| The research on laser cladding technology in part surface repair is mainly based on horizontal substrates.Due to the complex shape of the actual part to be repaired,the existing research theory of horizontal substrates is not sufficient to support the application of additive manufacturing in the field of inclined surface part repair.In this paper,we use numerical simulation and experiment to study the coupling mechanism of nozzle-powder-substrate in the process of inclined substrate cladding,the evolution of single and multi-pass melt pools and geometric features of inclined substrate cladding,and provide theoretical basis for the control of inclined substrate cladding.The main research contents of this paper are as follows.(1)To investigate the influence law of nozzle working height and nozzle deflection angle on powder flow and powder concentration distribution on the substrate through numerical simulation and experimental verification.Combined with the response surface method to design simulation experiments,fitting the function relationship between the powder feeding voltage,gas flow rate,substrate tilt angle and the powder concentration and powder spot diameter on the tilted substrate,optimizing the combination of parameters with the maximum powder concentration and minimum powder spot diameter on the tilted substrate,and realizing the mutual coupling between nozzle-powder-substrate.(2)On the basis of powder flow field study,we conducted a study on the morphology and metal powder melting and solidification process of inclined singlepass cladding.In order to control the quality of beveled cladding,a mathematical model of the characteristics and process parameters of beveled cladding was established by Taguchi’s orthogonal design method based on the nozzle vertical and substrate tilt cladding method,and the influence of substrate tilt angle,laser power and scanning speed on single-pass cladding was investigated.And derive the equation of oblique heat source,design the oblique heat source scheme based on the response surface method,simulate the melting and solidification process of metal powder using comsol software,and reveal the change trend of melt pool morphological characteristics with process parameters.(3)Based on the test and simulation of oblique single-pass melting,the study of surface quality of oblique multi-pass lap forming was carried out.Experimental comparison study of laser scanning methods including top-down and bottom-up transverse continuous or interval scanning methods.It is proposed to maintain a constant working height between the nozzle and the substrate to be coated and to perform continuous or interval scanning to reveal the influence of different laser scanning methods and lap rates on the surface flatness of the beveled clad coating.The research in this paper helps to expand the application of laser melting technology in the field of complex parts surface repair,improve the powder utilization rate,reduce the cost of laser melting industrial application,and provide theoretical guidance in the practical production of complex parts surface repair or remanufacturing. |
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