Publicação
Tribology Behaviour in High-performance Coatings for Bike Chains Deposited by PVD
| Resumo: | The rising popularity of cycling worldwide, driven by health, environmental, and sustainability reasons, underscores the growing demand for high-quality bike components. Among these components, bike chains are one of the most crucial part, requiring good mechanical and tribological properties to meet the needs of cyclists. However, despite enhancing bike chain performance, hard chromium coatings, pose significant environmental and health risks due to the extensive release of Cr (III) and Cr (VI) ions into the environment, leading to the search for safer alternatives. This thesis work proposes the development of ZrCN coatings as a possible substitute for hard chromium, deposited via magnetron sputtering as a Physical Vapor Deposition (PVD) technique. ZrCN coatings with increasing carbon content were successfully deposited and comprehensively evaluated for their mechanical and tribological performance. Basic characterization of the coatings was also conducted, including morphology, structure, hardness, Young’s modulus, etc., using several advanced characterization techniques such as SEM, EDS, and XRD. It was observed that the carbon content increase in the coatings led to their amorphization and increase in compactness. The mechanical properties were also progressively decreased with the carbon amount in the coatings, with the reference coating ZrN showing the highest hardness value (25 GPa). The coatings underwent tribological characterization in dry and oil-lubricated conditions using pin-on-disc sliding tests. Dry tribological tests revealed that the coating with the highest carbon content (ZrN 75C) exhibited the lowest coefficient of friction among all samples tested, also demonstrating superior wear resistance with a specific wear rate of 1.46 × 10-15 m3/Nm. In contrast, reference ZrN coating showed the highest coefficient of friction and wear rate, correlating with the significant abrasive and adhesive wear observed in the wear track. Under oil-lubricated conditions, all samples exhibited similar and very low coefficients of friction and no wear was possible to be calculated, indicating that the oil provided an effective lubrication and that the contact was occurring in an hydrodynamic regime. These findings allow to infer that certain ZrCN coatings can be proposed as a promising environmentally friendly and similar or high-performance alternative to traditional chromium coatings to prolong the lifetime of bike chains. |
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| Autores principais: | Ahmed, Toukir |
| Assunto: | Coatings deposition ZrCN coatings Physical vapor deposition Tribology Deposição de revestimentos Revestimentos ZrCN Deposição em fase de vapor Tribologia |
| Ano: | 2024 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Coimbra |
| Idioma: | inglês |
| Origem: | Estudo Geral - Universidade de Coimbra |
| Resumo: | The rising popularity of cycling worldwide, driven by health, environmental, and sustainability reasons, underscores the growing demand for high-quality bike components. Among these components, bike chains are one of the most crucial part, requiring good mechanical and tribological properties to meet the needs of cyclists. However, despite enhancing bike chain performance, hard chromium coatings, pose significant environmental and health risks due to the extensive release of Cr (III) and Cr (VI) ions into the environment, leading to the search for safer alternatives. This thesis work proposes the development of ZrCN coatings as a possible substitute for hard chromium, deposited via magnetron sputtering as a Physical Vapor Deposition (PVD) technique. ZrCN coatings with increasing carbon content were successfully deposited and comprehensively evaluated for their mechanical and tribological performance. Basic characterization of the coatings was also conducted, including morphology, structure, hardness, Young’s modulus, etc., using several advanced characterization techniques such as SEM, EDS, and XRD. It was observed that the carbon content increase in the coatings led to their amorphization and increase in compactness. The mechanical properties were also progressively decreased with the carbon amount in the coatings, with the reference coating ZrN showing the highest hardness value (25 GPa). The coatings underwent tribological characterization in dry and oil-lubricated conditions using pin-on-disc sliding tests. Dry tribological tests revealed that the coating with the highest carbon content (ZrN 75C) exhibited the lowest coefficient of friction among all samples tested, also demonstrating superior wear resistance with a specific wear rate of 1.46 × 10-15 m3/Nm. In contrast, reference ZrN coating showed the highest coefficient of friction and wear rate, correlating with the significant abrasive and adhesive wear observed in the wear track. Under oil-lubricated conditions, all samples exhibited similar and very low coefficients of friction and no wear was possible to be calculated, indicating that the oil provided an effective lubrication and that the contact was occurring in an hydrodynamic regime. These findings allow to infer that certain ZrCN coatings can be proposed as a promising environmentally friendly and similar or high-performance alternative to traditional chromium coatings to prolong the lifetime of bike chains. |
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