The hydrogen-induced cracking （HIC） behavior of X80 pipeline steel was studied by means of electrochemical charging, hydrogen permeation tests, tension test, and scanning electron microscopy （SEM）. The experimenta...The hydrogen-induced cracking （HIC） behavior of X80 pipeline steel was studied by means of electrochemical charging, hydrogen permeation tests, tension test, and scanning electron microscopy （SEM）. The experimental results indicate that the increase of charging time and charging current density or the decrease of the solution pH value leads to an increase of the hydrogen content in X80 steel, which plays a key role in the initiation and propagation of HIC. It is found that the majority of macro-inclusions within the as-used X80 steel do not constitute a direct threat to HIC except aluminum oxides, which directly or indirectly lead to HIC. The hydrogen trap density at room temperature is estimated to be pretty high, and this is an essential reason why the steel is sensitive to HIC. After hydrogen charging, the elongation loss rate and area reduction of X80 steel decline obviously, taking a noticeable sign of hydrogen-induced plasticity damages. It is demonstrated that the losses of these plastic parameters have a linear relation to the fracture size due to hydrogen.展开更多
Hydrogen-induced cracking (HIC) of Fe3Al alloy was studied by in situ transmission electron microscope (TEM). Electron transparent specimens were mounted onto a constant displacement device. Stress was applied to the ...Hydrogen-induced cracking (HIC) of Fe3Al alloy was studied by in situ transmission electron microscope (TEM). Electron transparent specimens were mounted onto a constant displacement device. Stress was applied to the specimen by using a bolt through the device. The results showed that hydrogen enhanced the dislocation emission and motion in Fe3Al alloy. A dislocation free zone (DFZ) was formed following the dislocation emission. Microcrack initiated in the DFZ or at the main crack tip when the emission reached a critical extension. Hydrogen played an important role in the process of brittle fracture of Fe3Al alloy.展开更多
In the present work, the effects of chemical compositions on the hydrogen blistering and hydrogen induced cracking of A350LF2 steel with different S contents were studied. Four types of A350LF2 steels were evaluated b...In the present work, the effects of chemical compositions on the hydrogen blistering and hydrogen induced cracking of A350LF2 steel with different S contents were studied. Four types of A350LF2 steels were evaluated by immersing samples in H2S-saturated NACE solution. The hydrogen blistering, crack length rate(CLR), crack thickness rate(CTR) and crack sensitivity rate(CSR) were evaluated. The results show that there are many hydrogen blisters on the sample surface with S content of 0.021%, a few on the sample surface with S content of 0.019% and 0.012% and no one on the surface with S content of 0.002%. There were 12, 2 and 1 strips of cracks of longer than 0.3 mm on the evaluated cross sections with S content of 0.021%, 0.019% and 0.012%, respectively. There was no any crack in the sample with 0.002% S. The corrosion rate was also evaluated. The S content has no obvious influence on the corrosion rate.展开更多
The effect of hydrogen on the fractttre behaviors of Incoloy alloy 825 was investigated by means of slow strain rate testing （SSRT） Hydrogen was introduced into the sample by electrochemical charging. The results sh...The effect of hydrogen on the fractttre behaviors of Incoloy alloy 825 was investigated by means of slow strain rate testing （SSRT） Hydrogen was introduced into the sample by electrochemical charging. The results show that surface microcracks form gradually during ag- ing at room temperature when desorption of hydrogen takes place after hydrogen charging at a current density of 5 mA/cm^2 for 24 h. SSRT shows that the increase of ductility loss is significantly obvious as the hydrogen charging current density increases. Scanning electron microscopy （SEM） images reveal ductile fracture in the pre-charged sample with low current densities, while the fracture includes small quasi-cleavage regions and tends to be brittle fracture as the hydrogen charging current density increases to 5 mA/cm^2.展开更多
In this paper, the microstructure and hardness of HG980D heat-affected zone （HAZ） at different cooling rate t8/3 were studied, the implant critical fracture stress under three diffusible hydrogen conditions were mea...In this paper, the microstructure and hardness of HG980D heat-affected zone （HAZ） at different cooling rate t8/3 were studied, the implant critical fracture stress under three diffusible hydrogen conditions were measured, and the hydrogeninduced cracking （H1C） fructograph of steel HG980D were analyzed, The experimental results show that martensite exists in HAZ of HG980D till ts/3 ≥ 150 s, the harden quenching tendency of HG980D is greater; The implant critical fracture stress is related to difJhsible hydrogen content significantly, at low hydrogen level, high restraint stress is needed to nucleate HIC, the fraetograph is mainly mierovoid coalescence, bat at high hydrogen level, only small restraint stress can cause H1C occurrence, the fractograph is mainly quasicleavage. It is very important to choose ultra-low hydrogen welding consumable to weld steel HG980D to prevent hydrogen-induced cracking.展开更多
Dezincification layer formed during corrosion or stress corrosion cracking (SCC) of brass in an ammonia solution could induce an additive stress. The effect of hydrogen on the dezincification layer induced stress and ...Dezincification layer formed during corrosion or stress corrosion cracking (SCC) of brass in an ammonia solution could induce an additive stress. The effect of hydrogen on the dezincification layer induced stress and the susceptibility to SCC were studied. The dezincification layer induced stress was measured using the deflection method and the flowing stress differential method, respectively. The latter measures the difference between the flowing stress of a specimen before unloading and the yield stress of the same specimen after unloading and forming a dezincification layer. The susceptibility to SCC was measured using slow strain rate test. Results show that both the dezincification layer induced stress and the susceptibility to SCC increase with increasing hydrogen concentration in a specimen. This implies that hydrogen enhanced dezincification layer induced stress is consistence with the hydrogen increased susceptibility to SCC of brass in the ammonia solution.展开更多
1.IntroductionSo far there are few people who studythe relationship between the criticalhydrogen concentration and the stress forhvdrogen induced cracking (CCHIC)quantitatively.Several researchers have cal-culated the...1.IntroductionSo far there are few people who studythe relationship between the criticalhydrogen concentration and the stress forhvdrogen induced cracking (CCHIC)quantitatively.Several researchers have cal-culated the CCHIC of steels under no stressby means of H permeation method,but no展开更多
For 308L and 347L weld metals of austenitc stainless steels (ASS), hydrogen induced cracking (HIC) occurred during dynamically charging under constant load. The threshold stress intensity for HIC, Km, decreased linear...For 308L and 347L weld metals of austenitc stainless steels (ASS), hydrogen induced cracking (HIC) occurred during dynamically charging under constant load. The threshold stress intensity for HIC, Km, decreased linearly with the logarithm of the concentration of diffusible hydrogen C0 in the weld metals and the rolled plate of type 304L ASS, i.e., KIH=85.2-10.71nC0 (308L), KIH=76.1-9.31n C0(347L), and KIH=91.7-10.11nC0(304L). The fracture mode for HIC in the three type of ASS changed from ductile to brittle with the decrease in the applied stress intensity KI or/and the increase in C0. The boundary line between ductile and brittle fracture surfaces was KI-54+25exp(-C0/153)=0.展开更多
The relation between grain size and strength of the duplex stainless steels and influence of grain size on properties of hydrogen induced cracking in these steels have been investigated. The Hall-Petch relation betwee...The relation between grain size and strength of the duplex stainless steels and influence of grain size on properties of hydrogen induced cracking in these steels have been investigated. The Hall-Petch relation between grain size and strength of the steels is also followed.The susceptibility to hydrogen induced cracking of the steels increases with increasing grain size.展开更多
Hydrogen induced cracking(HIC)of 0.3% C,1% Cr,1% Mn,1% Si high strength steel has been studied under simple mode Ⅰ,mode Ⅱ and(Ⅰ+Ⅱ)mixed mode loading conditions.Af- ter being hydrogen-charged in IN H_2SO_4 solution...Hydrogen induced cracking(HIC)of 0.3% C,1% Cr,1% Mn,1% Si high strength steel has been studied under simple mode Ⅰ,mode Ⅱ and(Ⅰ+Ⅱ)mixed mode loading conditions.Af- ter being hydrogen-charged in IN H_2SO_4 solution,the material behaved hydrogen embrittlement in all the cases studied.The threshold K_(ⅡH)/K_(ⅡX) of HIC under mode Ⅱ load- ing was 0.27,which was nearly the same as that K(ⅠH)/K_(ⅠX)=0.29 under mode Ⅰ loading. While the thresholds of-HIC under(Ⅰ+Ⅱ)mixed mode loading were 0.36,0.41 and 0.37 cor- responding to the K_Ⅱ/K_Ⅰ ratio of 0.27,0.4 and O.81.The results show that simple mode Ⅰ or mode Ⅱ loading is more susceptible to hydrogen embrittlement than(Ⅰ+Ⅱ)mixed mode. For explaining the experimental results,the effects of triaxial stress as well as plastic deformation ahead of crack tip has been discussed.展开更多
The threshold stress intensity of stress corrosion cracking(SCC) for 40 CrMo steel in 3.5%NaCl solution decreased exponentially with the increase of yield strength.The threshold stress intensity of hydrogen-induced cr...The threshold stress intensity of stress corrosion cracking(SCC) for 40 CrMo steel in 3.5%NaCl solution decreased exponentially with the increase of yield strength.The threshold stress intensity of hydrogen-induced cracking during dynamical charging for 40 CrMo steel decreased linearly with the logarithm of the concentration of diffusible hydrogen.This equation was also applicable to SCC of high strength steel in aqueous solution.The critical hydrogen enrichment concentration necessary for SCC of high strength steel in water decreased exponentially with the increase of yield strength.Based on the results,the relationship between K_(ISCC) and σ_(ys) could be deduced.展开更多
The relationship between the stress intensity factor K_1~* required for brittle crack initiation and propa- gation and the fractal dimension D_F of the fracture surface was derived,i.e, InK_1~*=(1/2)In2γE'+(1/2)I...The relationship between the stress intensity factor K_1~* required for brittle crack initiation and propa- gation and the fractal dimension D_F of the fracture surface was derived,i.e, InK_1~*=(1/2)In2γE'+(1/2)In(d_f/L_0)(1-D_F) The real surface energy can be calculated based on the measured linear relation of the InK_1~* vs D_F, The equation is not only suitable for the overload fracture but also for the delayed fracture,e.g. hydrogen induced cracking (HIC) and stress corrosion cracking (SCC).The experiment results showed that the hydrogen induced delayed cracking occurred in the Ti-24AI-11 Nb alloy during dy- namic charging,and the threshold stress intensity factor was very low,i.e..K_(IH)/K_(IC)= 0.43.The ex- perimental relationship between the stress intensity factor K_1~* and D_F was consistent with the theo- retical equation.展开更多
基金supported by the National Natural Science Foundation of China (No.50401016)
文摘The hydrogen-induced cracking （HIC） behavior of X80 pipeline steel was studied by means of electrochemical charging, hydrogen permeation tests, tension test, and scanning electron microscopy （SEM）. The experimental results indicate that the increase of charging time and charging current density or the decrease of the solution pH value leads to an increase of the hydrogen content in X80 steel, which plays a key role in the initiation and propagation of HIC. It is found that the majority of macro-inclusions within the as-used X80 steel do not constitute a direct threat to HIC except aluminum oxides, which directly or indirectly lead to HIC. The hydrogen trap density at room temperature is estimated to be pretty high, and this is an essential reason why the steel is sensitive to HIC. After hydrogen charging, the elongation loss rate and area reduction of X80 steel decline obviously, taking a noticeable sign of hydrogen-induced plasticity damages. It is demonstrated that the losses of these plastic parameters have a linear relation to the fracture size due to hydrogen.
文摘Hydrogen-induced cracking (HIC) of Fe3Al alloy was studied by in situ transmission electron microscope (TEM). Electron transparent specimens were mounted onto a constant displacement device. Stress was applied to the specimen by using a bolt through the device. The results showed that hydrogen enhanced the dislocation emission and motion in Fe3Al alloy. A dislocation free zone (DFZ) was formed following the dislocation emission. Microcrack initiated in the DFZ or at the main crack tip when the emission reached a critical extension. Hydrogen played an important role in the process of brittle fracture of Fe3Al alloy.
文摘In the present work, the effects of chemical compositions on the hydrogen blistering and hydrogen induced cracking of A350LF2 steel with different S contents were studied. Four types of A350LF2 steels were evaluated by immersing samples in H2S-saturated NACE solution. The hydrogen blistering, crack length rate(CLR), crack thickness rate(CTR) and crack sensitivity rate(CSR) were evaluated. The results show that there are many hydrogen blisters on the sample surface with S content of 0.021%, a few on the sample surface with S content of 0.019% and 0.012% and no one on the surface with S content of 0.002%. There were 12, 2 and 1 strips of cracks of longer than 0.3 mm on the evaluated cross sections with S content of 0.021%, 0.019% and 0.012%, respectively. There was no any crack in the sample with 0.002% S. The corrosion rate was also evaluated. The S content has no obvious influence on the corrosion rate.
文摘The effect of hydrogen on the fractttre behaviors of Incoloy alloy 825 was investigated by means of slow strain rate testing （SSRT） Hydrogen was introduced into the sample by electrochemical charging. The results show that surface microcracks form gradually during ag- ing at room temperature when desorption of hydrogen takes place after hydrogen charging at a current density of 5 mA/cm^2 for 24 h. SSRT shows that the increase of ductility loss is significantly obvious as the hydrogen charging current density increases. Scanning electron microscopy （SEM） images reveal ductile fracture in the pre-charged sample with low current densities, while the fracture includes small quasi-cleavage regions and tends to be brittle fracture as the hydrogen charging current density increases to 5 mA/cm^2.
文摘In this paper, the microstructure and hardness of HG980D heat-affected zone （HAZ） at different cooling rate t8/3 were studied, the implant critical fracture stress under three diffusible hydrogen conditions were measured, and the hydrogeninduced cracking （H1C） fructograph of steel HG980D were analyzed, The experimental results show that martensite exists in HAZ of HG980D till ts/3 ≥ 150 s, the harden quenching tendency of HG980D is greater; The implant critical fracture stress is related to difJhsible hydrogen content significantly, at low hydrogen level, high restraint stress is needed to nucleate HIC, the fraetograph is mainly mierovoid coalescence, bat at high hydrogen level, only small restraint stress can cause H1C occurrence, the fractograph is mainly quasicleavage. It is very important to choose ultra-low hydrogen welding consumable to weld steel HG980D to prevent hydrogen-induced cracking.
文摘Dezincification layer formed during corrosion or stress corrosion cracking (SCC) of brass in an ammonia solution could induce an additive stress. The effect of hydrogen on the dezincification layer induced stress and the susceptibility to SCC were studied. The dezincification layer induced stress was measured using the deflection method and the flowing stress differential method, respectively. The latter measures the difference between the flowing stress of a specimen before unloading and the yield stress of the same specimen after unloading and forming a dezincification layer. The susceptibility to SCC was measured using slow strain rate test. Results show that both the dezincification layer induced stress and the susceptibility to SCC increase with increasing hydrogen concentration in a specimen. This implies that hydrogen enhanced dezincification layer induced stress is consistence with the hydrogen increased susceptibility to SCC of brass in the ammonia solution.
文摘1.IntroductionSo far there are few people who studythe relationship between the criticalhydrogen concentration and the stress forhvdrogen induced cracking (CCHIC)quantitatively.Several researchers have cal-culated the CCHIC of steels under no stressby means of H permeation method,but no
基金This project was supported by the Special Fund for the MajorState Basic Research projects(No. G19990650).
文摘For 308L and 347L weld metals of austenitc stainless steels (ASS), hydrogen induced cracking (HIC) occurred during dynamically charging under constant load. The threshold stress intensity for HIC, Km, decreased linearly with the logarithm of the concentration of diffusible hydrogen C0 in the weld metals and the rolled plate of type 304L ASS, i.e., KIH=85.2-10.71nC0 (308L), KIH=76.1-9.31n C0(347L), and KIH=91.7-10.11nC0(304L). The fracture mode for HIC in the three type of ASS changed from ductile to brittle with the decrease in the applied stress intensity KI or/and the increase in C0. The boundary line between ductile and brittle fracture surfaces was KI-54+25exp(-C0/153)=0.
文摘The relation between grain size and strength of the duplex stainless steels and influence of grain size on properties of hydrogen induced cracking in these steels have been investigated. The Hall-Petch relation between grain size and strength of the steels is also followed.The susceptibility to hydrogen induced cracking of the steels increases with increasing grain size.
文摘Hydrogen induced cracking(HIC)of 0.3% C,1% Cr,1% Mn,1% Si high strength steel has been studied under simple mode Ⅰ,mode Ⅱ and(Ⅰ+Ⅱ)mixed mode loading conditions.Af- ter being hydrogen-charged in IN H_2SO_4 solution,the material behaved hydrogen embrittlement in all the cases studied.The threshold K_(ⅡH)/K_(ⅡX) of HIC under mode Ⅱ load- ing was 0.27,which was nearly the same as that K(ⅠH)/K_(ⅠX)=0.29 under mode Ⅰ loading. While the thresholds of-HIC under(Ⅰ+Ⅱ)mixed mode loading were 0.36,0.41 and 0.37 cor- responding to the K_Ⅱ/K_Ⅰ ratio of 0.27,0.4 and O.81.The results show that simple mode Ⅰ or mode Ⅱ loading is more susceptible to hydrogen embrittlement than(Ⅰ+Ⅱ)mixed mode. For explaining the experimental results,the effects of triaxial stress as well as plastic deformation ahead of crack tip has been discussed.
基金Item Sponsored by Special Funds for State Major Basis Research(G19990650)
文摘The threshold stress intensity of stress corrosion cracking(SCC) for 40 CrMo steel in 3.5%NaCl solution decreased exponentially with the increase of yield strength.The threshold stress intensity of hydrogen-induced cracking during dynamical charging for 40 CrMo steel decreased linearly with the logarithm of the concentration of diffusible hydrogen.This equation was also applicable to SCC of high strength steel in aqueous solution.The critical hydrogen enrichment concentration necessary for SCC of high strength steel in water decreased exponentially with the increase of yield strength.Based on the results,the relationship between K_(ISCC) and σ_(ys) could be deduced.
文摘The relationship between the stress intensity factor K_1~* required for brittle crack initiation and propa- gation and the fractal dimension D_F of the fracture surface was derived,i.e, InK_1~*=(1/2)In2γE'+(1/2)In(d_f/L_0)(1-D_F) The real surface energy can be calculated based on the measured linear relation of the InK_1~* vs D_F, The equation is not only suitable for the overload fracture but also for the delayed fracture,e.g. hydrogen induced cracking (HIC) and stress corrosion cracking (SCC).The experiment results showed that the hydrogen induced delayed cracking occurred in the Ti-24AI-11 Nb alloy during dy- namic charging,and the threshold stress intensity factor was very low,i.e..K_(IH)/K_(IC)= 0.43.The ex- perimental relationship between the stress intensity factor K_1~* and D_F was consistent with the theo- retical equation.
