Wyniki 1-10 spośród 10 dla zapytania: authorDesc:"Agnieszka Szczotok"

Revealing and evaluation of carbides in MAR M247 Ni based superalloy

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The work presents carbide phases occurring in a structure of MAR M247 Ni based superalloy. The ways of revealing these phases and results of using optical, scanning electron and transmission microscopy as well as X-ray phase analysis for researches are presented (Fig. 1÷10). The author’s attention has been concentrated on the carbides morphology and places of occurrence. INTRODUCTION [...]

Influence of methodical factors on results of a quantitative evaluation of gamma' phase in MAR M247 superalloy

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The nickel-based superalloy MAR M247 is precipitation strengthened by coherent with matrix gamma' precipitates. The superalloy was investigated by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The scanning electron microscopy images were used for a stereological evaluation of the gamma' precipitates size and shape, density and volume fra[...]

Influence of variable casting wall thickness and shell mold material and its thermal properties on secondary dendrite arm spacing in IN 713C superalloy castings DOI:10.15199/28.2016.5.2

  1. INTRODUCTION Different casting parameters can change the microstructure and mechanical properties of nickel-based superalloys. Kostić, Golubović, and Valčić [1] described how temperature gradient, crystal growth rate, and concentration of the alloying elements influence the microstructure and physical properties of the material. Polycrystalline and single-crystal nickel-based superalloy castings exhibit a dendritic structure that is the most common growth morphology during the solidification of metals and alloys. Each dendrite consists of primary arms (PDAs), secondary arms (SDAs), and even tertiary arms (TDAs). The secondary dendrite arm spacing (SDAS), which is defined as the distance between the protruding adjacent secondary arms of a dendrite (Fig. 1), has been recently used to describe the metallurgical structure of cast materials. It is well known that variations in the cooling rates during solidification can give rise to the various morphologies of the as-cast structures; these then lead to variations in their mechanical properties. Values of primary dendrite arm spacings (PDAS) and secondary dendrite arm spacings (SDAS) under controlled conditions can be used to predict the microstructure and properties of the castings and to develop a theoretical foundation for the control of microstructure and properties and the optimization of the industrial processing parameters. This has motivated many studies of PDAS and SDAS in dendritic structures [2÷6]. Along with the other microstructural parameters, PDAS and SDAS have a strong effect on the mechanical properties of Ni-based superalloys [5]. Over the past several decades, extensive experimental studies of PDAS have been carried out and a number of theoretical models have been developed [7÷11]. The relationships between the solidification processing parameters and PDAS have been established experimentally and theoretically [12]. Numerous studies of SDAS and dendrite growth [...]

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[...]

Application of a quantitative materialography methods for an evaluation of a structure repeatability of turbine blades made of MAR M247 nickel-based superalloy

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The results of studies on inhomogeneity of gas and shrinkage pores volume fraction, size and shape (Tab. 1) as well as size and shape of grains (Tab. 3) revealed during macroscopic analysis of experimental low pressure turbine blades of a jet engine made of MAR M247 nickel-based superalloy were characterized in the present work. The procedures of macro- and microstructure evaluation described[...]

Quantitative evaluation of γʹ phase in CMSX-4 superalloy

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The microstructure of nickel-base superalloys determines their mechanical behaviour. The strength of Ni-base superalloys is dependent on such factors as volume fraction, size, coarsening rate, and composition of γʹ phase precipitates [1]. The content and size of γʹ phase precipitates embedded in a cubic face-centred γ matrix can be adjusted by the alloy design and heat treatments. The composition of the ordered γʹ precipitates does differ, i.e. Ni3(Al, Ti, ...), and depends on the alloy composition and processing [2]. The characterization of γʹ phase precipitates in different nickelbased superalloys has been the subject of extensive research work. Volume fraction of the γʹ phase in Ni-base superalloys is a significant element influencing on working out the superalloys chemical compositions [3]. MATERIAL The measurements of γʹ phase precipitations were carried out on a monocrystalline cylindrical bar of 8 mm diameter made of CMSX-4 nickel-base superalloy [4]. The bar was cast in Laboratory of Material Research for Aircraft Industry in Rzeszów. The material was investigated in the as-cast condition. IMAGE ACQUISITION AND ANALYSIS OF γʹ PHASE PRECIPITATES The bar intended for investigations was cut perpendicularly to the main axis. The procedure of metallographic specimen preparation was described in details in Table 1. Quantitative metallography of CMSX-4 requires the revealing of γʹ precipitates by means of an appropriate etching conditions selection as well as use of appropriate image acquisition in order to observe the γʹ precipitates and register the images of the superalloy microstructure with them. In the previous work two etching methods of the γʹ phase precipitates were described [5]. For a quantitative evaluation of the precipitates etchant caused their etching and leaving the γ matrix is better, so in the ca[...]

Grain imaging and measurement on cross-section of turbine blade using EBSD and optical methods

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Turbine blades are termed Flight Safety Parts (FSP). Imaging and measurement of grain in case of the blades is very important, because grain size, shape and distribution strongly affect the mechanical properties of the blades. The size and shape of primary grain are basic structural criteria for quality evaluation of precision cast products from nickel-based superalloys. The evaluation of fine-grained product is of great importance to metallurgists. This work which has traditionally been carried out using light microscopy can be performed by means of the electron backscattered diffraction (EBSD) technique used in the scanning electron microscope (SEM). EBSD is nowadays capable of undertaking such a study. EBSD has been known for many years (the diffraction of electrons was first observed in 1928 by Kikuchi [1]), but only widely applied in the last 10 years. EBSD is now a fast, automated technique which is utilized to determine microtexture (texture on the scale of the microstructure), microstructure quantification, grain and phase boundary characterization, phase identification and strain determination [2÷4]. EBSD is based on acquisition and analysis of Kikuchi diffraction patterns from the subsurface of a specimen in an SEM. In EBSD a stationary electron beam strikes a tilted crystalline sample and the diffracted electrons form a pattern on a fluorescent screen. The diffraction pattern can be used to measure the crystal orientation, as well as boundary misorientations, discriminate between different materials, and provide information about local crystalline perfection. When the beam is scanned in a grid across a polycrystalline sample and the crystal orientation is measured at each point, the resulting map reveals the constituent grain morphology, orientations and boundaries. Electron backscatter diffraction technique to measure grain-specific orientations and misorientations was first recorded more than 20 years ago [5] and[...]

Laser treatment of heterogeneous surfaces formed by electro-spark deposition DOI:10.15199/28.2017.6.5

  1. INTRODUCTION The life of many machine parts can be significantly extended by enhancing the tribological properties of the surfaces. Better durability of surfaces can be achieved by coatings of appropriate materials. Coatings with various desired properties have been already developed and are already widely used with great economical benefits. The technologies, that have been developed for this purpose, are referred to as Surface Engineering. There is an ever increasing requirement for low cost coatings with high quality tribological properties of its surfaces for wider applications with combined requirements. Examples are machine elements subjected to sever conditions, such as friction and wear, corrosion, or exposure to high temperature. For example, coatings of shafts of rotating machinery have combined requirements. There is a need to increase the hardness of the surfaces rotating inside the bearings to resist wear, and increase the load capacity of the surface, while the core of the shaft must retain its original plasticity, in order to prevent failure due to brittle cracking under the impact forces in operating machinery. In addition, the coating must have good bonding to the substrate material of the machine element in order to avoid undesired peeling (delamination). It has been already realized that heterogeneous surfaces, are advantageous for such combined requirements. They are designed to have the desired distribution of composition and gradients of various properties, such as microhardness, along the thin width of the coating. There are many methods for surface coatings such as electroplating or plasma spraying [1÷6]. Very thin layers can be deposited by vapour deposition. Various surface treatment techniques have been developed to improve the desired properties of the deposited layers, based on the substrate material. One important low cost method is the electro-spark deposition (ESD), which has been recognized [...]

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