Materiāla virsmas atjaunošanas tehnoloģiju analīze un lāzeruzkausēšanas tehnoloģiju pētījumi
Summary of the Doctoral Thesis
Andris Ratkus, Riga Technical University, Latvia
With the development of metal coating renovation technologies, such as laser cladding, to make them more accessible and more flexible, the interest of manufacturers in these technologies is increasing. This has led to the need for new and specialized, technology-driven research which enhances the technology’s potential for renewal and repair of materials and has made the technology more mainstream across a wider swathe of industries. Based on these industrial activities and the need for modification of metal coatings, a doctoral thesis has been developed with the theme: “Analysis of Material Surface Renewal Technologies and Research of Laser Cladding Technology”.
The aim of the thesis is to clarify the influence of technological parameters and conditions on the characteristics of the coating obtained and to develop the mathematical expression for predicting the characteristics of the technologies for creating a layer of material. In addition, the following tasks have been defined: to undertake cladding experiments and analysis of the results by determining the dependence of the laser cladding characteristics on the cladding position and nozzle angle; to test the hardness of the coating and to determine the factors affecting the hardness in laser cladding; to give recommendations on the practical application of the technology for the restoration of both external and internal surface materials.
The analysis of the technology for applying layers of material, the identification of the most important characteristics of the cladding, the development of experiments and the analysis of the results were performed in this work. It has been determined that the main technological advantages of quality and universality of products are achieved by means of laser cladding, which makes it possible to create small, local cladding. It has been assumed that the characteristics of the coating largely depend on the amount of material conveyed to the coating area which, in turn, is affected by the material feed rate and the speed of cladding. It has been experimentally confirmed that laser cladding technology is possible for all cladding positions, but the change of the position of the cladding, along with the nozzle angle, affects the flow of the material and the power intensity, which causes changes in the geometry of melt pool and affects the values of the coating characteristics, including its mechanical qualities. The hardness values of the laser coated materials have been determined and it was concluded that the nozzle angle, nozzle position, the shape of the laser point, the degree of coalescence of the cladding and the melt pool temperature all influence the hardness values of the cladding. In turn, the distribution of the temperature of the melt pool describes the nature of the hardness values of the cladding profile. Mathematical expressions have been developed in this work, to describe the characteristics of the laser cladding, with the introduction of a new laser cladding impact parameter that includes all the technological parameters used. The developed mathematical expression significantly improves the predictability of the technology and its application in production, in order to shorten the time of operation and improve the quality of the product. The results obtained are important for more extensive research and development in the field. The work provides valid recommendations for the practical realization of cladding.
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