Temperature Field Simulation Of Dual-beam Cladding Al₂O₃and Design Of Optical System

With the development of industrial technology, conventional materials can barely use in some special situations. But manufacture of high-performance material component is very difficult. It has a very significant meaning for the development of industrial technology for fabricating high-performance coatings on the components. Technology of laser cladding has huge potential for fabricating high-performance coatings. Al2O3ceramic has a high fusion point, high rigidity and intensity, has been widely applied in some special fields such as aerospace. Manufacture of high-performance Al2O3ceramic coating on surface of components can improve ability of components such as hardness, rub resistance and corrosion resistance. However, Al2O3ceramic is fragile and cannot suffer thermal shock. In the process of laser cladding Al2O3ceramic coatings, huge temperature gradient on the coating causes large thermal stress which makes the coating crack. So reduction of temperature gradient in the process of laser cladding has a significant meaning to fabricate high quality Al2O3ceramic coatings. In order to reduce the temperature gradient during laser cladding, technology of dual-beam laser cladding based on theory of preheating and slow-cooling is proposed in this paper. During the process of the cladding by fabricating beam (main beam), an assistant laser beam is applied to provide preheating and slow-cooling. The temperature field finite element model of dual-beam laser cladding Al2O3ceramic coating is established through ANSYS. Regularity of temperature field distribution by dual-beam laser cladding is analyzed; research of the influence of temperature and temperature gradient with dual-beam laser cladding is done. Beam shaping method of assistant beam is determined; energy distribution of assistant beam is optimized and assistant beam optical system that satisfied system requirement is designed. Specific studies are as follows:(1) Depending on the requirement of the dual-beam laser cladding system, analyze different kinds of beam shaping technology; determine assistant beam shaping method; through analysis of mathematic model of the energy distribution of the assistant beam, the energy distribution regularity of assistant beam is determined;(2) The model of dual-beam laser cladding Al2O3ceramic coating is established through ANSYS, regularity of temperature field distribution is analyzed; reduction of temperature gradient using assistant beam preheating and slow-cooling is verified; influence of temperature distribution with different spot sizes, power density and energy distribution of assistant beam are discussed, optimized energy distribution of assistant beam is acquired;(3)Design the aspheric lens for assistant beam shaping, use surface function of the aspheric lens to fit and optimize the aspheric lens surface function; acquire aspheric lens that satisfied design requirement; different shape and different energy distribution is realized; design other optical components of the assistant light path.