Studium ovlivněných vrstev materiálu při obrábění leteckých superslitin laserem

Abstract

Dissertation thesis is focused on the laser beam machining process, specifically on a study of laser beam machined features of super alloys. The effect of laser beam machining/drilling on mechanical properties of Inconel 718 is investigated mainly with emphasis on undesirable recast layer on the feature surface as a result of the process. Although the object of investigation is Inconel 718 nickel superalloy the thesis devotes in its theoretical part to others common nickel, iron, cobalt and titanium based superalloys. By that, the comprehensive view of the use of these materials in current technical applications is unified. Theoretical part of the thesis also describes in detail knowledge of laser technology, historical development of laser, its principle, construction and classification of lasers. Briefly, the advantages and disadvantages of some typical applications of laser technology in mechanical engineering are discussed e.g. laser cutting, drilling, welding, etc. The issue of affecting of the laser beam machined material, qualitative aspects as well as process parameters of laser beam machining are read up in detail. Experimental part of the thesis is focused on a static uniaxial tension test at room temperature (23 °C) as well as at elevated temperature (550 °C). Flat shape experimental samples have been made of Inconel 718 material with 0,5 mm, 1,0 mm and 1,6 mm thicknesses and all the samples have also been heat treated. Subsequently, one hole with 0,8 mm diameter in the middle of the length of all drilled samples has been drilled under the 70 ° degree by drilling tool and by laser beam with different parameters as well. All types of drilled holes have been metallographically evaluated so the average thickness of recast layer and the length of microcracks have been measured. Finally, all the samples have been evaluated by tensile testing. From the results of the experimental works the particular dependencies of mechanical properties of Inconel 718 material can be determined based on the created recast layer which is closely associated with the used laser drilling process parameters. The effect of change of testing temperature on the mechanical properties of the material is established for all the circumstances of individual experiments.