High temperature oxidation kinetics of Ni-based alloys for aero-engine exhaust components

Abstract

This thesis investigates the high-temperature oxidation kinetics of two
nickel-based superalloys produced via additive manufacturing (AM), referred to as
alloy A and alloy B, in comparison to the conventionally cast superalloy MAR-M 247.
The study focuses on oxide scale growth, morphology, and depletion zone development under semi-isothermal conditions at temperatures below 900°C and 1000°C over
exposure periods ranging from 20 to 1000 hours.
Oxidation behavior was analyzed using light optical microscopy (LOM) to characterize oxide and depletion zones, and kinetic parameters were determined by fitting
experimental data to generalized oxidation rate laws. Results indicate that surface
preparation significantly influences oxide scale formation and that AM alloys do not
display distinct oxidation kinetics and morphologies compared to MAR-M 247 in
general. Among the alloys investigated though, there were variations in spallation
behavior and scale stability.
These findings contribute to the understanding of oxidation mechanisms in AM alloys
and provide insight into their suitability for high-temperature aerospace applications,
where material durability and oxidation resistance are critical.

Popular Abstract

Modern jet engines are marvels of engineering but they also create some of the harshest, most aggressive environments any material can face. Temperatures soar, and components are exposed to hot gases that can slowly corrode even the toughest metals. To make engines more efficient and environmentally friendly, we counterintuitively need engines that run even hotter and manufacturers are turning to advanced materials that can take the heat.
This thesis explores how nickel-based superalloys, made using additive manufacturing (industrial 3D printing), hold up in such conditions. These alloys could eventually replace traditional cast materials in critical engine parts like exhaust structures. The big advantage? 3D printing allows for more complex designs, shorter lead times, and less material waste, resulting in better engines and cheaper airplane tickets.
The study compares two printed superalloys with a well-known cast alloy (MAR-M 247). The printed alloys were chosen for their comparative similarity to MAR-M 247 in terms of mechanical stability but they differ from each other in their chemical composition with one containing significantly more chromium. Alloy samples were heated for hundreds of hours to simulate engine conditions, and their surfaces were carefully examined to see how protective oxide layers formed and in some cases eventually failed. Understanding the growth of these oxide layers is important for predicting how well a component will last in an engine. When stable, they protect the metal underneath but when they crack or fall off (a process called spallation), the underlying alloy corrodes much faster, leading to failure of the component.
The results show that while the printed alloys can form protective oxide layers, they don’t all perform as well as traditional alloys. This thesis explores some of the reasons for the differences in oxide scale development with aluminum/chromium content proving to be a major factor affecting oxide scale development. Understanding these differences helps engineers design safer, longer-lasting parts for the next generation of aircraft engines.

• author: Sandberg, Nils
• supervisor: Reine Wallenberg
• organization: Centre for Analysis and Synthesis
• course: KASM10 20251
• year: 2025
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: oxidation, kinetics, nickel-based alloys, additive manufacturing, aerospace applications, materials chemistry
• language: English
• id: 9212327
• date added to LUP: 2025-09-17 10:39:25
• date last changed: 2025-09-17 10:39:25