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Title:A Study of Reduced Chromium Content in A Nickel-Base Superalloy via Element Substitution and Rapid Solidification Processing
Author(s):Powers, William Owen
Department / Program:Metallurgy and Mining Engineering
Discipline:Metallurgical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Engineering, Metallurgy
Abstract:A study of reduced chromium content in a nickel-base superalloy via element substitution and rapid solidification processing was performed. The base alloy studied was a commercial nickel-based superalloy, 713LC, which was developed by the INCO family of companies. The two elements used as partial substitutes for chromium were Si and Zr.
The microstructure of conventionally solidified materials (713LC, 713LC + 1.0 Si, 713LC + 1.0 Zr, 713LC - 1/2 Cr + 1.0 Si, and 713LC - 1/2 Cr + 1.0 Zr (wt.%)) was characterized using light optical microscopy (LOM), scanning electron microscopy (SEM), and analytical electron microscopy (AEM). These alloys were rapidly solidified using the chill block melt spinning technique and the rapidly solidified microstructures were characterized using AEM. The thermal stability of the rapidly solidified microstructures was assessed following heat treatments at 1033 K and 1273 K.
Rapidly solidified material of three of the alloys (713LC, 713LC - 1/2 Cr + 1.0 Si, and 713LC - 1/2 Cr + 1.0 Zr) was reduced to particulate form and consolidated using hot isostatic pressing (HIP). The consolidated materials were also characterized using LOM, SEM, and AEM. In order to evaluate the relative strengths of the consolidated alloys, compression tests were performed at room temperature and 1033 K on samples of as-HIP'ed, and HIP'ed plus solution treated material. The yield strengths of the alloys 713LC and 713LC - 1/2 Cr + 1.0 Zr were similar; however, the yield strengths of the alloy 713LC - 1/2 Cr + 1.0 Si were significantly lower in comparison with the other two alloys. This was primarily attributed to either larger grain sizes, higher porosity levels, or larger amounts of prior ribbon boundary precipitation in the HIPs of the alloy 713LC - 1/2 Cr + 1.0 Si, or a combination of these factors.
The oxidation resistance of the HIP'ed materials, as well as some conventionally solidified materials, was investigated using isothermal and cyclic tests at 1373 K. In general, the oxidation resistance of the alloys 713LC and 713LC - 1/2 Cr + 1.0 Si were similar. However, the oxidation resistance of the alloy 173LC - 1/2 Cr + 1.0 Zr was significantly worse in comparison with the other materials. The oxidation mechanisms leading to the variation in oxidation resistance of the materials were not explicitly determined in this study.
Issue Date:1987
Description:292 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1987.
Other Identifier(s):(UMI)AAI8711854
Date Available in IDEALS:2014-12-16
Date Deposited:1987

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