| Laser cladding technology has the advantages of high input energy,controlled heat range and high molding quality,which has a promising future in the field of surface modification.Laser cladding technology is influenced by a number of factors and the quality of the laser cladding layer can be improved by adjusting the process parameters.Therefore,it is important to obtain the optimal combination of process parameters for the laser cladding layer.In this paper,nickel alloys are fused to nodular cast iron and the range of process parameters is determined by numerical simulation of thermal stresses,then obtain the optimal combination of process parameters by orthogonal tests and microscopic verification.The main research contents in this paper are as follows:(1)Numerical simulation of nickel alloy laser cladding thermal stress field threedimensional model was established in ANSYS Workbench software,the material properties are imported,the cell type is selected and the mesh is divided,the Gaussian heat source is selected,initial and boundary conditions are added,then the temperature field is modeled.Temperature loads and fixed supports are loaded into the stress field model to complete the stress field modeling.(2)Numerical simulations of the laser cladding temperature field were carried out in Workbench with multiple groups,and the control variable method was used to analyse the influence mechanisms of different process parameters such as laser power,scanning speed,spot diameter and powder feeding rate on the maximum temperature and morphological structure of the melt pool.Thus the combination of process parameters was optimised through the obtained changing rule of laser cladding temperature field,which provides theoretical guidance for the optimisation of the experimental process parameters.(3)Numerical simulations of the stress field of nickel alloy laser cladding were carried out by introducing the thermal load in the temperature field into the stress field in order to obtain the distribution and numerical changes of the three axial stresses in different paths and to provide theoretical guidance for the defect generation mechanism.The influence of laser power,scanning speed,spot diameter and powder feeding rate on the maximum residual stress in the stress field is analysed,and the optimal combination of process parameters in the numerical simulation process is obtained in combination with the temperature field variation law to provide reference for the selection of test parameters.(4)Based on the combination of process parameters obtained from numerical simulation,an orthogonal test table is designed.First,the mean response with width,height and dilution rate were analyzed under the interaction of different process parameters.The parameters of the main factors affecting the temperature and stress fields and their variation patterns are obtained and the simulation model is validated.Second,the mean responses of different process parameters interacting with aspect ratio and dilution rate were analyzed,The optimal combination of process parameters was obtained as laser power of 1 k W,scanning speed of 12.5 mm/s,spot diameter of 3 mm,and powder feeding rate of 22 g/min which through constructing and plotting the equivalence curves of the three factors.Then the specimens are made again to verify the accuracy of the optimal combination of process parameters by microscopic testing.This paper established a three-dimensional model of the thermal stress field of nickel alloy laser cladding,which can correctly and effectively simulate the temperature and stress fields in the laser cladding process under different combinations of process parameters,which provides theoretical guidance for the selection and optimization of the test parameter range.More accurate and reliable optimal process parameter combinations were obtained through orthogonal tests and the results were microscopically verified,which is an important guideline for obtaining the optimal process parameter combinations for laser cladding. |
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