1) Wider Research Context
Transition metal borides (TMBs) are a highly promising material family for functional coatings due to their abundance and cost-effectiveness. They exhibit exceptional mechanical properties, including a high melting point, hardness of up to 60 GPa, and outstanding resistance to corrosion and wear. Moreover, TMBs exhibit unique self-lubricating properties through the formation of metal and boron oxide layers – via boric acid formation at low temperatures and boron oxide at elevated temperatures. However, the fundamental lubrication mechanism of boron oxide, particularly in thin films, remains poorly understood. Physical Vapor Deposition (PVD) technology, with its capability to tailor material properties, offers a versatile platform to investigate ceramic TMBs, enabling a deeper exploration of their self-lubrication properties.
2) Research Questions
This project aims to address critical gaps in understanding the fundamental formation and behavior of boron oxide in TMB thin films for solid self-lubrication. The objectives are:
i. To study how environmental factors, such as atmosphere, humidity, temperature, and stoichiometry, affect the formation of boron oxide of TMB in tribological contacts.
ii. To investigate the mechanochemical processes driving potential phase changes in boron oxide and their impact on lubrication properties.
iii. To evaluate the tribological performance of TMB thin films under varying conditions, including changes in atmosphere, temperature, pressure, stoichiometry, and residual stresses.
3) Methods
A multidisciplinary approach will be employed to achieve the project objectives. Experimental methods will include variations in PVD techniques, tribometry, and advanced in-situ analysis to monitor boron oxide formation and phase transitions. In-situ detection of boron oxide will be realized with techniques like XRD, Raman spectroscopy, or nanobeam diffraction at DESY. Additionally, state-of-the-art characterization techniques will be employed, including APT, SEM, (S)TEM, ERDA, XPS, ToF-SIMS, and AFM.
4) Level of Originality
This research aims to advance fundamental understanding of boron oxide's formation and lubrication mechanisms in TMB thin film coatings. The project addresses a significant knowledge gap regarding the mechanochemical transition of B2O3 from amorphous to crystalline states, which could profoundly influence lubrication behavior. By integrating in-situ analysis with tribometry, this study will generate novel data on boron oxide structure and performance, offering insights with applications in extreme wear environments.
5) Primary Researchers Involved
The PI is Ass. Prof. Dr. Helmut Riedl (group leader, Applied Surface and Coating Technology/E308-01-2, TU Wien) overseeing the project along with Univ. Prof. Dr. Carsten Gachot (Head of the Tribology research unit, TU Wien). This interdisciplinary approach involving both research areas is essential to tackle the suggested project.
