Wyniki wyszukiwania - BazTech

1

Corrosion hampering measurements of AISI 316 SS submerged in alkaline solutions

Hryniewicz T., Kuszczak J.

Pomiary Automatyka Kontrola

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2010

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R. 56, nr 4

344-348

EN

The aim of this study was to investigate the corrosion behaviour of AISI 316 stainless steel to be used as rebars in construction. Austenitic stainless steel AISI 316 samples were put to the alkaline aqueous environments of composition: 0.01M NaOH+0.01M KOH both free of chlorides and those containing 3% NaCl. The hydrogen ion exponent pH was 10 and 12.5. The following electrochemical methods have been used to investigate corrosion: polarization curves PC, Electrochemical Impedance Spectroscopy EIS, and 24-hour open circuit potential OCP studies. The obtained results are quite comprehensive and indicate on faster self-restoration of passive films under action of chlorides. The chlorides do not cause essential changes in the potential values, both corrosion and critical, in comparison with the results on samples studied in the solutions free of chlorides. The studies reveal that, out of two alkaline environments, the AISI 316 SS better performs in the presence of solutions of lower pH. The presence of chlorides in the solution enables faster formation of a passive film and its eventual auto-restoration in case of disruption. The presented investigation results indicate the chlorides accelerate transition of Cr(III) to Cr(VI) on steel surface. The longer steel AISI 316 sample remains in the solution, the more and more film formed on the steel surface strengthens and gets stabilized resulting in better surface protection.

PL

W pracy przedstawiono wyniki badań korozyjnego zachowania się stali kwasoodpornej AISI 316 - przewidywanej do zastosowań konstrukcyjnych w budownictwie - w roztworach alkalicznych. Przygotowane próbki stalowe umieszczono w roztworach o składzie: 0.01M NaOH+0.01M KOH bez chlorków oraz zawierającym 3% NaCl. Wykładnik jonów wodorowych wynosił 10 i 12,5. Do pomiarów korozyjnego zachowania się stali zastosowano badania krzywych polaryzacyjnych PC, elektrochemiczną spektroskopię impedancyjną EIS, oraz badania potencjału obwodu otwartego OCP. Wyniki badań są zgodne i wskazują na szybsze samoodnowienie warstewki pasywnej pod wpływem chlorków. Chlorki nie powodują zasadniczych zmian w wartościach potencjału, i to zarówno korozyjnego jak i krytycznego, w porównaniu z wynikami uzyskanymi w roztworach bez chlorków. Wyniki badań wskazują, że spośród dwu zastosowanych roztworów, stal AISI 316 jest bardziej odporna na korozję w roztworach o niższym pH. Obecność chlorków w roztworze umożliwia szybsze tworzenie się warstewki pasywnej i jej odtwarzanie w przypadku przerwania. Wyniki badań wskazują, że chlorki przyspieszają przejście Cr(III) do Cr(VI) na powierzchni stali. Wydłużenie czasu pozostawania stali w roztworze powoduje umocnienie warstewki i stabilizację ochrony powierzchni stali.

2

The influence of the sintering conditions on the properties of the stainless steel reinforced with TiB2 ceramics

Sulima I., Klimczyk P., Hyjek P.

Archives of Materials Science and Engineering

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2009

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Vol. 39, nr 2

103-106

EN

Purpose: The paper analyzes the influence of the temperature and pressure on the properties and structure of the austenitic AISI 316L stainless steel reinforced with 1% vol.TiB2 ceramics. Design/methodology/approach: The sintered austenitic AISI 316L stainless steel reinforced with 1% vol.TiB2 were obtained using the high temperature-high pressure (HT-HP) method at pressure of 5.0 and 7.5 š 0.2 GPa and temperatures 900°C, 1150°C and 1300°C. The duration of sintering was 60 seconds. Young's modulus measurements were carried out using ultrasonic method. Mechanical properties were determined by Vickers hardness test. For microstructure observation scanning electron microscope JEOL JSM-6460LV was used. Findings: The decrease of the hardness of the sintered austenitic AISI 316L stainless steel with the increasing temperature of sintering was observed. However, the Young's modulus increases with the growth of the temperature of sintering. The results showed that the hardness increased with increasing pressure. The microstructural investigations indicated that the TiB2 ceramics were distributed along grain boundaries. Practical implications: The obtained results show that the temperature and pressure have influence on the mechanical and physical properties of the investigated steel reinforced with 1% vol.TiB2. These results may be used to design new materials i.e. austenitic stainless steel reinforced with TiB2 ceramics. Originality/value: The results from this work can be useful in determining conditions for sintering the austenitic AISI 316L stainless steel reinforced with various volume fractions of TiB2 ceramics.

3

The structure of austenitic steel AISI 316 after ECAP and low-cycle fatigue

Greger M., Vodárek V., Dobrzański L., Kander L., Kocich R., Kuřetová B.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 28, nr 2

151-158

EN

Purpose: The article presents results of investigation of structure and properties of austenitic steel grade AISI 316 after application of Equal Channel Angular Pressing (ECAP) at the temperature of approx. 290° C. Design/methodology/approach: The ECAP method led to significant improvement of strength of investigated material. Experiments were planned and realised at the temperature ranging from room temperature up to above mentioned temperature. Findings: It was established with use of the EBSD technique that after 8 passes through the ECAP die the sub-grains with an angle of disorientation smaller than 10° formed less than 20% of resulting structure. Average size of austenitic grains with high angle boundary after 8 passes was approx. 0.32 µm. It was proven that the ECAP method enables obtaining of ultra fine-grained austenitic structure formed by recrystallised grains with very low density of dislocations. Practical implications: The Technology ECAP was applied on austenitic steel AISI 316. It was verification of ECAP application possibility on steel AISI 316 importantly for following applying on similar kinds of steel, because ECAP technology influence on fatigue properties was confirmed. Originality/value: It can be predicted on the basis of obtained results that, contrary to low-cycle fatigue the ultra-fine grained material will manifest at fatigue load in the mode of constant amplitude of stress higher fatigue characteristics, particularly fatigue limit.

4

Structure and low-cycle fatigue of steel AISI 316 after ECAP

Greger M., Kander L., Kocich R.

Archives of Materials Science and Engineering

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2008

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Vol. 31, nr 1

41-44

EN

Purpose: Main aim of this paper is to describe the plastic deformation executed by ECAP on low cycle fatigue of steel AISI 316. Among others was attention fixed on mechanical properties after this treatment. Design/methodology/approach: Experiments were planned and realised at the temperature ranging from room temperature up to 280 °C. After application of deformation the structure was investigated in dependence on accumulation of deformation and deformation temperature as well as abovementioned final properties. Findings: Accumulated real (logarithmic) deformation varied from the value 2 to 8. Investigation of structure by electron microscopy was made with use of microscope JEOL JEM 2100. Mechanical properties were investigated by conventional tensile test and penetration test. Selected samples were subjected to low-cycle fatigue. Statistic evaluation of angular disorientation and of size of grains/sub-grains was also made with use of electron diffraction (EBSD) in combination with scanning electron microscope FEG SEM Philips. Practical implications: The Technology ECAP was applied on austenitic steel AISI 316. It was verification of ECAP application possibility on steel AISI 316 importantly for following applying on similar kinds of steel, because ECap technology influence on fatigue properties was confirmed. Originality/value: It can be predicted on the basis of obtained results that, contrary to low-cycle fatigue the ultra-fine grained material will manifest at fatigue load in the mode of constant amplitude of stress higher fatigue characteristics, particularly fatigue limit.