Author, Institution: Lukas Bastakys, Kaunas University of Technology
Science area, field of science: Technological Sciences, Materials Engineering, T008
Research supervisor: Prof. Dr. Liutauras Marcinauskas (Kaunas University of Technology, Natural Sciences, Physics, N002)
Research consultant: Assoc. Prof. Dr. Brigita Abakevičienė (Kaunas University of Technology, Natural Sciences, Physics, N002)
Dissertation Defence Board of Materials Engineering Science Field:
Prof. Dr. Hab. Arvaidas Galdikas (Kaunas University of Technology, Technological Sciences, Materials Engineering, T008) – chairperson
Senior Researcher Dr. Mindaugas Andrulevičius (Kaunas University of Technology, Technological Sciences, Materials Engineering, T008)
Prof. Dr. Sergejs Gaidukovs (Riga Technical University, Latvia, Technological Sciences, Materials Engineering, T 008)
Prof. Dr. Juozas Padgurskas (Vytautas Magnus University, Technological Sciences, Mechanical Engineering, T009)
Prof. Dr. Valdas Šablinskas (Vilnius University, Natural Sciences, Physics, N 002)
Dissertation defence meeting will be at Rectorate Hall of Kaunas University of Technology (K. Donelaičio 73-402, Kaunas)
The doctoral dissertation is available at the library of Kaunas University of Technology (Gedimino 50, Kaunas) and on the internet: L. Bastakys el. dissertation.pdf
© L. Bastakys, 2026 “The text of the thesis may not be copied, distributed, published, made public, including by making it publicly available on computer networks (Internet), reproduced in any form or by any means, including, but not limited to, electronic, mechanical or other means. Pursuant to Article 25(1) of the Law on Copyright and Related Rights of the Republic of Lithuania, a person with a disability who has difficulties in reading a document of a thesis published on the Internet, and insofar as this is justified by a particular disability, shall request that the document be made available in an alternative form by e-mail to doktorantura@ktu.lt.”
Annotation: The phase structure and tribological properties of chromium oxide and chromium oxide-based composite coatings deposited by plasma spraying were investigated. The study evaluates the effects of air-hydrogen plasma flow composition, temperature, and graphite as well as titanium oxide-silicon oxide additives on the elemental composition, phase structure, and tribological properties of chromium oxide coatings under dry sliding conditions. It was demonstrated that using a solid lubricant, such as graphite, which is passably economical in comparison to other carbon-based nanomaterials, a novel tribologically efficient Cr₂O₃-graphite and Cr₂O₃-TiO₂-SiO₂-graphite coatings with improved friction coefficients and low specific wear rates were formed. An increase in plasma flow temperature was shown to intensify graphite oxidation and sublimation, resulting in a reduced graphite concentration in the coatings. Raman spectroscopy investigations revealed the formation of a graphite self-lubricative tribolayer on the coating surface, while the tribological effectiveness of this graphite layer depended on the applied load during testing. It was demonstrated that the incorporation of additives such as graphite or/and TiO₂-SiO₂ into Cr₂O₃ coatings, combined with appropriate plasma spraying conditions, can reduce the friction coefficient of the coatings up to 40 % and enhance wear resistance of coatings by a factor of two. By selecting suitable additives and plasma spraying parameters, highly wear-resistant chromium oxide composite coatings were produced, exhibiting a specific wear rate up to 45 times lower than that of steel. Furthermore, the study proposed a technological solution involving the use of air instead of argon or nitrogen as the plasma-forming gas, which reduced the cost of the plasma spraying process while simultaneously improving the tribological properties of the deposited coatings.