Prof. Silvia Maria Deambrosis

National Research Council of Italy - Institute of Condensed Matter Chemistry and Technologies for Energy, Italy
Silvia Maria Deambrosis received her degree in Material Science from the University of Padova, Italy, in 2004. In 2008 she earned her PhD in Material Science and Engineering at the same University. Since 2010 she works as researcher at the National Research Council of Italy (CNR) - Institute of Condensed Matter Chemistry and Technologies for Energy (ICMATE). She is the Head of Advanced Coatings Research at CNR-ICMATE since 2011. Her main expertise are: deposition of functional films via Physical Vapor Deposition (PVD) - Magnetron Sputtering technologies; morphological, compositional and microstructural characterizations of materials (bulk and coatings); mechanical, tribological and tribo-chemical analyses.

Talk title: High entropy alloy protective coatings via magnetron sputtering technology
Physical vapor deposition (PVD) technologies have emerged as a versatile and effective solution for growing HEA thin films, offering precise control over their composition, thickness, and overall quality. Therefore, understanding the influence of the process parameters is essential for tailoring the structure and properties of PVD-deposited HEA coatings to meet specific application requirements. Concerning the research work recently done at the Institute of Condensed Matter Chemistry and Technology for Energy (National Research Council of Italy, CNR-ICMATE) on this hot topic, CoCrFeNi-based films were deposited on Si (100) and AISI 304 stainless steel substrates by high-power impulse magnetron sputtering (HiPIMS). Initially, Mo was introduced as a fifth element, and its influence on the microstructure, mechanical properties, and corrosion/tribocorrosion behavior of the films was investigated by adjusting the Mo target-to-substrate distance. All films exhibited a columnar growth morphology with a high density of planar defects. Increasing the Mo content resulted in a transition from a face-centered cubic (FCC) structure to a two-phase FCC + body-centered cubic (BCC) structure, resulting in reduced grain size and increased hardness. While the corrosion resistance of the films in a 3.5 wt.% NaCl aqueous solution showed no significant variations, the tribocorrosion behavior deteriorated at higher Mo concentrations. Building upon these findings, (CoCrFeMo_0.5Ni)_1−xN_x coatings were synthesized by introducing N₂ during deposition. The incorporation of nitrogen not only enhanced the hardness of the films but also significantly improved their wear and corrosion performance. Then, Mo was replaced with Al, and Al_xCoCrFeNi films were deposited at various bias voltages. Higher bias voltages promoted the formation of a dense, featureless structure, positively affecting the electrochemical performance of the films. Simultaneously, the residual stress state within the coatings shifted from tensile to compressive due to the intensified ion bombardment effect at higher bias voltages. Nevertheless, the hardness of the films remained relatively constant. Differences were found, however, in terms of tribocorrosion behavior, with the wear rate exhibiting a non-linear trend with increasing bias voltage. These results aim to promote to a comprehensive understanding of the interplay between the synthesis, microstructure, and properties of HEA coatings, offering effective insights for optimizing their performance in wear and corrosion-prone applications.