Date of Award

12-2021

Document Type

Thesis - Open Access

Degree Name

Master of Science in Aerospace Engineering

Department

Aerospace Engineering

Committee Chair

Dr. Sirish Namilae

First Committee Member

Dr. Marwan Al-Haik

Second Committee Member

Dr. David Sypeck

Abstract

In the aerospace industry, there is a desire for increased thermal and mechanical properties of sealing materials. In this thesis, porous Hastelloy-X alloy scaffolds with 80% porosity, currently used for fabricating seals in turbine applications, were used as the base material. The microstructure of the porous Hastelloy-X scaffolds was infiltrated using a room temperature curing silicate colloid (trade name -Dichtol HTWG Hydro #2506) and a novel zirconia based colloid to fabricate the metal matrix composites. Various fabrication processes, some using vacuum and pressure to assist the flow were utilized to infiltrate the scaffolds. The green composites were then cured at the required room or elevated temperature. Composites were characterized using x-ray tomography and scanning electron microscopy (SEM) imaging to analyze the pore infiltration. Rockwell hardness and nanoindentation were measured to determine changes in material properties. Through porosity calculations and SEM imaging, it was determined that vacuum was required for the most effective infiltration. The silicate colloid required a method of drawing the colloid through the scaffold while traditional vacuum was sufficient for the zirconia colloid. Hardness results were influenced by the infiltration method, the method requiring the vacuum to draw the colloid through the scaffold had the greatest increase in hardness. Despite porosity levels, the zirconia composite hardness exceeded the silicate composite at both the Rockwell and nano scale. The mechanism for decrease in plasticity and increase in hardness are examined. The silicate and zirconia composites show better material performance in some areas however, further testing is needed to determine if they are suitable substitutes for the current Hastelloy-X scaffold as a turbine seal.

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