Wyniki wyszukiwania - BazTech

1

Influence of primary silicon precipitates on anodized aluminum alloys surface layer properties

Labisz K., Konieczny J., Wierzbicki Ł., Ćwiek J., Butor A.

Transport Problems

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2018

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T. 13, z. 2

111--120

EN

In this work, we presented the influence of the anodizing method and parameters, as well as the chemical composition of the used aluminium alloys on the properties and microstructure of the anodic layer produced on aluminium alloys, in particular on the size and morphology of the primary silicon precipitates and the homogeneity of the resulting oxide coating. Aluminium alloys AlSi8 and AlSi12, produced using the die-casting method and subsequently subjected to anodic oxidation were used as test material. The microstructure of the obtained surface layer was analyzed by taking into account the primary silicon precipitates. The results of the hardness and abrasive wear test also show the influence of anodizing and electrolyte parameters on the structure and properties of the tested aluminium alloys.

2

IoT - Internet Rzeczy jako narzędzie pomiaru komfortu i zapewnienia bezpieczeństwa w środkach transportu publicznego

Ćwiek J., Błach M., Dacy S., Jakubczyk J., Jarczyk W., Mańka A., Oleksik M.

Komunikacja Publiczna

|

2018

|

nr 3

23--29

PL

Artykuł opisuje doświadczenie przeprowadzone przez zespół studentów Wydziału Transportu Politechniki Śląskiej, przy wsparciu merytorycznym kadry Katedry Transportu Kolejowego Wydziału Transportu, związane z wykorzystaniem autorskiego oprzyrządowania pomiarowego opartego o mikrokontroler i specjalnie opracowane oprogramowanie. W ramach realizacji projektu wykonano prototyp urządzenia, a następnie wykonano pomiary wilgotności względnej oraz temperatury powietrza wewnątrz pojazdów i natężenia światła podczas przejazdu. Następnie wyniki badań zostały poddane analizie oraz zestawione z wymaganiami normowymi dla różnych środków transportu.

EN

The paper describes experiments, related to the use of proprietary measuring instruments based on a microcontroller and on specially developed software, carried out by a team of students from the Faculty of Transport of the Silesian University of Technology with the subject-matter support of the staff of the Department of Rail Transport, Faculty of Transport. Under the project implementation a prototype of instrument was made and then measurements of relative humidity and of air temperature inside vehicles and of the light intensity during travelling were made. The results of studies were then analysed and compared with requirements of standards for various means of transport.

3

Application of isothermal heat treatment for perlite rail-steel

Dopierała K., Ćwiek J., Labisz K., Konieczny R.

Inżynieria Materiałowa

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2017

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Vol. 38, nr 2

82--87

EN

Rail steel production consists of proper combination of alloying elements and heat treatment, where a wide range of grades can be produced, differing in terms of hardness and the corresponding resistance to wear. A railway’s choice of rail grade is made in terms of traffic and track conditions and excellent service life can be achieved, particularly if modern rail head lubrication and grinding practices are used. This investigations deal with changing the standard heat treatment, based on classic perlitic steel to save energy during the production. For this reason the investigated R350HT steel was subjected to isothermal heat treatment, consisting of hardening to obtain bainitic microstructure. The steel was then annealed, after this step a further cooling took place with furnace then final cooling have been made in air. The microstructure of the steel was examined in the light metallographic microscope Zeiss and scanning electron microscope. In addition, on samples cross-section Vicker's microhardness examination was performed as well as friction wear test was carried out with the use of a tribometer. Also Charpy impact toughness test was performed at room temperature for evaluation of the obtained mechanical properties. On the basis of the carried out analysis of the light microscope structure investigations, it was found, that the microstructure of the R350B steel was formed of relative large irregular grains. The obtained results of the mechanical properties investigations reveals only a low increase of the hardness, wear resistance of the 350B steel compared to the classical 350HT steel. The obtained results have not confirmed the occurrence of the bainitic structure in the 350B steel, however the present ferritic structure reveals some advantage related mainly to lower energy consumption during heat treatment with a hardness and wear resistance values nearly on the same level as in case of the 350HT steel.

PL

Stawiane obecnie wymagania dotyczący szyn kolejowych są coraz bardziej restrykcyjne i obejmują coraz więcej wcześniej nie uwzględnianych parametrów. Wraz ze zwiększającymi się wymaganiami idzie potrzeba usprawniania procesu technologicznego obejmującego szereg etapów, takich jak: ciągłe odlewanie stali, walcowanie, obróbka cieplna i prostowanie. Konieczne jest opracowywanie nowych gatunków stali o lepszych właściwościach, w szczególności odporności na wady kontaktowo zmęczeniowe. Największe możliwości sterowania właściwościami stali stosowanych na szyny daje modyfikacja mikrostruktury z perlitycznej na bainityczną. Celem podjętej pracy było uzyskanie w stali szynowej o składzie chemicznym odpowiadającym gatunkowi R350HT struktury bainitu, a następnie porównanie twardości i odporności na ścieranie oraz struktury stali zahartowanej ze stalą w stanie przed obróbką izotermiczną (struktura perlityczna). W skład badanego materiału wykorzystanego do produkcji stali szynowej wchodziły odpowiednio dobrane dodatki stopowe oraz została zastosowana określona obróbka cieplna. Istnieje wiele gatunków stali szynowych różniących się twardością i odpornością na zużycie ścierne. Dobór stali odbywa się pod kątem warunków eksploatacyjnych torów, a odpowiednią trwałość można osiągnąć, zapewniając otrzymanie wymaganej mikrostruktury, odpowiednie smarowanie oraz wyszlifowanie powierzchni. Badania dotyczyły w szczególności modyfikacji standardowej obróbki cieplnej stosowanej dla klasycznej stali bainitycznej w celu zmniejszenia energochłonności procesu produkcyjnego.

4

Microstructure of Archaeological 17th Century Cast Copper Alloys

Konieczny J., Labisz K., Głowik-Łazarczyk K., Ćwiek J., Wierzbicki Ł.

Archives of Foundry Engineering

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2017

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Vol. 17, iss. 2

190--196

EN

In Poland, researchers have a very strong interest in archaeometallurgy, which, as presented in classical works, focuses on dating artefacts from the prehistoric and early medieval periods in the form of cast iron and copper castings. This study, extending the current knowledge, presents the results of a microstructure investigation into the findings from the Modern era dating back to the late Middle Ages. The investigated material was an object in the form of a heavy solid copper block weighing several kilograms that was excavated by a team of Polish archaeologists working under the direction of Ms Iwona Młodkowska-Przepiórowska during works on the marketplace in the city of Czestochowa during the summer of 2009. Pre-dating of the material indicates the period of the seventeenth century AD. The solid copper block was delivered in the form of a part shaped like a bell, named later in this work as a “kettlebell”. To determine the microstructure, the structural components, chemical composition, and homogeneity, as well as additives and impurities, investigations were carried out using light microscopy, scanning electron microscopy including analysis of the chemical composition performed in micro-areas, and qualitative X-ray phase analysis in order to investigate the phase composition. Interpretation of the analytical results of the material’s microstructure will also help modify and/or develop new methodological assumptions to investigate further archaeometallurgical exhibits, throwing new light on and expanding the area of knowledge of the use and processing of seventeenth-century metallic materials.

5

Microstructure and properties evaluation of rail-steel after isothermic heat treatment

Dopierała K., Ćwiek J., Labisz K.

Modelowanie Inżynierskie

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2016

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T. 27, nr 58

18--23

EN

The material used for the production of a rail steel is composed of an appropriate combination of alloying elements and requires a particular heat treatment. There is a wide range of grades of steel, differing in terms of hardness and wear resistance; appropriate selection is done for operating conditions of the track, the durability can be achieved by providing obtain the desired microstructure, lubrication and sanding surface. This study on the changes of the standard heat treatment applied to either bainitic steel in order to reduce the energy needed for production purposes.

PL

Materiał wykorzystywany do produkcji stali szynowej składa się z odpowiedniej kombinacji dodatków stopowych oraz wymaga zastosowania określonej obróbki cieplnej. Istnieje szeroki zakres gatunków tych stali różniących się pod względem twardości i odporności na zużycie ścierne; odpowiedni dobór odbywa się pod kątem warunków eksploatacyjnych torów, odpowiednią trwałość można osiągnąć, zapewniając otrzymanie wymaganej mikrostruktury, odpowiednie smarowanie oraz wyszlifowanie powierzchni. Niniejsze badania dotyczą zmiany standardowej obróbce cieplnej, stosowanej dla klasycznej stali bainitycznej w celu zmniejszenia energii koniecznej dla celów produkcyjnych.

6

The use of technology of spatial printing in designing the PZL-10W engine model

Kowalski M., Kotlarz W., Zahorski T., Ćwiek J.

Journal of Polish CIMEEAC

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2016

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Vol. 11, no 1

103--110

EN

The aim of this paper is to present the possibilities of using 3D spatial printing technology to create complex models, e.g. turbine helicopter engines, PZL-10W type, operated on the W-3 “Sokół” helicopter. We have presented the process of creating a spatial model using CAD software. It required a careful selection of the parts necessary for its manufacture as well as elimination of minor parts, which were insignificant from the functional and educational perspective of the model. We presented the type of printer which was used to prepare the model, and also its software. The verification of the correctness of designing the files for particular parts was made with Netfabb software. Proper verification affected the choice of files to be sent to the 3D printer software, where they underwent further slight changes concerning, among others, the thickness of the layers and the percentage of filling the interior of the individual parts of the engine. The printouts of the selected engine parts have been shown in the photographs. We also (briefly) described the processes of treatment of the parts, their labour intensity as well as the hardware used on a regular basis for this purpose. Finally, we discussed the assembly process of the entire engine. In conclusion, we stressed the importance of the model as a significant didactic aid which is to support the process of acquiring knowledge related to the construction, kinematics and operation of the turbine engine. We also specified the amount of used materials, labour consumption (in man-hours) with regard to the same printout of the parts as well as the finishing works.

7

Odporność wybranych powłok ochronnych na korozję płomieniową w kotłach pyłowych niskoemisyjnych

Ćwiek J., Łabanowski J., Sozańska M., Topolska S.

Rynek Energii

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2013

|

Nr 2

61--64

PL

W artykule omówiono zagadnienie odporności powłok na rurach ekranowych kotłów niskoemisyjnych na korozję płomieniową. Przedstawiono wyniki badań diagnostycznych powłok ochronnych na rurach ekranowych kotłów pyłowych, niskoemisyjnych, pracujących przy współspalaniu biomasy. Badano powłoki natryskiwane cieplnie Al2O3/Ni-30Cr oraz hybrydowe nanoszone techniką malarską. Stan powłok oceniono po jednym i dwóch latach eksploatacji w warunkach oddziaływania płomienia i spalin, oraz erozyjnego oddziaływania strumienia powietrza ze zdmuchiwacza. Stwierdzono, że badane powłoki ochronne nie zabezpieczają powierzchni rur ekranowych przed korozją płomieniową, w tym siarkową, w warunkach spalania podstechiometrycznego. Współspalanie biomasy znacząco przyśpiesza degradację powłok, szczególnie hybrydowych nanoszonych techniką malarską. Trwałość powłok wynosiła do dwóch lat eksploatacji kotła.

EN

Diagnostic research on durability of protection coatings on water-wall tubes in low-emission boilers has been presented in the paper. Thermal spraying Al2O3/Ni-30Cr and hybrid paint coatings were evaluated. Durability of the coatings was evaluated after one and two years of service in direct action of flame, flue gas, and air flux from blower. It has been said that the coatings do not protect heating surface of water-wall tubes from hot corrosion, including sulfidation under substoichiometric burning. Durability of the coatings is two years of exploitation of a boiler.

8

Ocena trwałości powłok ochronnych na rurach ekranowych kotłów niskoemisyjnych

Ćwiek J.

Ochrona przed Korozją

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2012

|

nr 4

172-175

PL

W artykule przedstawiono wyniki badań diagnostycznych powłok ochronnych pracujących na rurach ekranowych w kotłach pyłowych niskoemisyjnych. Badano powłoki natryskiwane cieplnie Al2O3/Ni-30Cr oraz hybrydowe nanoszone techniką malarską. Oceniono trwałość powłok po jednym i dwóch latach eksploatacji w warunkach bezpośredniego oddziaływania płomienia i spalin, oraz erozyjnego oddziaływania strumienia powietrza ze zdmuchiwacza. Stwierdzono, że badane powłoki ochronne nie zabezpieczają powierzchni ogrzewanej rur ekranowych przed korozją płomieniową, w tym siarkową, w warunkach spalania podstechiometrycznego. Trwałość powłok wynosi od jednego do dwóch lat eksploatacji kotła.

EN

Diagnostic research on durability of protection coatings on water-wall tubes in low-emission boilers has been presented in the paper. Thermal spraying Al2O3/Ni-30Cr and hybrid paint coatings were evaluated. Durability of the coatings was evaluated after one and two years of service in direct action of fl ame, fl ue gas, and air flux from blower. It has been said that the coatings do not protect heating surface of waterwall tubes from hot corrosion, including sulfi dation under substoichiometric burning. Durability of the coatings is from one to two years of exploitation of a boiler only.

9

Ocena trwałości rur ekranowych z powłokami ochronnymi eksploatowanych w kotłach niskoemisyjnych

Ćwiek J., Łapanowski J., Sozańska M.

Energetyka

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2012

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nr 11

660-663

PL

Badania diagnostyczne powłok ochronnych - natryskiwanej cieplnie AI203/Ni-30Cr oraz hybrydowej nanoszonej techniką malarską - pracujących na rurach ekranowych w kotlach pyłowych niskoemisyjnych dowodzą m. in., że powłoki ochronne nie zabezpieczają powierzchni ogrzewanej rur ekranowych przed korozją plomieniową; dodatkową przyczyną niskiej trwałości powłok jest duże stężenie siarki i chloru w węglu oraz współspalanie biomasy.

EN

Diagnostic tests of protective coatings - the thermal sprayed AI203/Ni-30Cr and the hybrid one laid with the use of painting technology - working on waterwall tubes in low-emission pulverised fuel boilers prove, among the others, that protective coatings do not secure the heating surface of waterwall tubes from flame corrosion. The additional cause of the short life of coatings is a high sulphur and chlorine content in coal as well as co-combustion of biomass.

10

Durability evaluation of protection coatings on water-wall tubes of low-emission boilers

Ćwiek J.

Archives of Materials Science and Engineering

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2012

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Vol. 56, nr 2

69--74

EN

Purpose: of the paper is presentation of diagnostic research on durability of protection coatings on water-wall tubes in low-emission boilers. Design/methodology/approach: Thermal spraying Al2O3/Ni-30Cr and hybrid paint coatings were evaluated. Durability of the coatings was evaluated after one and two years of service in direct action of flame, flue gas, and air flux from a blower. For evaluation of a level of degradation examinations of chemical composition and morphology of coatings and scales have been performed with the use of scanning electron microscope (SEM) equipped with EDS (energy dispersion X-ray spectroscopy) spectrometer. Findings: Ceramic Al2O3/Ni-30Cr coatings are resistant to flame corrosion, but failed due to cracks generated by thermal stresses. Hybrid paint coatings do not protect steel tubes against hot corrosion (flame corrosion) since oxygen, sulphur and chlorine can easily diffuse throughout the coating. Resulting sulphide scale under the coating causes spalling of the coating. Sulfidation attack results in accelerated corrosion (wastage rate). Research limitations/implications: Initial state of the coatings, and chemistry of combustion atmosphere have not been exactly known. Practical implications: Generation of NOx is limiting by firing fuel with lower amount of oxygen than required for complete combustion, i.e. under sub-stoichiometric conditions. Under these conditions carbon and sulfur present in coal are released as CO and H2S gases. Additionally, unburned carbon particles arrive at water walls, which lead to high temperature oxidation, sulfidation and sometimes molten salt attack. Sulfidation mechanism results in accelerated corrosion rate, and additional costs due to unscheduled outages and replacement of water-wall tubes. Originality/value: It has been found that the coatings do not protect heating surface of water-wall tubes from hot corrosion, including sulfidation under sub-stoichiometric burning. Durability of the coatings is from one to two years of exploitation of a boiler only.

11

Wpływ wodoru na warstwy azotowane na stali 34CrAlNi7-10

Ćwiek J.

Ochrona przed Korozją

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2011

|

nr 4-5

225-229

PL

W artykule przedstawiono wyniki badań wpływu warstwy azotowanej jarzeniowo na stali 34CrAlNi7-10 na jej podatność na niszczenie wodorowe. Badania przeprowadzono rozciągając próbki z małą prędkością w powietrzu i środowisku kwaśnym podczas polaryzacji katodowej. Badano przenikanie oraz absorpcję wodoru przez warstwę azotowaną - wykonano elektrochemiczne pomiary przenikania wodoru przez membranę oraz pomiary ekstrakcji próżniowej. Przełomy próbek po próbach rozciągania obserwowano przy użyciu skaningowego mikroskopu elektronowego w celu określenia wpływu wodoru na zmianę charakteru pękania. Warstwy azotowane stanowią barierę dla wnikania wodoru do stali, przez co zmniejsza się jej podatność na niszczenie wodorowe. Wodór jest głównie akumulowany w strefie azotków. Nawodorowanie warstwy azotowanej nie powoduje zwiększenia jej kruchości w próbie odkształcania z małą prędkością.

EN

Studies on the influence of nitrided layer on 34CrAlNi7-10 on the susceptibility of steel to hydrogen degradation has been presented in the paper. Investigations were carried out using the slow strain tensile rate test (SSRT) in air and in an acidic environment under cathodic polarization. Permeation and absorption of hydrogen in nitrided layer were evaluated - an electrochemical hydrogen permeation test through a membrane, and hydrogen vacuum extraction test were performed. The fractured surface of the specimens with modified layers were examined using a scanning electron microscope (SEM) in order to determine the influence of hydrogen on change in the fracture mode. Plasma nitrided layers, being effective barriers to hydrogen entry into steel, decrease the susceptibility of steel to hydrogen degradation. Hydrogen is mainly accumulated in a compound nitrides zone. There is no evidences for increase in the brittleness of nitrided layers with absorbed hydrogen.

12

Interaction between hydrogen and a nitrided layer

Ćwiek J.

Journal of Achievements in Materials and Manufacturing Engineering

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2011

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Vol. 47, nr 1

34--41

EN

Purpose: of this paper is to reveal the influence of nitrided layer on 34CrAlNi7-10 steel to its susceptibility to hydrogen degradation. Investigation was carried out with the use of slow strain tensile rate test (SSRT). Design/methodology/approach: Nitriding was done in the nitrogen-hydrogen (or argon) gas atmospheres with various hydrogen content, i. e. 0%, 30%, and 70%, at the glow discharge at temperature 560°C for 6 hrs. In order to estimate the degree of hydrogen degradation SSRT test was conducted on round smooth specimens 4 mm in diameter. Tests were performed at ambient temperature either in dry air or in 0.005 M H2SO4 solution. The applied strain rate was 10-6 s-1. Tests in acid solution were conducted under cathodic polarization with constant current densities: 0.1; 1; 5 and 10 mA/cm2. Fracture surfaces after SSRT test were examined with scanning electron microscope (SEM) to reveal a mode and mechanism of cracking. Findings: Plasma nitrided layers are effective barriers to hydrogen entry into structural steel which decreases susceptibility of steel to hydrogen degradation. Hydrogen is mainly accumulated in a compact nitrides zone. Evidences of no increase in brittleness of nitrided layers with absorbed hydrogen were observed. Research limitations/implications: There is no possibility to perform direct observations of exact mechanism of hydrogen-assisted cracking so far. Further research should be taken to reveal the exact mechanism of increased plasticity of nitrided layer with absorbed hydrogen. Practical implications: Plasma nitrided layers are effective barriers to hydrogen entry into structural steel utilized in aggressive environments, which could be potential sources of hydrogen charging of exploited steels. Originality/value: Plasma assisted nitriding provides the formation of thin compact nitride zone which protects high-strength steels against corrosion and hydrogen degradation. Evidences of no increase in brittleness of nitrided layers with absorbed hydrogen were observed.

13

Evaluation of microstructure and mechanical properties of a steam turbine casing after long-term service

Ćwiek J.

Journal of Achievements in Materials and Manufacturing Engineering

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2011

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Vol. 49, nr 1

27--34

EN

Purpose: of this paper is to reveal the microstructural changes in Cr-Mo and Cr-Mo-V cast steels steel exposed to long-term service at elevated temperatures. The paper presents results of research and failure analysis undertaken to determine failure causes of a steam turbine casing. After 130,000 hours of service the crack in a outer shell of the turbine casing was found. Design/methodology/approach: Following research were performed in order to determine causes of the casing failure: chemical analysis; microstructure examinations with the use of light microscope, scanning electron microscope (SEM); transmission electron microscopy (TEM); mechanical properties examinations using the Charpy impact test, and Vickers hardness test; fracture mode evaluation with SEM; the energy dispersive X-ray spectrometry (EDS). Findings: The cracking of the outer casing occurred due to various causes. The main cause was stress distribution and stress changes during service of the turbine. The microstructure of ferrite and bainite/perlite is more susceptible to cracking than tempered martensite. Carbides coagulation process occurs at ferrite grain boundaries which increased embrittlement. Big nonmetallic inclusions also contribute to brittleness of material. Research limitations/implications: The whole history of start-ups and shutdowns of the turbine during long term service has not been recorded. There was no possibility to take samples with fracture area. Thus, service conditions of investigated samples and material of cracking area were different. Practical implications: Useability of the method for assessing the current degradation based on analysis of carbides morphology was confirmed for Cr-Mo and Cr-Mo-V cast steels. Originality/value: Microstructure composed of ferrite and perlite/bainite is more liable for degradation processes, during long-term exploitation at elevated temperature, than microstructure of tempered martensite.

14

The effect of long-term service at elevated temperatures on structure and mechanical properties of Cr-Mo-V steel

Ćwiek J., Łabanowski J., Topolska S.

Archives of Materials Science and Engineering

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2011

|

Vol. 49, nr 1

33-39

EN

Purpose: of this paper is to reveal the microstructural changes in 13HMF steel exposed to long-term service at elevated temperatures. The degradation of bainite structure was determined and carbides morphology has been examined. The influence of carbides evolution was discussed in dependence of creep rupture strength and mechanical properties of the steel. Design/methodology/approach: Examinations were conducted on 273 mm diameter, 32 mm wall thickness tube made of 13HMF (14MoV6-3) steel. The tube was a segment of stem pipeline used in power plant at 540°C. The service time is 168,000 hours. Microstructure of the material has been examined with the use of light optical microscopy and scanning electron microscopy (SEM). The energy dispersive X-ray spectrometry (EDS) analysis was used for phase chemical composition identification. Transmission electron microscopy (TEM) of thin foils was used for carbides structure identification. The mechanical properties of the tube material were evaluated in static tensile tests at room temperature, hardness tests and impact Charpy U tests. Findings: Microstructure of 13HMF steel tube shows an advanced level of degradation - coagulation of carbides at ferrite grain boundaries and inside bainitic grains. Precipitates of carbides decorated grain boundaries in chain forms. The presence of M7C3, M23C6, M6C phases were revealed. After extended service M23C6 and M3C carbides were replaced by more stable carbides. This transformation did not occur until the end. This indicates the presence of mainly Mo2C carbide, and only sporadic occurrence of carbide M6C. Practical implications: Useability of the method for assessing the current degradation level and for predicting residual lifetime of creep-resistant tubes based on analysis of carbides morphology was confirmed for Cr-Mo-V steel. Originality/value: Information available in literature does not clearly indicate the influence of microstructure and mechanical properties of Cr-Mo-V steel after long-term exploitation. The study shows such relations.

15

Prevention methods against hydrogen degradation of steel

Ćwiek J.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 43, nr 1

214-221

EN

Purpose: of this paper is presentation of mechanisms and forms of hydrogen degradation in steel along with pointing out methods for hydrogen degradation prevention. Design/methodology/approach: Hydrogen degradation of steel is a form of environmentally assisted failure which is caused by the action of hydrogen often in combination with residual or applied stress resulting in reduction of plasticity, load bearing capacity of a component, and cracking. Findings: The sources of hydrogen in steel were presented. Forms of hydrogen presence in metals, mechanisms of hydrogen degradation, and types of hydrogen induced damage were discussed in details. Five specific types of hydrogen induced damage to metals and alloys could be distinguished: hydrogen embrittlement, hydrogen-induced blistering, cracking from precipitation of internal hydrogen, hydrogen attack, cracking from hydride formation. Practical implications: Methods for hydrogen degradation prevention include: selection of suitable material, modifying environment to reduce hydrogen charging, and use of surface coatings and effective inhibitors. Originality/value: Originality the paper outlines the problem of hydrogen degradation of steel and other alloys, delivering knowledge to undertake preventive or remedial actions in order to avoid hydrogen induced degradation.

16

Evaluation of hydrogen degradation of high-strength weldable steels

Ćwiek J., Michalska-Ćwiek J.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 42, nr 1-2

103-110

EN

Purpose: of this paper is evaluation of susceptibility of a high-strength steel and welded joints to hydrogen degradation and establishing of applicable mechanism of their hydrogen embrittlement and hydrogen delayed cracking. Design/methodology/approach: High-strength quenched and tempered steel grade S690Q and its welded joints have been used. Susceptibility to hydrogen embrittlement of steel and welded joints has been evaluated using monotonically increasing load. Slow strain rate test (SSRT) was carried out in hydrogen generating environment, i.e. artificial sea water under cathodic polarization. Susceptibility to hydrogen delayed cracking has been evaluated under constant load in artificial sea water under cathodic polarization. Fractographic examinations with the use of scanning electron microscope (SEM) were performed to establish suitable mechanism of hydrogen-enhanced cracking. Findings: Tested high-strength steels and its welded joints are susceptible to hydrogen embrittlement when evaluated with the use of SSRT. The loss of plasticity is higher for welded joints then for the base metal. Tested steels and welded joints reveal high resistance to hydrogen degradation under constant load. Research limitations/implications: Further research should be taken to reveal the exact mechanism of crack initiation. Practical implications: Tested steel and its welded joints could be safely utilized in marine constructions under cathodic protection provided that overprotection does not take place. Tested steel could be safely utilized within elastic range of stress in hydrogen generating environments. Originality/value: Hydrogen-enhanced localized plasticity (HELP) model is more applicable mechanism of hydrogen degradation for tested steel and its welded joints under monotonically increasing load in seawater environment. Under the critical load and hydrogen concentration notched samples premature failed and hydrogen-enhanced localised plasticity (HELP) model is a viable degradation mechanism.

17

Behaviour of nitrided layers subjected to influence of hydrogen

Ćwiek J., Baczyńska M.

Archives of Materials Science and Engineering

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2010

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Vol. 43, nr 1

30-41

EN

Purpose: of this paper is evaluation of behaviour of plasma nitrided layers subjected to influence of internal and external hydrogen. Properties of nitrided layers like: hydrogen permeation and trapping, fracture mode, and plasticity were examined. Design/methodology/approach: Structural low-alloy steel was nitrided at glow discharge in the gas mixture of various N2, H2, and Ar content. Samples with nitrided layers were subjected to cathodic hydrogen charging in acid solution simulating the aged engine oil hydrogenating environment. The effect of the nitrided layers on the hydrogen transport and on the irreversible trapping was evaluated by the measurements of the hydrogen permeation rate and by the vacuum extraction, respectively. Surfaces with modified layers were examined with the use of a scanning electron microscope (SEM) before and after hydrogen permeation tests. Slow strain rate test (SSRT) on samples with and without nitrided layers was carried out in hydrogen generating environment. After SSRT fracture mode and plasticity of nitrided layers were examined with SEM. Findings: In the presence of the not defected compact nitride layer, no hydrogen permeation through the steel has been stated under the experimental conditions. Influence of hydrogen content in working atmosphere, i.e. internal hydrogen, was found. Absorbed hydrogen, i.e. external hydrogen, was accumulated within this layer. Research limitations/implications: There is no possibility to perform direct observations of exact mechanism of hydrogen-assisted cracking so far. Further research should be taken to reveal the exact mechanism of increased plasticity of nitrided layer with absorbed hydrogen. Practical implications: Plasma nitrided layers are effective barriers to hydrogen entry into structural steel utilised in aggressive environments, which is especially important in the case of possible hydrogen charging of exploited steel. Originality/value: Using the atmosphere of the higher nitrogen to hydrogen ratio at plasma assisted nitriding provides the formation of thin compact nitride zone, highly protective against corrosion and hydrogen degradation. Evidences of a likely increased plasticity of nitrided layers with absorbed hydrogen was observed.

18

Plasma nitriding as a prevention method against hydrogen degradation of steel

Ćwiek J.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 36, nr 1

25-32

EN

Purpose: of this paper is evaluation of susceptibility to hydrogen degradation of structural low-alloy steel, plasma nitrided in the atmosphere with various contents of N2 and H2. Design/methodology/approach: Susceptibility of 34CrAlNi7-10 steel and samples with various plasma nitrided layers have been evaluated under monotonically increasing load in 0.005 M H2SO4 solution. The nitrided layers were investigated with the use of an X-ray Photoelectron Spectroscopy (XPS) and Auger Electrons Spectroscopy (AES). Slow-Strain Rate Tensile (SSRT) test was carried out under cathodic polarisation. Elongation, reduction in area, fracture energy and tensile strength were chosen as measures of susceptibility to hydrogen embrittlement. Fracture modes of failed samples were examined with the use of Scanning Electron Microscope (SEM). Findings: All tested samples revealed susceptibility to hydrogen degradation under hydrogenation. Samples with nitrided layer have lower lost of reduction in area than base metal samples. The nitrided layer established in standard atmosphere 30% H2 and 70% N2 has the highest resistance to hydrogen degradation. Research limitations/implications: Further research should be taken to reveal the exact mechanism of increased plasticity of nitrided layer with absorbed hydrogen. Practical implications: Plasma nitriding may prevent hydrogen charging of machines and vehicles parts in hydrogen generating environments, and thus decreasing susceptibility to hydrogen embrittlement. Originality/value: Under the increasing load and hydrogen generating environments plasma nitrided layers are effective barriers to hydrogen entry into a bulk of steel, and additionally increased plasticity of nitrided layers with absorbed hydrogen has been observed.

19

Hydrogen degradation of high-strength steels

Ćwiek J.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 37, nr 2

193-212

EN

Purpose: of this paper is to evaluate susceptibility of high-strength steels and welded joints to hydrogen degradation and to establish applicable mechanism of their hydrogen embrittlement and hydrogen delayed cracking. Design/methodology/approach: High-strength quenched and tempered steel grade S690Q and its welded joints have been used. Structural low-alloy steel 34CrAlNi7-10 with various plasma nitrided layers was evaluated. Susceptibility to hydrogen embrittlement of steel, welded joints, and nitrided layers was evaluated using monotonically increasing load. Slow strain rate test (SSRT) was carried out in hydrogen generating environments. Susceptibility to hydrogen delayed cracking was evaluated under constant load in artificial sea water. Fractographic examinations with the use of a scanning electron microscope (SEM) were performed to establish suitable mechanism of hydrogen-enhanced cracking. Findings: Tested high-strength steel and its welded joints are susceptible to hydrogen embrittlement when evaluated with the use of SSRT. The loss of plasticity is higher for welded joints then for the base metal. Tested steel and welded joints reveal high resistance to hydrogen degradation under constant load. Plasma nitrided layers are effective barriers for hydrogen entry into structural steel. Research limitations/implications: There has been no possibility to perform direct observations of exact mechanism of hydrogen-assisted cracking so far. Further research should be taken to reveal the exact mechanism of increased plasticity of a nitrided layer with absorbed hydrogen. Practical implications: Tested steel and its welded joints could be safely utilized within elastic range of stress in hydrogen generating environments, and constructions under cathodic protection provided that overprotection does not take place. Originality/value: Hydrogen-Enhanced Localized Plasticity (HELP) model is a more applicable mechanism of hydrogen degradation than the others for high-strength steels in hydrogen generating environments. Evidences of likely increased plasticity of nitrided layers with absorbed hydrogen were observed.

20

Plasma Nitriding as a Prevention Method Against Hydrogen Degradation of Steel

Ćwiek J.

Advances in Materials Science

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2009

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Vol. 9, nr 1(19)

4-13

EN

Aim of this paper is evaluation of susceptibility of plasma nitrided structural steel to hydrogen absorption and degradation. Structural steel, nitrided at glow discharge in the gas mixture of various N2, H2, Ar content was subjected to cathodic hydrogen charging in acid solution simulating the aged engine oil. The effect of the nitrided layers on the hydrogen transport and on the irreversible trapping was evaluated by the measurements of the hydrogen permeation rate and by the vacuum extraction, respectively. Surfaces with modified layers were examined with the use of a scanning electron microscope (SEM) before and after hydrogen permeation tests. In the presence of the not defected compact nitride layer, no hydrogen permeation through the steel has been stated under the experimental conditions. Absorbed hydrogen was accumulated within this layer. Using the atmosphere of the higher nitrogen to hydrogen ratio at plasma assisted nitriding provides the formation of thin compact nitride zone, highly protective against corrosion and hydrogen degradation.