جستجوی مقالات مرتبط با کلیدواژه "رفتار خوردگی" در نشریات گروه "مکانیک"

In the present study, in addition to reviewing the severe plastic deformation (SPD) processes and their mechanisms in the microstructural evolution, previous researches on the corrosion behavior of various metallic materials that have undergone SPD are investigated. Grain size, as an important metallurgical parameter, affects a broad range of mechanical, chemical, physical and electrochemical properties of metallic materials. As mostly reported, the reduction in grain size is in line with a considerable improvement in the mentioned properties. In recent years, SPD methods have been nominated as an ideal way to reach nano- and ultrafine-grains. Among the mentioned properties, the corrosion performance of ultrafine-grained materials produced by SPD methods is still controversial for researchers. The purpose of this study is to review the SPD methods, the mechanism of grain refinement during them, and their effects on the corrosion behavior of various metals and engineering alloys such as steels, aluminum, titanium, copper, and magnesium.

In this study, the effect of austempering process on the metallurgical transformations and corrosion behavior of weld metal in Hadfield manganese steel welding joints was investigated. For this 4 purpose, initially austenitized sheets with thickness 2mm prepared from Hadfield steel and then SMAW process was used for welding. Then one joint remains in welded condition and other joint were austempered at temperature 1000°C for one hour. Evaluation of the microstructures was conducted by optical microscopy. X-ray diffraction was used for the analysis of phases formed in the microstructure. For evaluation of weld metal corrosion behavior, potentiodynamic polarization and electrochemical impedance spectroscopy methods were used in the 3.5% NaCl solution. The results showed that with austempering treatment, increased corrosion resistance of the weld metal. Because the effect of austempering process, corrosion aggravating factors (amount of sediments and the number of grain boundaries) decreased in the welding joints weld metal.

In the present study, two inhibitors, benzomidazole and methyl benzomidazole, were used to prevent corrosion of X70 micro-alloy steel in acidic environment in one molar of sulfuric acid. For this purpose, both inhibitors in different concentrations were investigated in order to find the best concentration, temperature and efficiency of weight loss tests, polarization and electrochemical impedance spectroscopy (EIS). The chemical composition of the sample was obtained by quantum test and the sample with dimensions of 100 × 50 × 10 mm was prepared in 20 pieces. Corrosion protection performance of inhibitors in 1 M sulfuric acid solution for weight loss test after 10 days of immersion and also in polarization and impedance tests using Auto Lab and Nova1.11 software were evaluated. . As a result, the best inhibitory efficiency of benzomidazole at a concentration of 600 ppm was equal to 37% and methyl benzomidazole at a concentration of 400 ppm equal to 30%, and in the combined state of these two solutions have the ability to increase corrosion efficiency up to 73%. As a result, both of these inhibitors showed practical ability to be used in industrial environments.

In this study, the effect of Al on the corrosion resistance of Hadfield steel weld joints’ fusion zone was investigated. For this purpose, 4 austenitized sheets (two sheets without Al and two sheets containing 1.7wt. %Al) with thickness 2mm prepared from Hadfield steel and then SMAW process was used for welding. Then potentiodynamic polarization and electrochemical impedance spectroscopy methods were used to evaluate corrosion behavior of welded joints’ fusion zone in the 3.5wt. %NaCl solution. The evaluation of the microstructures of weld metal in welding joints were conducted by optical microscopy and the corrosion mechanism were determined by scanning electron microscopy examination. The result of corrosion tests indicated that welded joints’ fusion zone of Al containing plates were more corrosion resistant. Because Al addition increased the solubility of carbon in austenite phase and as a result factors enhancing localized micro-galvanic corrosion such as grain boundaries and carbides were reduced. However as clearly was visible in scanning electron microscopy images, using joints design containing Al in comparison with joints design without Al led to changed weld metal corrosion mechanism from uniform corrosion to localized micro-galvanic corrosion in the Hadfield steel weld joints.

Equal channel angular rolling process (ECAR) is one of the newest processes in the severe plastic deformation methods (SPD) that changes the mechanical properties of the sheet metal. In this study, the effects of ECAR process have been investigated on the corrosion behavior of the pure commercial copper samples. Five routs have been applied on the samples to investigate the mentioned parameters. Also, the corrosion rates were examined by the polarization and electrochemical impedance methods. The results show that the process has destructive effect on corrosion resistance of the samples. The results from SEM examination indicates that, with increasing the number of passes, the surface corrosion increases too and with increasing the passes pitting corrosion is clearly visible. Although with increasing the number of passes the uniformity of corrosion can be seen and positional mode is exited. Generally, the corrosion increases from the first pass to the second pass. Also, the more diameter and depth of corrosion is observed with increasing the pass number. The corrosion increase at the third pass and the corrosion type is pitting corrosion and uniform corrosion in the sample.

The excellent properties of super duplex stainless steels (SDSS) are mainly due to their balance of ferrite - austenite since this balance is highly likely to change during welding and undesirable phases can create. In this work gas tungsten arc welding (GTAW) process was used to join UNS S32750 SDSS to API X65 high strength low alloy (HSLA) steel. The properties of weldments were investigated by impact test, potentiodunamic and cyclic polarization tests. Zero resistance ammeter (ZRA) tests also were used for investigation of behavior of galvanic corrosion on weld metal – HSLA base metal. Results indicated that amount of austenite in weld metal was higher than SDSS base metal and did not created undesirable phases. Toughness of weldment was higher than base metals and corrosion behavior of weld metal was alike SDSS base metal and presented excellent corrosion resistance comparing HSLA base metal. The results of ZRA showed that HSLA eroded in galvanic couple weld metal – HSLA and mechanism of corrosion was pitting corrosion.