Abstract
My Thesis Project Portfolio is comprised of both my technical report and STS research paper. The former walks through my technical capstone for the fulfillment of the Materials Science and Engineering department in which my group collaborated with Rolls-Royce Corporation on the effect of interface contamination in 304 stainless steel. The latter investigates the history of a specific technology, the single-crystal turbine engine blade, and explores its sociotechnical context through the lens of technological diffusion.
My technical project investigated the role that interface contamination plays in adhesion efficacy, specifically within the aerospace context. With Rolls-Royce Corporation, PulseTex, and the Commonwealth Center for Advanced Manufacturing (CCAM), my team correlated adhesion performance with differing levels of interface contamination and surface roughness, functionalized through grit blasting. Grit blasting is a common manufacturing process to improve coating adhesion on an aerospace engine component by enabling good mechanical interlocking through surface texture. Despite its speed and cost-effectiveness, however, grit blasting can often result in interface contamination of grit blast media, the extent of which is dependent on variables such as substrate material, grit media material and size, and grit blast parameters (e.g. standoff distance, angle, and pressure). Understanding the direct relationships between grit blasting parameters and interface contamination, and subsequent adhesion effects is crucial to setting appropriate interface contamination limits. Laser surface modification can potentially help to remove this interface contamination without detrimentally impacting surface roughness, substrate chemistry, microstructure, and function performance. The goal of this project is to design an engineering platform to examine the impact of grit blasting processes to 1) determine the relationship between grit blast media and/or parameters on resulting surface roughness, interface contamination, and adhesion, and 2) determine if a laser can be used to reduce the amount of interface contamination while maintaining acceptable surface roughness and adhesion. In the preliminary phase of the project, the team created a 3x3 matrix of grit blasting parameters – three levels of both standoff distance (4, 6, 8 inches) and blast pressure (30, 45, 60 psi) – to down-select three combinations of parameters to maximize the range of interface contamination and surface roughness for the secondary phase. These three combinations then progressed into the secondary phase in which 6 parameter sets – Combination 1, Combination 2, Combination 3 with no laser processing, Combination 3 with aggressive laser parameters, Combination 3 with middle laser parameters, and Combination 3 with gentle laser parameters – underwent bond coating and adhesion testing in accordance with ASTM C633 to extrapolate the effects of interface contamination, surface roughness, and laser parameter set on adhesion performance.
My sociotechnical paper explores the development and use progression of the singlecrystal turbine engine blade and argues how the diffusion of the technology follows the S-curve of a logistic function modeled and identified in Paul Geroski’s “Models of Technology Diffusion.” This curve tells of a slow period of early take-up followed by a phase of rapid adoption and finally a gradual approach to saturation. I discuss how single-crystal blade technology became the “industry standard” that it is today, following the initial pioneering by Pratt & Whitney and the subsequent rapid adoption by airplane manufacturers, and how that closely models the logistic framework established by Geroski. I argue how the technology reflects the modern industry standard by discussing the economic benefits imbued to Pratt & Whitney through the first half of the diffusion curve and how modern innovation in this sector focuses on alloy development with the underlying assumption of single-crystal technology. I present my argument through archival research, collecting technical and sociotechnical papers and articles surrounding the topic. Archival research specifically helps me to reconstruct timelines and establish connections between stakeholders while also maintaining a mix of primary sources from manufacturers and researchers and secondary sources removed temporally and/or technically.
Though separate in their scope and specific focus, both projects fall within the fields of aerospace and materials science. I chose the STS topic that I did in order to look more in depth at a renowned materials science innovation from a sociotechnical perspective. Single-crystal turbine engine blades are the prime intersection of materials science and aerospace. A technology that revolutionized air travel and afforded great energy and cost cuts for the aerospace industry, single-crystal turbine engine blades would not have been possible without intense research and innovation within the field of materials science to develop appropriate methods of manufacturing and alloying. My technical project falls squarely in a similar realm. Adhesion failure within components inside of an airplane engine is catastrophic to the whole. While single-crystal turbine engine blades work to increase efficiency and reliability, proper adhesion and interface contamination research work to protect from premature component failure within the engine.
