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Szeliga D.,Rzeszow University of Technology | Szeliga D.,Research and Development Laboratory for Aerospace Materials | Kubiak K.,Rzeszow University of Technology | Kubiak K.,Research and Development Laboratory for Aerospace Materials | And 3 more authors.
International Journal of Cast Metals Research | Year: 2014

On the basis of numerical simulation and conducted microstructure analysis, it was established that the application of SiC chills results in significant decrease in shrinkage porosity, in comparison to castings without chills. The temperature measurement was carried out, and the influence of chills on the kinetics of solidification process was established. It was determined that the application of SiC chills causes the increase in cooling rate (y0.1 K s21), in comparison to the casting without chills. The authors carried out numerical optimisation with the use of ProCAST software and established which parameters have the largest influence on the solidification process of castings with and without chills. In addition to SiC, the graphite and Al2O3 were analysed as chill material in terms of influence on the predicted kinetics of cooling process and the shrinkage porosity of castings. The conditions of solidification process for castings, which are equipped with chills and are free from shrinkage porosity, were determined on the basis of obtained results. © 2014 W. S. Maney & Son Ltd. Source


Szeliga D.,Rzeszow University of Technology | Szeliga D.,Research and Development Laboratory for Aerospace Materials | Kubiak K.,Rzeszow University of Technology | Kubiak K.,Research and Development Laboratory for Aerospace Materials | And 2 more authors.
Journal of Materials Processing Technology | Year: 2016

The influence of internal thermal baffle between casting and central rod of the ceramic mould on the shape of liquidus isotherm was studied. Convex or nearly flat shape of solidification front was obtained after selection of suitable location of internal thermal baffle relative to the platform, based on measured and predicted temperature distribution. The results were compared with those acquired for castings manufactured with the use of standard mould. Application of internal thermal baffle brought about decrease of solidification front curvature, as well as transverse temperature gradient Gx = 0.2 °C/mm and maximum undercooling value ΔTm = 16.5°C, which succeeded in proper growth of dendrites compared with Gx = 2.8 °C/mm and ΔTm = 36.5 °C in the mould without internal baffle. The convex shape of liquidus isotherm induced directional course of solidification process in the area, where casting cross-section changed significantly its dimensions, but it also led to excessive growth of shrinkage porosity on the platform surface. The increase of the distance between the platform and thermal baffle resulted in significant reduction of amount and size of pores along the length of the internal zone of platform. © 2016 Elsevier B.V. All rights reserved. Source


Szeliga D.,Rzeszow University of Technology | Szeliga D.,Research and Development Laboratory for Aerospace Materials | Kubiak K.,Rzeszow University of Technology | Kubiak K.,Research and Development Laboratory for Aerospace Materials | And 5 more authors.
Journal of Materials Engineering and Performance | Year: 2014

The paper presents the analysis of numerical simulation of the Bridgman directional solidification process performed on CMSX-4 rods. The numerical simulation was studied applying the ProCAST software. The constitutive law parameters of the normal Gaussian distribution were used to describe the nucleation process. The coefficients of the equation were determined and used to calculate the growth rate of dendrite tip. The analysis of the as-cast microstructure was carried out with the use of Aphelion software in order to determine the average area of grains and their quantity. The experimental verification of both nucleation and grain growth coefficients used for the simulation of the directional solidification process confirmed that the model was correct and described well the investigated process of directional solidification using the Bridgman method. © 2013 The Author(s). Source


Szeliga D.,Rzeszow University of Technology | Szeliga D.,Research and Development Laboratory for Aerospace Materials | Kubiak K.,Rzeszow University of Technology | Kubiak K.,Research and Development Laboratory for Aerospace Materials | And 4 more authors.
Vacuum | Year: 2016

The method of temperature measurement in directionally solidified (DS) Ni-based CMSX-4 superalloy castings manufactured using withdrawal rates of 3 and 5 mm/min in the Bridgman furnace with graphite heaters, was successfully improved. The numerical simulation of directional solidification process was performed with the use of ProCAST software, for withdrawal rates of 1, 3 and 5 mm/min in order to predict cooling rate, axial and transverse temperature gradients, solidification rate, height of mushy zone, shape of liquidus isotherm and its location relative to thermal baffle along the casting height. The critical distance from chill plate, above which of the steady-state solidification process starts, was established. The liquidus isotherm attained the concave, convex or flat shape, in dependence on withdrawal rate of casting and the distance from chill plate. The relationship between the shape of liquidus isotherm and grain structure was found for castings withdrawn at 1 and 5 mm/min. Grains grew in the direction of the rod axis and that of casting surface for the concave and convex isotherm shape, respectively. The flat shape of liquidus isotherm induced grain growth in the direction which was the most parallel to axis of casting. © 2016 Elsevier Ltd Source

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