Wyniki 1-4 spośród 4 dla zapytania: authorDesc:"Barbara Kościelniak"

Characterization of IN713C superalloy microstructure after high temperature creep test by LM, SEM and STEM DOI:10.15199/28.2016.2.1

  This work focuses on the influence of creep phenomenon on the cast IN713C nickel-based superalloy. The carrot-shape IN713C superalloy castings were produced in an investment casting cluster mould and the creep test samples were then prepared from the castings. The creep tests were carried out in order to investigate processing-microstructure-property relationships. The resultant macro- and microstructures were observed and characterized after the creep tests using light microscopy, scanning electron microscopy and scanning transmission electron microscopy. The aim of the analysis was to reveal the changes in the microstructure that occurred as a result of the creep and to identify the phases that participate in voids formation, and crack generation and propagation during the creep tests. It was confirmed that the creep resistance of the IN713C superalloy is negatively affected by some structural characteristics such as porosity, (γ + γ′) eutectic or carbide precipitates along the grain boundaries. Our work confirms that a combination of thermal conditions with a tensile force affected the microstructure of IN713C nickel-based superalloy causing changes in morphologies of the existing precipitations and phase transformations, as in the case of the carbides. Additionally, carbide sulphides containing primarily Zr and intermetallic phase including mainly Ni and Zr were observed. Key words: IN713C, superalloy, creep, microstructure.1. INTRODUCTION Creep, fatigue and the interaction between them play important roles in determining the lifetime of many device components used at elevated temperature. Turbine blades made of nickel-based superalloys are subjected to complex thermal and mechanical creep and fatigue loads [1, 2], resulting in a marked change in microstructure during creep as the originally cubic morphology of the γ′ precipitates becomes directionally coarsened (raft-like) perpendicular to the direction of t[...]

Charakterystyka mikrostruktury nadstopu IN713C po próbie pełzania w wysokiej temperaturze za pomocą metod LM, SEM i STEM DOI:

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1. CEL PRACY Artykuł dotyczy wpływu zjawiska pełzania na strukturę odlewniczego nadstopu na osnowie niklu IN713C. Makro- i mikrostrukturę materiału uzyskaną w efekcie przeprowadzonej próby pełzania obserwowano przy różnych powiększeniach. Celem badań było ujawnienie zmian struktury, jakie pojawiły się w efekcie pełzania i zidentyfikowanie faz, które brały udział w powstawaniu nieciągłości materiału oraz generowaniu i propagacji pęknięć podczas próby pełzania. 2. MATERIAŁ I METODYKA BADAŃ Materiałem przeznaczonym do badań był nadstop IN713C na osnowie niklu. Dzięki niskiej cenie, dobrej lejności, stabilności mikrostruktury i właściwościom mechanicznym w wysokiej temperaturze IN713C jest stosowany do odlewania łopatek turbin niskiego ciśnienia. Na ry[...]

Characteristic of cyclic oxidation of chosen austenitic steels in a steam atmosphere DOI:10.15199/40.2016.1.1

  The aim of the study was to evaluate the oxidation resistance of chromium-nickel austenitic steels in an atmosphere, which contains oxygen and steam at a temperature of 750oC. The oxidation test of steel samples X2CrNiMo17-12-2, X6CrNiMoTi17- 12-2, Super 304H and HR3C was carried out in a cyclic mode, made up of 100 cycles trials of 2 hours. The results show the mass changes of steels caused by a cyclic oxidation. The morphology and chemical composition of the oxide layer formed on the surface of tested samples were also described. It has been proved that under these conditions HR3C steel shows the best heat resistance and X2CrNiMo17-12-2 steel presents the worst tendency of oxides to defoliation. Keywords: austenitic steels, cyclic oxidation, steam Charakterystyka cyklicznego utleniania w parze wodnej wybranych stali austenitycznych Celem badań była ocena odporności na utlenianie austenitycznych stali chromowo-niklowych w atmosferze zawierającej tlen i parę wodną w temperaturze 750oC. Utlenianie próbek ze stali X2CrNiMo17-12-2, X6CrNiMoTi17-12-2, Super 304H i HR3C przeprowadzono w sposób cykliczny, składający się ze 100 cykli trwających 2 godziny. Przedstawiono wyniki zmiany masy materiałów wywołanych cyklicznym utlenianiem. Scharakteryzowano również morfologię i skład chemiczny warstw tlenkowych powstałych na powierzchni badanych stali. Wykazano, że najlepszą żaroodporność w tych warunkach posiada stal HR3C, a najgorszą stal X2CrNiMo17-12-2 wykazująca skłonność do defoliacji tlenków. Słowa kluczowe: stale austenityczne, utlenianie cykliczne, para wodna 1. Introduction Domestic energy sector is outdated and contains many power plants, which are characterized by low efficiency of power units, large increase of their failure and being below the standards of NOx, SO2 and CO2 emission [2]. Development of national energy is heading towards increasing the productivity, efficiency and significant reduction of emissions of harmful substances[...]

Material and technological issues in production of electrostatic precipitators collecting electrodes DOI:10.15199/28.2017.4.7

  1. INTRODUCTION Collecting electrodes along with emitting ones are the most important components of electrostatic precipitators. On Polish market and abroad there are available a few topologies of collecting electrodes (Fig. 1) [1]. Combustion and industrial gases are loaded with mineral matter like ash. Collecting electrodes are designed in order to collect this matter deposited by electrostatic charge. Afterward this deposit are removed by forced vibration caused by hitting the assembly beam with a hammer (Fig. 2) [2]. A collecting electrode should effectively collect ash during changing conditions of ESP (ESP — electrostatic precipitators) operation. Leading producers of ash removing devices use formed profiles of Sigma type. This topology of electrodes combines the following basic features: high elasticity and rigidity resulting in efficient ash removal, fast dynamic reaction to hitting; limited release, erosion of the ash into the gas because of profile of the electrodes [3, 4]. Sigma type electrodes hang on the upper beam where their twist is limited. The bottom assembly of electrodes is rigid due to screws and a beam. Such structure allows accelerations in the range of 100÷140 g during ash removal by forced vibration. According to [5] efficient ash removal from collecting electrodes requires around 100 g acceleration. Efficiency of ash collection with collecting electrodes and how ease they can be cleaned depends on their topology and material used for manufacturing. The more elastic this material is and faster vibrations are transferred, the higher efficiency can be expected [1]. Taking into account this relation producers state their demands concerning mechanical features of steel strips for production of collecting electrodes by roll forming. It is often observed that cheap steel grades are used because the market situation leads to growing competition between ESP producers, and price is the decisive criterion. To date progress in techno[...]

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