The Influence of Shell Mold Composition on the As-cast Macro- and Micro-structure of Thin-Walled IN713C Superalloy Casti
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JMEPEG (2019) 28:3974–3985 https://doi.org/10.1007/s11665-019-04098-9
The Influence of Shell Mold Composition on the As-cast Macro- and Micro-structure of Thin-Walled IN713C Superalloy Castings Łukasz Rakoczy, Małgorzata Grudzien´-Rakoczy, and Rafał Cygan (Submitted September 28, 2018; in revised form February 21, 2019; published online May 23, 2019) In the investment casting process, the building of ceramic layers around the wax pattern is the main timeconsuming stage. Increasing their number ensures sufficient mechanical properties, but also lengthens the whole process, including drying time and preheating of the mold. Four molds for casting Ni-based superalloy IN713C were strengthened by glass fibers, included in the slurry, and metal powder, of Al, Cu, Fe or Ni, in the coverage. Castings were subjected to microstructural investigations in order to find out if the new design can be promising for the manufacture of jet engine components. Bend tests revealed that the green strengths of all new molds were higher, at least 3.65 MPa, than that of the unmodified molds, 3.0 MPa. Optical microscopy revealed that the composition of a mold had a strong influence on stereological parameters of equiaxed IN713C grains. Microstructural observation and hardness measurements of castings revealed differences in the volume fraction of strengthening phases, porosity and hardness. The microstructure due to the complex chemical composition of IN713C consisted of several phases including ternary eutectics as a consequence of L fi c + Ni7Zr2 + (Nb, Zr)C. Keywords
aviation, glass fibers, investment casting, metal powder, shell mold
1. Introduction Ni-based superalloys are characterized by high mechanical strength and resistance to creep at high temperatures, which is ensured by their complex chemical composition, microstructure and technological process. One of these alloys is precipitationstrengthened Inconel 713C which possesses excellent strength up to 980 C (Ref 1-4). It is widely used for rotating and nonrotating components, namely low-pressure turbine blades and vane clusters in the new generation aircraft jet engines GP7200 (Ref 5, 6). The complex geometry of these components effectively does not allow machining. Investment casting (IC) is an extremely important technique for such fabrication because of its ability to obtain complex geometries, dimensionally very accurate, with an excellent surface finish. Taking This article is an invited submission to JMEP selected from presentations at the 73rd World Foundry Congress and has been expanded from the original presentation. 73WFC was held in Krakow, Poland, September 23-27, 2018, and was organized by the World Foundry Organization and Polish FoundrymenÕs Association. Łukasz Rakoczy, Department of Physical and Powder Metallurgy, Faculty of Metals Engineering and Industrial Computer Science, AGH University of Science and Technology, Av. Mickiewicza 30, 30-059 Cracow, Poland; Małgorzata Grudzien´-Rakoczy, Lukasiewicz Research Network-Foundry Research Institute, ul. Zakopianska 73, 30-41
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