A Study of Reduced Chromium Content in A Nickel-Base Superalloy via Element Substitution and Rapid Solidification Processing
Powers, William Owen
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https://hdl.handle.net/2142/71840
Description
Title
A Study of Reduced Chromium Content in A Nickel-Base Superalloy via Element Substitution and Rapid Solidification Processing
Author(s)
Powers, William Owen
Issue Date
1987
Department of Study
Metallurgy and Mining Engineering
Discipline
Metallurgical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(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.
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