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 the oil and gas industry, it has been established that for pipelines fabricated with carbon steels, their limitation is related to H<sub>2</sub>S and CO<sub>2</sub> environments, which is 7 ...In the oil and gas industry, it has been established that for pipelines fabricated with carbon steels, their limitation is related to H<sub>2</sub>S and CO<sub>2</sub> environments, which is 7 to 10 psia of partial pressure of <span style="white-space:normal;">CO</span><sub style="white-space:normal;">2</sub>. Therefore, in carbon steel cracking is shown, after 7 or 10 psia of partial pressure of <span style="white-space:normal;">CO</span><sub style="white-space:normal;">2</sub>. The experimental work was performed under static conditions in autoclaves within a pH of 3 to 3.8;partial pressures of 16 - 96 psi for H<sub>2</sub>S and 15 - 53 psi for <span style="white-space:normal;">CO</span><sub style="white-space:normal;">2</sub>, in the temperature range of 25<span style="white-space:nowrap;">°</span>C - 150<span style="white-space:nowrap;">°</span>C. It was observed that the average yielding stress used in Sulfide Stress Cracking (SSC) tests decreases with temperature increment. Hydrogen Induced Cracking (HIC) evaluations showed that X52 steel, under conditions, was not susceptible to HIC. Results of SSC did not show indications of cracking after exposure to sour solutions, except for the specimen exposed to high H<sub>2</sub>S and <span style="white-space:normal;">CO</span><sub style="white-space:normal;">2</sub> content (96 psi of H<sub>2</sub>S and 53 psi of <span style="white-space:normal;">CO</span><sub style="white-space:normal;">2</sub> of the partial pressure) and high temperature (150<span style="white-space:nowrap;">°</span>C). Microcracks located between the upper and lower weld beads were also observed. However, the highest average corrosion rate was 0.27 mm/year (10.6 mpy), which occurred in samples exposed to 96 psi of H<sub>2</sub>S and 53 psi of <span style="white-space:normal;">CO</span><sub style="white-space:normal;">2</sub> at 150<span style="white-space:nowrap;">°</span>C. Likewise, the highest localized corrosion (severe pitting attack) was obtained at the same environment with a corrosion rate of 4.2 mm/year (167 mpy). The oil and gas industry could use carbon steels pipelines in partial pressure higher than 10 psia.展开更多
The effect of different microstructures on the polarization resistance (Rp) and the hydrogen-induced cracking (HIC) of a micro-alloyed steel austenitized and submitted to different cooling rates was studied.Samples 19...The effect of different microstructures on the polarization resistance (Rp) and the hydrogen-induced cracking (HIC) of a micro-alloyed steel austenitized and submitted to different cooling rates was studied.Samples 19.1 x 6 x 2 mm,containing the whole thickness of the plate were extracted from a 20 mm plate and heat treated on a quenching dilatometer,were submitted to Rp and HIC corrosion tests.Both Rp and HIC tests followed as close as possible ASTM G59 and NACE standard TM0284-2003,in this case,modified only with regard to the size of the samples.Steel samples transformed from austenite by a slow cooling (cooling rate of 0.5℃.s-1) showed higher susceptibility to hydrogen-induced cracking,with large cracks in the middle of the sample propagating along segregation bands,corresponding to the centerline of the plate thickness.For cooling rates of 10℃.s-1,only small cracks were found in the matrix and micro cracks nucleated at non-metallic inclusions.For higher cooling rates (40℃.s-1) very few small cracks were detected,linked to non-metallic inclusions.This result suggests that structures formed by polygonal structures and segregation bands (were eutectoid microconstituents predominate) have higher susceptibility to HIC.Structures predominantly formed by acicular ferrite make it difficult to propagate the cracks among non-oriented and interlaced acicular ferrite crystals.Smaller segregation bands containing eutectoid products also help inhibit cracking and crack propagation;segregation bands can function as pipelines for hydrogen diffusion and offer a path of stress concentration for the propagation of cracks,frequently associated to non-metallic inclusions.Polarization resistance essays performed on the steel in theas received condition,prior to any heat treatment,showed larger differences between the regions of the plate,with a considerably lower Rp in the centerline.The austenitization heat treatments followed by cooling rates of 0.5 e 10℃.s-1 made more uniform the corrosion resistance along the thickness of the plate.The effects of heat treatments on the corrosion resistance are probably related to the microconstituent formed,allied to the chemical homogenization of the impurities concentrated on the centerline of the plate.展开更多
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 the oil and gas industry, it has been established that for pipelines fabricated with carbon steels, their limitation is related to H<sub>2</sub>S and CO<sub>2</sub> environments, which is 7 to 10 psia of partial pressure of <span style="white-space:normal;">CO</span><sub style="white-space:normal;">2</sub>. Therefore, in carbon steel cracking is shown, after 7 or 10 psia of partial pressure of <span style="white-space:normal;">CO</span><sub style="white-space:normal;">2</sub>. The experimental work was performed under static conditions in autoclaves within a pH of 3 to 3.8;partial pressures of 16 - 96 psi for H<sub>2</sub>S and 15 - 53 psi for <span style="white-space:normal;">CO</span><sub style="white-space:normal;">2</sub>, in the temperature range of 25<span style="white-space:nowrap;">°</span>C - 150<span style="white-space:nowrap;">°</span>C. It was observed that the average yielding stress used in Sulfide Stress Cracking (SSC) tests decreases with temperature increment. Hydrogen Induced Cracking (HIC) evaluations showed that X52 steel, under conditions, was not susceptible to HIC. Results of SSC did not show indications of cracking after exposure to sour solutions, except for the specimen exposed to high H<sub>2</sub>S and <span style="white-space:normal;">CO</span><sub style="white-space:normal;">2</sub> content (96 psi of H<sub>2</sub>S and 53 psi of <span style="white-space:normal;">CO</span><sub style="white-space:normal;">2</sub> of the partial pressure) and high temperature (150<span style="white-space:nowrap;">°</span>C). Microcracks located between the upper and lower weld beads were also observed. However, the highest average corrosion rate was 0.27 mm/year (10.6 mpy), which occurred in samples exposed to 96 psi of H<sub>2</sub>S and 53 psi of <span style="white-space:normal;">CO</span><sub style="white-space:normal;">2</sub> at 150<span style="white-space:nowrap;">°</span>C. Likewise, the highest localized corrosion (severe pitting attack) was obtained at the same environment with a corrosion rate of 4.2 mm/year (167 mpy). The oil and gas industry could use carbon steels pipelines in partial pressure higher than 10 psia.
文摘The effect of different microstructures on the polarization resistance (Rp) and the hydrogen-induced cracking (HIC) of a micro-alloyed steel austenitized and submitted to different cooling rates was studied.Samples 19.1 x 6 x 2 mm,containing the whole thickness of the plate were extracted from a 20 mm plate and heat treated on a quenching dilatometer,were submitted to Rp and HIC corrosion tests.Both Rp and HIC tests followed as close as possible ASTM G59 and NACE standard TM0284-2003,in this case,modified only with regard to the size of the samples.Steel samples transformed from austenite by a slow cooling (cooling rate of 0.5℃.s-1) showed higher susceptibility to hydrogen-induced cracking,with large cracks in the middle of the sample propagating along segregation bands,corresponding to the centerline of the plate thickness.For cooling rates of 10℃.s-1,only small cracks were found in the matrix and micro cracks nucleated at non-metallic inclusions.For higher cooling rates (40℃.s-1) very few small cracks were detected,linked to non-metallic inclusions.This result suggests that structures formed by polygonal structures and segregation bands (were eutectoid microconstituents predominate) have higher susceptibility to HIC.Structures predominantly formed by acicular ferrite make it difficult to propagate the cracks among non-oriented and interlaced acicular ferrite crystals.Smaller segregation bands containing eutectoid products also help inhibit cracking and crack propagation;segregation bands can function as pipelines for hydrogen diffusion and offer a path of stress concentration for the propagation of cracks,frequently associated to non-metallic inclusions.Polarization resistance essays performed on the steel in theas received condition,prior to any heat treatment,showed larger differences between the regions of the plate,with a considerably lower Rp in the centerline.The austenitization heat treatments followed by cooling rates of 0.5 e 10℃.s-1 made more uniform the corrosion resistance along the thickness of the plate.The effects of heat treatments on the corrosion resistance are probably related to the microconstituent formed,allied to the chemical homogenization of the impurities concentrated on the centerline of the plate.
