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Work has concluded on the development and corrosion testing of thin, metallic coatings on Mg alloy substrates obtained via combined magnetron sputtering and arc vapor deposition. The two methods are classified as physical vapor deposition (PVD) techniques and are widely used for coating different kinds of substrates with thin layers of functional metals. Recent technological advancements allow for the deposition of ceramics as well by means of in-situ addition of various ceramic forming species, such as nitrogen and hydrogen. This work has utilized all the recent technological advancement and innovative methods to obtain multicomponent PVD coating on Mg substrate.
The coatings were multicomponent in nature, consisting of a combination of Titanium (Ti), Aluminium (Al), Silicon (Si) and Niobium (Ni) that enhance its structural and corrosion resistance properties. A specimen with nitride surface was included as well to test the efficacy of ceramic coating. Preliminary work consisted of surface preparation for the deposition process by means of ion bombardment of the part. Removal of the thin oxide layer that form on the part due to exposure to the oxygen in air is necessary to ensure maximum adhesion of PVD coating. Then, application of the two PVD processes was performed to obtain thin (<1 um thickness) coatings. Rigorous corrosion testing of the specimens (70 h total, 2 h cycles in 5% NaCl solution) reveal that the coating with all 4 components perform the best among all the different coatings. After prolonged exposure to the saline solution, parts of the surface were still shiny, and the damage was localised in the substrate. This method shows tremendous promise in developing corrosion resistant coatings for Mg alloys.
SEM micrographs of PVD coating consisting of Al-Ti-Si-Nb (left) and Al-Ti-Nb (right)
Being implemented with the financial support of the ERDF.