall, we mentioned you need all three factors to be present in order to have hic. Largescale wet hydrogen sulfide cracking performance. As we know that both form of cracking are due to the absorption of atomic hydrogen that is produced by. More often, fracture occurs at sustained loads below the yield strength of the material. Our engineers and technicians utilize their academic training, field experience, and advanced analysis tools to identify and help control modes of corrosion and environmental degradation of materials that can lead to component or systemwide failures with our corrosion engineering services. Effect of microstructure on hydrogeninduced cracking of. This paper presents the actual performance of such techniques, for onstream inspection of pressure vessels in wet h 2 s service suffering from hydrogen induced cracking hic or stress oriented hydrogen induced crack sohic. Atomic hydrogen diffuses into the pipe wall and recombining of hydrogen atoms into hydrogen molecules takes place at inclusions or laminations causing blistering. This is a type of deterioration which can be linked to corrosion and corrosioncontrol processes. Ultrasonic detection of hydrogen induced cracking hic in. The resulting highpressure within these blisters promotes crack growth. Adsorbed hydrogen species recombine to form hydrogen molecules, creating pressure from within the metal. St specializes in corrosion tests as per nace and astm.
It is made up of a series of hic hydrogen induced cracking cracks that are stacked perpendicularly in the direction of through wall cracks and driven by high. Stressoriented, hydrogeninduced cracking sohic is a specialized type of hic that has in some cases resulted in throughwall cracks in carbon steel pressure. Sulfide stress cracking ssc vs hydrogen induced cracking hlc posted in refining, hydrocarbons, oil, and gas. Ultrasonic detection of hydrogen induced cracking hic. Hic is caused by hydrogen resulting from suitable chemical components in the pipeline medium e. Hydrogen induced cracking hic is a common form of wet h2s cracking caused by the blistering of a metal due to a high concentration of hydrogen. Stressoriented hydrogeninduced cracking of l360qs steel. This form of cracking is often seen in the low hardness heat affected zone haz region of welds. Hydrogen induced cracking hydrogen induced cracking hic can occur in metal equipment due to high concentrations of hydrogen. Corrosion engineering stress engineering services, inc. Hydrogen stress cracking occurs when hydrogen penetrates highstrength or hardened metal in a state of tensile stress. This pressure can increase to levels where the metal has reduced ductility, toughness, and tensile strength, up to the point where it cracks open hydrogeninduced cracking, or hic. However, under certain stress and material conditions, the cracks can be arranged in a ladderlike array known as stress orientated hydrogen induced cracking sohic. We will now go over how to prevent hic from happening.
Sohlc appears to be related to segregation of microalloying elements in the banded steel microstructure. The most common conditions for these are sour environments. Hydrogeninduced cracking results from atomic hydrogen being absorbed by solid metals. Corrosion loops were established for the sour environment and revealed that hic is one of the potential damage mechanisms that could affect the sour gas system.
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