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1
Content available High Temperature Oxidation Property of Ni Based Superalloy CM247LC Produced Via Selective Laser Melting Process
Lee Jung-Uk, Kim Young-Kyun, Seo Seong-Moon, Lee Kee-Ahn
Archives of Metallurgy and Materials
|
2023
|
Vol. 68, iss. 1
107--112
EN
CM247LC alloy was manufactured by using selective laser melting (SLM) process, one of the laser powder bed fusion (L-PBF) methods. The hot isostatic pressing (HIP) process was additionally conducted on the SLM-built CM247LC to control its microstructures and defects. The high temperature oxidation property was investigated, and it was compared with conventional DS247LC sample (reference) prepared via the directional solidification process. The L-PBF HIP sample showed blocky-type MC carbides generated along the grain boundary with average size of about 200 nm. A semi-spherical primary γ' phase of size 0.4-1.0 μm was also observed inside the grains. Moreover, the DS247LC sample displayed a coarse eutectic γ' phase and many script-type MC carbides. Furthermore, cuboidal-type γ' with an average size of about 0.5 μm was detected. High-temperature oxidation tests were conducted at 1000°C and 1100°C for 24 hours. The results at 1100°C oxidation temperature showed that the measured oxidation weight gains for HIP and DS247LC were 1.96 mg/cm2 and 2.26 mg/cm2, respectively, indicating the superior high-temperature oxidation resistance of the L-PBF HIP sample. Based on the above results, a high-temperature oxidation mechanism of the CM247LC alloys manufactured by the SLM process and the directional solidification process has been proposed.
2
Content available Effect of Growth Rate on Coarsening of Secondary Dendrite Arm Spacings in Directionally Solidified of Al-8.8La-1.2Ni Ternary Alloy
Üstün Erkan, Çadirli Emin
Archives of Metallurgy and Materials
|
2022
|
Vol. 67, iss. 3
931--938
EN
One of the most important factors directly affecting microstructure and mechanical properties in directional solidification process is secondary dendrite arm spacing (SDAS). It is very important to measure the SDAS and examine the factors that may affect them. To investigate the effect of growth rate on the SDAS, the alloy specimens were directional solidified upward with different growth rates (V = 8.3-83.0 μm/s) at a constant temperature gradient (G = 4 K/mm) in a Bridgman-type growth apparatus. After the specimens are directionally solidified, they were exposed to metallographic processes in order to observe the dendritic solidification structure on the longitudinal section of the specimens. Coarsen secondary dendrite arm spacings (λ2C) were measured excluding the first arms near the tip of the dendrite. Local solidification times ( tf) were calculated by ratio of spacings to growth rates. It was determined that the tf values decreased with increasing V values. The relationships between tf and λ2C were defined by means of the binary regression analysis. Exponent values of tf were obtained as 0.37, 0.43, 0.46 and 0.47 according to increasing V values, respectively. These exponent values are close to the exponent value (0.33) predicted by the Rappaz-Boettinger theoretical model and good agreement with the exponent values (0.33-0.50) obtained by other experimental studies.
3
Content available Characteristics of the Growth of the Directionally Solidified Fe-4.25% C Eutectic Alloy
Trepczyńska-Łent Małgorzata
Archives of Metallurgy and Materials
|
2021
|
Vol. 66, iss. 4
1179--1186
EN
The current work is dedicated to the mathematical description of a protrusion of the leading phase (cementite) over the wetting phase (austenite) observed during the author’s experiments in previous articles. A cementite protrusion is confirmed in the directionally solidified Fe-4.25% C eutectic alloy. The protrusion is defined due to the mass balance fulfilment. A coordinate system is attached to the solid/liquid interface, which is moving with the constant growth rate v.
4
Content available Modelling the composition of carbides in nickel-based superalloys of directional crystallization
Glotka O. A.
Journal of Achievements in Materials and Manufacturing Engineering
|
2020
|
Vol. 102, nr 1
5--15
EN
Purpose: The specifics of the influence of alloying elements on the chemical composition of various types of carbides, their topology and morphology for a multicomponent system of the type Ni-5Cr-9Co-6Al-1Ti-11.7W-1.1Mo-1.6Nb-0.15C using the calculation method CALPHAD. It is shown that the obtained dependences closely correlate with thermodynamic processes occurring in the system. Design/methodology/approach: This work presents the results of studies of the distribution of chemical elements in the composition of carbides, depending on their content in the system. Findings: It was found that the influence of alloying elements on the composition of carbides is complex and is described by complex. Research limitations/implications: An essential problem is the prediction of the structure and properties of heat-resistant alloys without or with a minimum number of experiments. Practical implications: The obtained dependences can be used both for designing new heat-resistant alloys and for improving the compositions of industrial alloys. Originality/value: The value of this work is that the obtained dependences of the influence of alloying elements on the dissolution (precipitation) temperatures and the distribution of elements in carbides in the alloy of the Ni-5Cr-9Co-6Al-1Ti-11.7W-1.1Mo-1.6Nb-0.15C.
5
Content available Leading Phase in the Directionally Solidifying Fe – 4.25%C Eutectic Alloy
Trepczyńska-Łent M.
Archives of Foundry Engineering
|
2019
|
iss. 4
113--116
EN
In order to determine the leading phase of the Fe - 4.25% C eutectic alloy, the method of directional crystallization, which allows to study the character of the solid / liquid growth front, was used. Examined eutectic was directionally solidified with a constant temperature gradient of G = 33,5 K/mm and growth rate of v = 125 μm/s (450 mm/h). The Bridgman technique was used for the solidification process. The sample was grown by pulling it downwards up to 30 mm in length. The alloy quenched by rapid pulling down into the Ga-In-Sn liquid metal. The sample was examined on the longitudinal section using a light microscope and scanning electron microscope. The shape of the solid/liquid interface and particularly the leading phase protrusion were revealed. The formation of the concave – convex interface has been identified in the quasi-regular eutectic growth arrested by quenching. The cementite phase was determined to be a leading phase. The total protrusion d is marked in the adequate figure.
6
Content available Preparation of Twinned Dendrites of Al-Zn Alloy with High Zn Content
Gao K., Song W., Fan L., Ding Y., Guo X., Zhang R.
Archives of Metallurgy and Materials
|
2018
|
Vol. 63, iss. 4
1657--1662
EN
Twinned dendrites in Al-Zn alloy with high Zn content (40% wt.%) were successfully prepared by directional solidification. At different directional solidification rates (1000 and 1500 μm/s), microstructures and growth orientation variations of Al twinned dendrite and non-twinned dendrite were characterized. By using the inverted trapezoidal graphite sleeve at 1000 μm/s, Al twinned dendrite were formed to developed feather crystal structures in longitudinal section. Its primary and secondary twinned dendrite were grew along [110] direction. Moreover the deviation angle between [110] direction of Al twinned dendrite and the heat flow direction was about 27.15°. While not using the inverted trapezoidal graphite sleeve at 1000 and 1500 μm/s, Al dendrite was the non-twinned dendrite and the twinned dendrite was not appeared. The experimental results showed that the higher temperature gradient, a certain pulling rate and convection environment were the formation conditions of twinned dendrites.
7
Content available Study of Microstructure of Oriented Eutectic Fe-C Alloy
Trepczyńska-Łent M.
Archives of Foundry Engineering
|
2018
|
Vol. 18, iss. 1
123--128
EN
Fe - 4,25% C alloy was directionally solidified with a constant temperature gradient of G = 33,5 K/mm and growth rate of v = 83,3 μm/s (300 mm/h) using a vacuum Bridgman-type crystal growing facility with liquid metal cooling technique. To reveal more detailed microstructure, the deep etching was made. This was obtained in the process of electrolytic dissolution. The microstructure of the sample was examined on the longitudinal and transverse sections using an Optical Microscope and Scanning Electron Microscope. Using the Electron Backscattered Diffraction technique, phase map and analysis of phase were made. In this paper the analysis of Fe-C alloy eutectic microstructure is presented. Regular eutectic structure was obtained. The fracture surfaces show lamellar structure. Microscopic observation after electrolytic extraction indicates that the grains of longitudinal shape of eutectic cementite have been obtained. These grains are characterized by layered construction with many rounded discontinuities.
8
Content available Solid-liquid interface morphology of white carbide eutectic during directional solidification
Trepczyńska-Łent M.
Archives of Metallurgy and Materials
|
2017
|
Vol. 62, iss. 1
365--368
EN
In this paper the analysis of solid-liquid interface morphology in white carbide eutectic was made. In a vacuum Bridgman-type furnace, under an argon atmosphere, directionally solidified sample of Fe - C alloy was produced. The pulling rate was v = 125 μm/s (450 mm/h) and constant temperature gradient G = 33.5 K/mm. The microstructure of the sample was frozen. The microstructure of the sample was examined on the longitudinal section using an light microscope and scanning electron microscope.
9
Content available Assessment of Mechanism of Pore Formation in Directionally Solidified A356 Alloy
Uludag M., Dispinar D.
Archives of Foundry Engineering
|
2017
|
Vol. 17, iss. 1
157--162
EN
It is well-known that the better the control of the liquid aluminium allows obtaining of better properties. One of the most important defects that is held responsible for lower properties has been the presence of porosity. Porosity has always been associated with the amount of dissolved hydrogen in the liquid. However, it was shown that hydrogen was not the major source but only a contributor the porosity. The most important defect that causes porosity is the presence of bifilms. These defects are surface entrained mainly due to turbulence and uncontrolled melt transfer. In this work, a cylindrical mould was designed (Ø30 x 300 mm) both from sand and die. Moulds were produced both from sand and die. Water cooled copper chill was placed at the bottom of the mould in order to generate a directional solidification. After the melt was prepared, prior to casting of the DC cast samples, reduced pressure test sample was taken to measure the melt quality (i.e. bifilm index). The cast parts were then sectioned into regions and longitudinal and transverse areas were investigated metallographically. Pore size, shape and distribution was measured by image analysis. The formation of porosity was evaluated by means of bifilm content, size and distribution in A356 alloy.
10
Content available XRD and EBSD Measurements of Directional Solidification Fe-C Eutectic Alloy
Trepczyńska-Łent M.
Archives of Foundry Engineering
|
2016
|
Vol. 16, iss. 4
169--174
EN
In a vacuum Bridgman-type furnace, under an argon atmosphere, directionally solidified sample of Fe-C alloy was produced. The pulling rate was v = 83 μm/s (300 mm/h) and constant temperature gradient G = 33,5 K/mm. The microstructure of the sample was examined on the longitudinal section using an Optical Microscope and Scanning Electron Microscope. The X-ray diffraction and electron backscatter diffraction technique (EBSD) have been used for the crystallographic analysis of carbide particles in carbide eutectic. The X-ray diffraction was made parallel and perpendicular to the axis of the goniometer. The EBSD shows the existence of iron carbide Fe3C with orthorhombic and hexagonal structure. Rapid solidification may cause a deformation of the lattice plane which is indicated by different values of the lattice parameters. Such deformation could also be the result of directional solidification. Not all of the peaks in X–ray diffractograms were identified. They may come from other iron carbides. These unrecognized peaks may also be a result of the residual impurity of alloy.
11
Content available Solidification Front of Oriented Ledeburite
Trepczyńska-Łent M., Olejnik E.
Archives of Foundry Engineering
|
2016
|
Vol. 16, iss. 1
124--130
EN
Directional solidification of the Fe - 4,3 wt % C alloy was performed with the pulling rate equal to v=83 μm/s. Sample was frozen during solidification to reveal the shape of the solid/liquid interface. Structures eutectic pyramid and spherolitic eutectic were observed. The solidification front of ledeburite eutectic was revealed. The leading phase was identified and defined.
12
Content available X-ray Diffraction Study of Directional Solidification Ledeburite
Trepczyńska-Łent M., Szykowny T.
Archives of Foundry Engineering
|
2015
|
Vol. 15, iss. 3
71--76
EN
Directionally solidified sample of Fe-Fe3C eutectic alloy were produced under an argon atmosphere in a vacuum Bridgman-type furnace to study the eutectic growth with v = 167 μm/s pulling rate and constant temperature gradient G = 33.5 K/mm. Since how the growth texture of eutectic cementite is related to its growth morphology remains unclear, the current study aims to examine this relationship. The technique such as X-ray diffraction, have been used for the crystallographic analysis of carbide particles in white cast irons.
13
Content available Thermodynamic Assessment of Mushy Zone in Directional Solidification
Mikołajczak P., Ratke L.
Archives of Foundry Engineering
|
2015
|
Vol. 15, iss. 4
101--109
EN
Solidification of AlSiFe alloys was studied using a directional solidification facility and the CALPHAD technique was applied to calculate phase diagrams and to predict occurring phases. The specimens solidified by electromagnetic stirring showed segregation across, and the measured chemical compositions were transferred into phase diagrams. The ternary phase diagrams presented different solidification paths caused by segregation in each selected specimen. The property diagrams showed modification in the sequence and precipitation temperature of the phases. It is proposed in the study to use thermodynamic calculations with Thermo-Calc which enables us to visualize the mushy zone in directional solidification. 2D maps based on property diagrams show a mushy zone with a liquid channel in the AlSi7Fe1.0 specimen center, where significant mass fraction (33%) of β-Al5FeSi phases may precipitate before α-Al dendrites form. Otherwise liquid channel occurred almost empty of β in AlSi7Fe0.5 specimen and completely without β in AlSi9Fe0.2. The property diagrams revealed also possible formation of α–Al8Fe2Si phases.
14
Content available Anisotropic in Situ Metal Matrix Composite Reinforced with VC Carbide Fibres
Kawalec M., Górny M., Sikora G.
Archives of Foundry Engineering
|
2015
|
Vol. 15, iss. 1
21--24
EN
A eutectic reaction is a basic liquid-solid transformation, which can be used in the fabrication of high-strength in situ composites. In this study an attempt was made to ensure directional solidification of Fe-C-V alloy with hypereutectic microstructure. In this alloy, the crystallisation of regular fibrous eutectic and primary carbides with the shape of non-faceted dendrites takes place. According to the data given in technical literature, this type of eutectic is suitable for the fabrication of in-situ composites, owing to the fact that a flat solidification front is formed accompanied by the presence of two phases, where one of the phases can crystallise in the form of elongated fibres. In the present study an attempt was also made to produce directionally solidifying vanadium eutectic using an apparatus with a very high temperature gradient amounting to 380 W/cm at a rate of 3 mm/h. Alloy microstructure was examined in both the initial state and after directional solidification. It was demonstrated that the resulting microstructure is of a non-homogeneous character, and the process of directional solidification leads to an oriented arrangement of both the eutectic fibres and primary carbides.
15
Content available Effect of Contact Gap in Directional Solidification of AlSiFe Alloys
Mikołajczak P., Ratke L.
Archives of Foundry Engineering
|
2014
|
Vol. 14, iss. 3 spec.
41--44
EN
One of the methods to study solidification of alloys and metals is directional solidification. In the paper the effect of the contact gap between the analyzed specimen and the bottom heater was analysed. The occurring contact gap caused the increase in planned solidification velocity. For the facility calibration the methodology with M coefficient was applied. The experiments revealed efficient values of M and allowed to conduct efficiently the directional solidification of AlSiFe alloys in wide range of growth rates. The effect of the contact gap seems to be random phenomena and most difficult factor influencing precisely planned directional solidification.
16
Content available Directional Solidification of AlSi Alloys with Fe Intermetallic Phases
Mikołajczak P., Ratke L.
Archives of Foundry Engineering
|
2014
|
Vol. 14, iss. 1
75--78
EN
Directional solidification technique is an important research instrument to study solidification of metals and alloys. In the paper the model [6,7,8] of directional solidification in special Artemis-3 facility was presented. The current work aimed to propose the ease and efficient way in calibrating the facility. The introduced M coefficient allowed effective calibration and implementation of defined thermal conditions. The specimens of AlSi alloys with Fe-rich intermetallics and especially deleterious β-Al5FeSi were processed by controlled solidification velocity, temperature gradient and cooling rate.
17
Application of EBSD technique to investigation of modern materials for aero engines turbine blades
Chmiela B., Sozańska M., Cwajna J.
Inżynieria Materiałowa
|
2013
|
Vol. 34, nr 3
140--144
EN
Aero engine turbine blades are fiight safety critical components and are first and foremost characterized by superior mechanical properties. The mechanical properties can be improved by replacing equiaxed (EQ) polycrystalline blades by directionalÍy solidified (DS) and single crystal blades (SX). During directional solidification, many defects may form, e.g. freckles and stray grains. By comoining the techniques of scanning electron microscopy (SEM), energy-dispersive x-ray microanalysis (EDS), and electron backscatter diffraction (EBSD), these defects can be comprehensively evaluated. Freckles are casting defects appearing on the surface of DS and SX castings and take the form of long chains of equiaxed grains aligned parallel to gravity. Freckles form mainly because of thermosolutal convection and buoyancy forces in the mushy zone, which in turn are caused by density inversion in the interdendritic liquid. Other casting defects are stray grains as a result of poor efficiency of the helical grain selector. Obtained results reveal some new details about freckle formation and stray grains formation mechanisms.
PL
Łopatki turbin silników lotniczych są elementami krytycznymi o bezpośrednim wpływie na bezpieczeństwo lotu, dlatego muszą charakteryzować się bardzo dobrymi właściwościami mechanicznymi. Właściwości mechaniczne mogą zostać ulepszone dzięki zastępowaniu łopatek polikrystalicznych o ziarnach równoosiowych (EQ) łopatkami kierunkowo krystalizowanymi (DS) i monokrystalicznymi (SX). Podczas kierunkowej krystalizacji mogą pojawić się wady odlewów, takie jak frekle (freckles) czy obce ziarna (stray grains). Połączenie technik elektronowej mikroskopii skaningowej (SEM), mikroanalizy rentgenowskiej z dyspersją energii (EDS) oraz dyfrakcji elektronów wstecznie rozproszonych (EBSD) umożliwia kompleksowy opis tych wad. Frekle to powierzchniowe wady odlewów DS i SX mające postać łańcuchów równoosiowych ziaren ułożonych równolegle do kierunku działania grawitacji. Frekle są skutkiem działania sił wyporu hydrostatycznego i konwekcji w strefie ciekło-stałej, które wynikają z inwersji gęstości ciekłego stopu w obszarach międzydendrytycznych. Innym przykładem wad są obce ziarna, będące skutkiem małej sprawności śrubowego selektora ziarna. Otrzymane wyniki ujawniają pewne nowe szczegóły dotyczące powstawania frekli i obcych ziaren.
18
Content available Possibilities of the materials properties improvement for the cementite eutectic by means of unidirectional solidification
Trepczyńska-Łent M.
Archives of Metallurgy and Materials
|
2013
|
Vol. 58, iss. 3
987--991
EN
The paper brings the results of directional solidification of Fe-Fe3C eutectic alloy. The Bridgman method with vertical thermal gradient in conducted research was applied. Two values of rate was used for sample movement testing. One sample after solidification, was immediately taken of the cooler. The distribution of thermal gradient in the alloy was determined. The value of thermal gradient in liquid at the solidification front was determined. On the samples, where cementite eutectic was oriented, interphase spacing λ was measured. The results of the dependence between parameters v and λ were presented. The research with application of optical microscope and computer programme to image analysis NIS-Elements was used.
PL
W pracy przedstawiono rezultaty kierunkowej krystalizacji stopu eutektycznego Fe-Fe3C. Wykorzystano metodę Bridgmana z pionowym gradientem temperatury. Zastosowano dwie prędkości przemieszczania próbki. Jedna z próbek, po zrealizowaniu krystalizacji została zamrożona. Określono rozkład gradientu temperatury w stopie oraz wyznaczono wartość gradientu temperatury w cieczy na froncie krystalizacji. Na próbkach przeprowadzono pomiary odległości międzyfazowej λ. Przedstawiono wyniki badań określających zależności pomiędzy parametrami v i λ. W badaniach wykorzystano mikroskop optyczny oraz program do komputerowej analizy obrazu NIS-Elements.
19
Content available Directional solidification of ledeburite
Trepczyńska-Łent M.
Archives of Foundry Engineering
|
2013
|
Vol. 13, iss. 3
101--106
EN
Directional solidification of ledeburite was realised out using a Bridgman’s device. The growth rate for movement sample v=83.3 μm/s was used. In one sample the solidification front was freezing. The value of temperature gradient in liquid at the solidification front was determined. Interfacial distance λ on the samples was measured with NIS-Elements application for image analysis.
20
Content available Identification and evaluation of freckles in directionally solidified casting made of PWA 1426 nickel-based superalloy
Chmiela B., Sozańska M., Cwajna J.
Archives of Metallurgy and Materials
|
2012
|
Vol. 57, iss. 2
559-564
EN
Manufacturing of modern aero engine turbine blades made of nickel-based superalloys is very complex and expensive. The thrust and performance of new engines must address constantly more demanding requirements. Therefore, turbine blades must be characterised by very good mechanical properties, which is possible only if the blades are free of casting defects. An important innovation has been the launching of directionally solidified (DS) and single crystal (SX) turbine blades. But, manufacturing procedures and the chemical composition of many superalloys promote the formation of casting defects that are characteristic only for directional solidification. One of these defects is freckles. Freckles are small equiaxed grains in the form of long chains parallel to the solidification direction and are located on the surface of the casting. Freckles decrease the mechanical properties of DS and SX blades; therefore, they should be always unambiguously identified to improve the manufacturing process. This work presents the possibilities of identifying and evaluating freckles in DS casting made of PWA 1426 superalloy by combining the scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and electron backscatter diffraction (EBSD) techniques.
PL
Wytwarzanie łopatek turbin nowoczesnych silników lotniczych jest bardzo złożone i kosztowne. Stale rosną też wymagania dotyczące ciągu i sprawności nowych silników. Dlatego łopatki turbin musza charakteryzować się bardzo dobrymi właściwościami mechanicznymi. Jest to możliwe tylko wtedy, gdy łopatki nie wykazują wad odlewniczych. Ważną innowacją w wytwarzaniu łopatek było wprowadzenie łopatek kierunkowo krystalizowanych (DS) i monokrystalicznych (SX). Skład chemiczny wielu nadstopów i proces wytwarzania łopatek stanowią czasem czynniki sprzyjające powstawaniu wad odlewniczych, charakterystycznych tylko dla procesu kierunkowej krystalizacji. Przykładem takiej wady są frekle. Wada ta ma postać małych, równoosiowych ziaren tworzących łańcuchy, przeważnie równoległe do kierunku krystalizacji. Wada ta znacznie obniża właściwości mechaniczne łopatek DS i SX, dlatego powinna być zawsze jednoznacznie identyfikowana w celu usprawnienia procesu ich wytwarzania. W pracy przedstawiono możliwości identyfikacji i oceny wady frekle w kierunkowo krystalizowanym odlewie z nadstopu niklu PWA 1426 przy użyciu elektronowej mikroskopii skaningowej (SEM), mikroanalizy rentgenowskiej (EPMA) i dyfrakcji elektronów wstecznie rozproszonych (EBSD).
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