Optimizing Surface Texturing for YSZ Thermal-Barrier-Coating on Inconel 718 Substrate to Mitigate High Stresses/Strains; How the Rise of Thermal Barrier Coating Technology Transformed the Aerospace Industry

Introduction

High temperature material systems often require thermal barrier coatings (TBCs) with low thermal conductivity to protect components from heat damage. TBCs are generally composed of a ceramic material, such as yttria-stabilized-zirconia, and are deposited onto a substrate with an intermediate ‘bond coat’ to ensure proper adhesion. Working in a lab at the University of Virginia that involves the chemical synthesis of ceramic-based TBC materials sparked an interest for this technology. Therefore, the STS research paper and technical project focus on TBCs, exploring the significance and impact TBCs have made in the aerospace industry throughout the years, how they are continuing to be improved in current research, and analyzing how TBC adhesion and performance can be improved through texturing the bond coat.

Capstone Project Summary

The goal of the technical project is to investigate how varying surface texture variables of a TBC system, including texturing method, geometry, and depth, can be leveraged to improve adhesion and performance in high temperature environments. The team selected three distinct textures designed to induce dense vertical cracking (DVCs) and mitigate spallation after differential thermal expansion at high temperatures: rounded spikes, grid pattern, and grown columns. Samples were created with each of these textures using an ultra-short pulsed lasering technique, along with the industry standard grit blast as a control. The team performed testing to understand coating system behavior in response to the high temperature and stress environments these coatings are designed for — including thermal cycling testing, accelerated thermal cycling testing, and adhesion testing.

Adhesion testing results indicate all textures produced increased mechanical interlocking as compared to the industry standard grit blast samples. Despite thermal cycling testing resulting in far lower coating lifetimes than Rolls-Royce had expected for all textures, the team has identified ways to avoid this in the future: adjusting spray parameters and ensuring the preservation of the bond coat. Microstructural and compositional analysis reveals the potential for these textures to induce controlled, periodic DVCs. In the future, the team hopes that these results can inform the next iteration of texture testing using improved coating system parameters.

STS Research Paper

The STS research paper focuses on the application of thermal barrier coating (TBC) systems in aerospace engineering, answering how the rise of TBCs have transformed the aerospace industry over the years and what current advancements are being made to improve its adhesion and performance. This paper will dive into the history of TBCs from when issues with high temperature systems emerged and when TBCs were first developed, to when research on TBC materials became more widespread. It will then explore current research being conducted to improve TBCs even further. The Social Construction of Technology (SCOT) framework will be applied to analyze how the performance demands and environmental concerns of different social groups have driven and continue to drive advancements in TBC systems. These groups include engineers, manufacturers, and consumers.

Through a review of industry reports, technical literature, and interviews with materials scientists from Rolls Royce and CCAM, this paper will illustrate how technological improvements in TBCs are negotiated among social actors. It will ultimately highlight the relationship between engineering advancements and societal needs, showing that the evolution of technologies like TBCs are not solely driven by technical necessity. More specifically, it will show how TBCs have not only provided a longer lifespan for high temperature systems such as turbine engines and combustion chambers, but has and continues to be developed more sustainably, efficiently, cost effective, etc., to better meet demands of the social groups involved.

Concluding Reflection

Working on both the STS research paper and Capstone project provided more understanding on the function and performance of TBCs, especially after learning about and contributing towards current research being done to improve TBC adhesion and lifetime. They provided different angles on the technology, with one grounded in experimental engineering and one on the socio-technical context. Understanding the historical and industrial significance of adhesion challenges in aerospace gave more depth to the technical decisions made in the lab. Conversely, working with the physical properties of TBCs at the micro-level allowed for a greater appreciation for the complexities engineers face when designing for extreme environments. This dual perspective strengthened the ability to think critically about innovation—not just how it works, but why it matters.

School of Engineering and Applied Science
Bachelor of Science in Materials Science and Engineering
Technical Advisor: James Fitz-Gerald
STS Advisor: Bryn Seabrook
Technical Team Members: Nicolas Fonseca Alva, Lara Ojha, Alice Pandaleon, Christopher Recupero