| Abstract [eng] |
This thesis uses for the first time a nozzle designed for laser metal deposition technology, the de Laval geometry of which is based on a bicubic parametric curve. With the help of the nozzle, the material particles reach supersonic speed, create a narrow stream of exiting particles and form a metal coating with the help of laser radiation. The developed technology allows not only the formation of metal coatings, but can also be applied to additive manufacturing. The characteristics of the nozzle, using it for additive manufacturing, would allow to ensure a higher resolution of the manufactured objects than the laser metal deposition systems currently on the market. The manufactured nozzle combines laser metal deposition technology and cold spray additive manufacturing technology, which uses supersonic gas flow. The goal of the doctoral work is to develop an advanced technology of laser deposition of metal particles, which would allow the deposition and sintering of metal powder particles and the formation of metal coatings. To achieve this goal, a system based on laser metal deposition technology has been developed, ensuring efficient formation of metal coatings; digital modeling was performed and, based on the obtained results, a de Laval nozzle designed for laser metal deposition technology was designed, manufactured and approved; characterized the chemical and physical properties of the CoCrMo powder used for the experiments, to ensure chemical homogeneity; the influence of laser metal particle deposition process parameters on the quality of the formed coating was determined. The dissertation consists of an introduction, three chapters, a summary of the results, lists of used literature and the author's publications on the topic of the dissertation. The introductory chapter discusses the research problem, the relevance of the work, describes the research object, formulates the purpose and tasks of the work, describes the research methodology, the scientific novelty of the work, the practical significance of the work results, and defensive statements. The first chapter reviews additive manufacturing technology, the main features of laser metal particle deposition technology, powder materials used for this technology and their production methods, and material feeding in the system. At the end of the chapter, conclusions are formulated and the tasks of the dissertation are clarified. The second chapter describes the materials and equipment used for the experiments, the methodology, the parameterization of the De Laval nozzle geometry, and the methods of studying the properties of the materials used in the work. The third chapter presents and analyzes the results of the numerical simulation of the De Laval nozzle, the tests and results of the CoCrMo powder used for the experiments, describes the experimental development of the laser metal particle deposition technology and the results of the investigation of the coatings formed with the help of the nozzle. The results of the dissertation are presented in 2 scientific articles, which are in the publications of the Clarivate Analytics Web of Science database. Research results have been published at 7 international scientific conferences in Lithuania. |
