Developing materials for applications requiring wear resistance is an ongoing and active field. Additive manufacturing (AM) may provide wear-resistant metallic materials with microstructures that are finer than those produced using conventional manufacturing technologies. Despite this potential, the understanding about the tribological performance of AM-processed metallics is still limited and a deeper understanding is required prior to their implementation in industrial applications. The present thesis aims to reveal the tribological performance of a series of electron-beam powder bed fusion-processed metallics, more specifically, three tool steels (8%, 20% and 25% volume carbides), a cemented carbide (65% volume carbides) and a martensitic stainless steel (22.5% volume carbides) with carbide-rich microstructures. Performance was assessed through microstructural, topographical, and tribological characterisation. Among the AM-processed tool steels, the grade with 20% volume carbides have shown the best friction and wear performance via macro- and micro-scale tribological tests and surface topography mapping. This has indicated a limit where the carbide addition is beneficial to improve the tribological performance. The predominant wear mechanism was oxidation against bearing steel for all carbide-rich tool steels at the macro-scale. An increase in carbide content significantly changed the abrasive mechanism at the micro-scale level. The overall wear and friction performance of the AM-processed cemented carbide was similar to conventionally processed cemented carbides under similar testing conditions. The wear mechanisms changed explicitly depending on the counterbody employed during testing. A friction reduction effect was detected when the cemented carbide slid against alumina, while a reduced wear rate was observed against bearing steel. The order of the wear mechanisms over time was revealed at the micro-scale level through videos from in-situ scratching tests. The characterisation of the martensitic stainless steel indicated that the wear rate was nearly identical with a similarly processed tool steel under low load. Abrasion, oxidation, and three-body abrasion were observed as dominant wear mechanisms against alumina. Furthermore, the stainless steel candidate had a plastically deformed zone identified beneath the wear track using micro-hardness mapping. This research provides a better understanding of the tribological performance of AM-processed tool steels, cemented carbide and martensitic stainless steel as well as recommendations for future research. In a wider context, the tribological understating of these AM-processed metallics contributes to broaden their usage for demanding environments and applications. Further, this work presents characterisation approaches for better understanding the wear performance of materials.
Date of Award | 31 Dec 2022 |
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Original language | English |
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Awarding Institution | - The University of Manchester
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Supervisor | Allan Matthews (Supervisor) & Matthew Roy (Supervisor) |
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- Electron beam melting
- Cemented carbides
- Tool steel
- Martensitic stainless steel
- Plastic deformation
- Additive manufacturing
- Micro-tribology
- Abrasive wear
Tribological performance of additive manufactured metallics with carbide-rich microstructures for wear-related applications
Iakovakis, E. (Author). 31 Dec 2022
Student thesis: Phd