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tempered (QT). Following the promise of these preliminary tests a schedule of low loop tests, more representative of oil-ield conditions, was conducted on the steels showing most potential, and the results are given in Figure 5. Again the alloyed steels exhibited more resist- ance to corrosion than X70 steel, and moreover, the best steels had a corrosion rate 5 times better than that of X70, meeting the initial target set. The tests also showed the initial corrosion rate of the experimental steels decreasing with time, whereas that of the X70 steel increased with time (Figure 6). This suggests the development of a protective surface ilm passivating the corrosion reaction, and evidence of this was observed. Figure 7 shows the cross-section of the corrosion ilm on a 3% Cr steel (J4a) low-loop tested for 14 days in Forties brine. This ilm was adherent, with uniform thickness (~ 50-100 µm), and few cracks (despite drying at 70 °C before observation by scanning electron microscopy). Energy dispersive X-ray analysis indicated that the ilm was Cr-rich, and also contained V that was an addition to this steel (0.12 wt. (%)).
The stability and mechanism of adsorption of the extract (lignin) on the medium carbonlow alloy steel surface was studied by evaluating the variation of corrosion rate and inhibition efficiency with temperature (303K-333K) (Figures 6-7). It is observed from figure 6 that at any of the temperatures, corrosion rate decreases with increase in lignin extract concentration while the corrosion rates increases with increase in temperature. This trend is consistent with the observations of Okafor et al.  who reported that the tendency for partial desorption of the inhibitor from the metal surface and the metal dissolution increases with temperature. The variation in inhibition efficiency (Figure 7) did not follow a consistent trend like in the case of the corrosion rates. However, inhibition efficiency of the lignin extract ranged between 55.5% - 78.8% for different temperatures.
The reliability of circumferential notched tensile testing for evaluation of fracture toughness was investigated using dual phase medium carbonlow alloy steels produced using two different chemical compositions (A – 0.34C, 0.75Mn, 0.12Cr, 0.13Ni steel and B – 0.3C, 0.97Mn, 0.15Cr steel) and different intercritical treatment procedures. From the results it was observed that despite the samples were not fatigue pre-cracked, the fracture toughness results evaluated from the CNT test were valid (in plain strain condition) and a high correlation between the fracture toughness and notch tensile strength was observed. The fracture toughness values were also found to be in close agreement with data obtained from standard K 1C testing. Dual phase structures produced by utilizing an initial martensitic structure before treating at 770 °C yielded a fine distribution of ferrite and martensite which gave the best combination of tensile properties and fracture toughness for composition A. The dual phase structure produced by treating at 760 °C yielded the best combination of tensile properties and fracture toughness for composition B.
The potential of -0.5 V SCE was chosen to investigate the first passivation region showed in Figure 6. At the applied potential of -0.5 V SCE , the current density remained constant and low with time for the steelsin the cold-rolled condition and showed a slight increasing trend for the steelsin the hot-rolled condition as shown in Figure 8. The cold rolled steels showed the lowest current density in green liquor. The hot rolled S31803 steel showed the highest current density in green liquor, using the potentiostatic test. The cold and hot rolled steels were annealed at 1070 ºC and 1075 ºC, respectively. In the cold rolled steel, the microstructure is finer as shown in Figure 9. The hot-rolled S31803 steel showed a passivation current density one order of magnitude higher (10 -5 A/cm 2 ) than the current of the cold rolled S31803,
The conventional industry, which generates, transmits and makes distribution of energy to be used by our society has established an ample variety of materials that guarantees the success of such a work. Processing oil and utilizing natural gas and their derivatives, for example, has required an important improvement of steels used in fuel production, relative to the corrosion and hydrogen embrittlement resistances and of composite materials for flexible tubes. Steels and special coatings for high temperature work and a variety of catalysts were developed for refineries. Simultaneously, as the oil and gas industry increase their activities on the creation of new materials, it opens an increasing space for special materials used by the companies that produce energy from renewable sources. Much innovation has been presented concerning materials for hydroelectric plant turbines, for wind generators components and to be used in last generation photovoltaic solar cells. But, these are types of fossil and renewable energies in extensive use nowadays and, because of that, they are better known. It's worth to drive the attention of the scientific and business communities to the great creative activity working on the development of materials for the hydrogen energy. In this case, for example, tanks to store gaseous hydrogen under high pressures, of about 700 bar, are needed. High density polymers and carbon fiber based composite materials are expected to guarantee the required mechanical resistance and also gas tightness. Solid oxide fuel cells work at high temperatures, above 650°C, and face the challenge to ensure mechanical compatibility among metallic and ceramic materials in oxidant and reducing environments. Particularly, an important development takes place on ceramic materials with perovskite structure, showing special electrocatalytic properties. This includes the capacity to promote on the anode the direct oxidation of hydrogen and even of more complex fuels, such as biomethane and ethanol, to allow their direct utilization, without previous reforming. And, in addition to that, the ability to promote the efficient reduction of oxygen on the cathode, with an appropriate perovskite. Materia's Editorial Board will be happy to work these themes out on an article of your authorship submitted for publication. Don't hesitate!
The amount, distribution, size and chemical composition of non-metallic inclusions have a direct influence on steel properties. By controlling size and chemical composition of these inclu- sions, it is possible to get a product with good quality. The identification of the nature and the control of inclusion formation are very important for steel cleanness. The behavior of these inclu- sions is predictable, in some extent, by the determination of the chemical composition of non- metallic phases that form such inclusions. With the objective of studying the chemical composi- tion, the size and the distribution of such inclusions, samples of aluminum and silicon killed lowcarbonsteels were collected in a national steel industry in the secondary refining and continuous casting stages. These samples were analyzed in the scanning electron microscope (SEM) coupled to an energy dispersive analysis system (EDS). From the results, it was possible to evaluate the nature of inclusions and to analyze the effectiveness of the refining process in the reduction of the number and area fraction of the inclusions. It was also possible to verify that the inclusions that remained after treatment, are less damage both to the steel properties as to the continuous casting process (clogging of the submerged valve).
Due to the economic losses and environmental damage caused by the deterioration of steel pipes installed under the ground, there is a great incentive to investigate the physicochemical and microbiological characteristics of the soil, showing that microbial groups affect the studied area. Thus, this work was designed to assess the biofilm formation and corrosion of carbon steel coupons API5LX60 for period 15 days in clayey soil samples collected in Pernambuco and used in the Abreu and Lima Refinery. The results were expected to make it possible to set up strategies for monitoring and controlling corrosion.
damaged by the dynamic corrosion effect. Additionally, the coating cracking wear is displayed. Figure 4c, d, it is distinguished a central area characterized by the corrosion action and the cracking of the coating produced by the impact energy of the abrasive particles of silica. Gray areas suggest protective effect has generated defense mechanism with areas of low cracking. By subjecting the surface of the fermanal steels and stainless steels to erosion-corrosion it is notable the modification of the surface for an impact angle of 90° degrees showing faint traces on surface of material. Figure 4b shows the micrographs by formation of localized corrosion which begins to spread over much of the surface. In this case, the eroded surface is very similar to those shown over stainless steel. For AFe2 steel under the action of the marine environment can be seen that the steel surface show areas of generalized corrosion, which has spread across most of the surface, while being subjected the surface to the erosion it is observed a significant damage in the normal angle condition, causing a rough morphology. Both mechanism in synergy, are responsible for a surface with an evident deterioration of material, as in the case of 90° degrees angle where there are traces of mechanical removal of material. The AFe3 steel shows a bigger erosive phenomenon than in the previous cases, it is reflected in a rough surface and slightly texture in the direction of impact of the particles. Also are observing a surface with clear
The discoveries made in the pre-salt are among the world’s most important in the past decade. The pre-salt province comprises large accumulations of excellent quality, high commercial value light oil. A reality that puts Brazil in a strategic position to meet the great global demand for energy (PETROBRAS, 2015).The discovery of the pre-salt layer also brings several technological challenges for the oil and gas exploration below this layer. In 1974 the search of self-sufficiency in the oil industry has become a state policy. Due to the dependence on imported oil and the previous year's price range, Brazil assumed the challenge of the race to the sea, which led Petrobras to explore the little-known Campos Basin (COPPE, 2011). The era of oil can be considered as the second industrial revolution, once that 90% of oil is used for energy purposes, whether in thermoelectric plants, whether as a fuel for means of transport or industrial purposes. From the remaining 10%, the products that supply industries are extracted. Due to the increase of oil consumption, new deposits of oil began to be explored. These new deposits are located at depths that exceed seven thousand meters and have a total capacity of reservoirs capable of reaching 12 billion barrels of oil and natural gas (COPPE, 2011). The oil of these new reservoirs possesses a good quality but in the pre-salt region, the operating environment is very hostile. This fact is due to high temperatures, pressures, presence of corrosive gases such as carbon dioxide (CO 2 ) and hydrogen sulfide
and stability factors of electrolytic baths [11, 12]. De Souza  performed a series of experiments on the use of the ionic liquid of in water at ambient temperature. The electrode plates of these cases were selected from a number of easily found metals such as carbon steel; Nickel; Nickel Molybdenum alloy and Molybdenum. A maximum efficiency value of 96% was reported for the case of lowcarbon steel electrodes  in 10 vol. % aqueous solution of MBI. MF4. All tests took place at the current density value of 44mA cm -2 .
Abstract: Problem statement: The effect of different temperatures and acid concentrations on the corrosion of lowcarbon steel in hydrochloric acid were addressed in this study. Approach: The effect of temperature was explained by application of Arrhenius equation and transition state theory, while the acid concentration effect was explained using reaction kinetic equations. The combined effect of temperature and acid concentration then modeled using a nonlinear regression method. Results: A detail of thermodynamic parameters of activation (E, H * and S * ) and kinetic studies for the corrosion reaction were obtained. Nonlinear corrosion rates as a function of temperature and acid concentration equation were estimated with a good prediction corrosion rates values. Conclusion: The values of activation energy E and enthalpy of activation H * decrease with increase in acid concentration indicating the increasing in reaction rate. Entropy of activation S * tend to lower values with increasing in acid concentration which indicated that the activated complex was more orderly relative to the initial state. The corrosion reaction was approximately firs order reaction. The observed corrosion rate values from the experimental data were in a good agreement with that predicated by the mathematical equation.
Boriding is a thermochemical surface hardening process which occurs with the diffusion of boron atoms on the matrix surface. The introduced boron atoms react with the material and form a number of borides. As a result of these formations, boronizing of the surface of a material allows a significant reduction of the rate of corrosion, oxidation or shaping of fatigue cracks that occur as an outcome of its operation [1-4]. But the main advantage of boronizing metals is the possibility to alloy a high surface hardness with a low friction coefficient. This may lead to good wear resistance. The increase in hardness due to boronizing of steels re-
20%CO and constant flow of 100 cm 3 /min and acetylene variations with flows of 40cm 3 /min, 65cm 3 /min and 85cm 3 /min was used. These gases were injected into the reactor at 900°C and held for three hours. The acety- lene gas was selected as the carbon-enriching agent in the atmosphere, due to the high decomposition ratios of these molecules and the low tendency to develop polymerization reactions. The characterization of the carburized steels was performed by optical microscopy (OM), optical emission spectrometry (OES) and Vickers microhardness tests (HV). The results show that there is a great efficiency and control in the carbon transfer during the carburization cycle, favoring the optimization of resources and processing times.
taining at least 20%Cr generally provide a satisfactory cor- rosion rate of about 0.1 mm/yr or less in the 300-400 °C temperature range at which most heat exchanger surfaces in syngas coolers operate (Fig. 9). Corrosion mechanisms ranged from Type B corrosion for the lower Cr steels to Type A corrosion for steels with a higher Cr content such as 310. When scale spallation due to chloride migration to the scale/metal interface occurs, corrosion rates increase con- siderably even at relatively low temperatures. Figure 10 shows the corrosion loss of the 310 stainless steel of Fig. 8, as a function of time. The rate is linear and is about 0.25 mm/yr. Here a Mo containing alloy such as Sanicro 28 (27Cr, 32Ni, 3.5%, Cu) is a better choice because it has a para- bolic corrosion rate, with less than 0.25 mm loss after 17,000 hr exposure. When the fuel gasified has very high Cl levels extremely high corrosion rates are possible. This is illus- trated in Fig. 11, which gives the results of a 5500 h expo- sure tests in a gasifier using a fuel containing 0.2-0.5% Cl. Here stainless steels have completely unacceptable corro- sion rates and Mo containing alloys, preferably with a high Ni content such as Alloy 625 are the only acceptable mate- rials. It is interesting to note that Alloy 625 is also the pre- ferred alloy for waste to energy plants, where chlorine is the major corrodent under oxidizing conditions 11 .
The presence of Cr and Mo in solid solution enhances hardness, given the presence of carbon. That enhancement explains why the apparent hardness of the chromium-containing steels only increases when carbon diffusion begins. The evolution of apparent hardness with sintering temperature of the studied samples shows that carbon diffusion inlow-alloyed chromium steel begins at 800ºC, and finishes at 1100ºC. In high-alloyed chromium steel, the dissolution of carbon starts at temperatures higher than 1000ºC. The comparison between the three materials underlines the influence of chromium on the hardness of steel. It has to be taken into account that the carbon content of both chromium steels is lower due to the carbothermic reduction processes. The difference in hardness would likely be greater if the carbon content of all the compositions was the same. The influence of chromium and molybdenum on hardness would also be even more important after a thermal treatment that led to a harder microstructure.
The resistance to localised corrosion of the full austenitic 15%Cr-15%Ni-1.2%Mo titanium stabilized stainless steel (DIN W. Nr. 1.4970) was investigated by electrochemical methods including electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and potentiostatic polarization measurements in a phosphate- buffered solution (PBS). The lowcarbon and non-stabilized austenitic stainless steel, AISI 316L (ASTM F-138), widely used for surgical implants, was also tested for comparison. The tests were conducted at room temperature after a stable potential had been reached. After the electrochemical measurements, the surfaces of the specimens were observed using SEM to evaluate the presence of pits. Potentiodynamic polarization results showed that both steels are prone to localized corrosion. Larger pits were found on the surface of AISI 316L specimens after the electrochemical tests. EIS response has indicated the duplex structure of the passive oxides. The results showed that the electrochemical behaviour of the DIN W. Nr. 1.4970 is better than of AISI 316L steel. Therefore, their application as an implant material may be considered.
In this paper, two lowcarbon microalloyed steels, named as steel A and steel B, were fabricated by ultra fast cooling (UFC). In both steels, the microstructures containing quasi polygonal ferrite (QF), acicular ferrite (AF) and granular bainite (GB) can be obtained by UFC process. The amount of AF in steel B is more than that in steel A. The size and distribution of precipitates (Nb/Ti carbonitrides) in steel B are iner and more dispersed than those of in steel A due to relatively low inish cooling temperature. The mechanical properties of both steels are efectively enhanced by UFC process. UFC process produces low-temperature transformation microstructures containing a signiicant amount of AF. The mechanical properties of steel B were more satisfactory than those of steel A due to the iner average grain size, the greater amount of the volume fractions and smaller size of secondary phases.
by sputtering prior to the nitriding step without any damage to the part’s surface. Based on the nitrogen expanded austenite concept, low temperature carburizing has been studied for austenitic and other stainless steels types [Sun, 1999], Michal, 2006]. [Ceschini, 2008], [Souza, 2009]. In such treatments a hard and rather ductile layer increases wear properties and fatigue resistance without impairing the corrosion resistance and even increasing it in some cases. Differently from the Low Tem- perature Plasma Nitriding Treatment of austenitic stainless steels, where up to 35 at% of N can be introduced in austenite in solid solution, leading to the formation of a very hard (1500 HV) nitrogen rich expanded austenite (g N ) layer, Low Tem- perature Plasma Carburizing improves the wear resistance of austenitic stainless steels through the formation of a carbon rich expanded austenite (g C ) containing a maximum of 13 at% C [Cao, 2003], [Mi- chal, 2006] in solid solution, increasing surface hardness up to 1000 HV.
The aim of this study was to evaluate the corrosion resistance of Ni-bearing car- bon steels used in outdoor structures from short-term experimental techniques and compare with the long-term field test data. The carbonsteels studied were two ex- perimental steels, produced in a pilot plant, and alloyed with nickel, copper, silicon and molybdenum (Ni-Cu-Si and Ni-Cu-Mo-Si steels), one carbon steel and one com- mercial Cr-Cu-Si alloyed steel. The atmospheric corrosion resistance of low alloyed carbonsteels was evaluated by using field tests for eight years in a marine station, and their electrochemical behavior was studied in laboratory using the electrochemical im- pedance spectroscopy in aqueous electrolytes containing chlorides. The Ni-Cu-Si and Ni-Cu-Mo-Si steels showed the lowest corrosion rates which decreased as the time increased after eight years of exposure in marine atmosphere. The classification of the low alloyed steels considering the corrosion resistance using electrochemical tests in 10% m/v NaCl solution was similar to rating using field tests in a marine station.