| Due to the unique advantages in high output,high consistency and standardized production,molds are widely used in mechanical parts.Moulds play an important role in the automotive,aerospace,petroleum,electronics and construction industries.During the service period of the hot work mold,the mold cavity is frequently subjected to cold and heat and bears greater impact force during work,which makes the hot work mold extremely prone to failure.Compared with other mold repair methods,laser cladding has the advantages of low dilution rate,convenient control,accurate positioning and automatic operation,and has become a research hotspot in mold repair methods.However,during the repair process,cracks,slag inclusions,pores,etc.of the cladding layer The defect problem has not been completely resolved.Laser shock forging composite additive manufacturing is a brand-new composite additive manufacturing technology that uses pulsed laser-induced shock waves to perform real-time "forging" of the medium and high temperature cladding layer,so that the cladding layer changes from "as-cast" to "forged" State” transformation,eliminating defects such as pores,slag inclusions,and cracks in the cladding layer.This article takes H13 die steel as the research object and uses laser shock forging composite additive manufacturing technology to prepare specimens.By examining the crosssectional morphology,metallographic structure,phase,hardness and residual stress of the specimen,compare laser shock forging On the influence of the structure and performance of the cladding layer,the feasibility of laser shock forging composite additive manufacturing technology in the mold repair industry is studied.The main research work and content of this paper are as follows:With the help of ANSYS finite element simulation software,the temperature field changes of the cladding layer during the laser cladding process are simulated.Select the forging characteristics of the H13 die steel,the forging temperature range,and determine the forging laser spot diameter and the movement path of the forging laser according to the forging temperature range of the material and the cladding temperature field simulation results,through the laser spot size and the forging laser movement The speed calculates the forging times of laser impact forging at the same position under different pulse frequencies.Group to study the influence of different laser process parameters on the quality of the cladding layer.The experimental results show that when the defocus amount is,the height of the cladding layer increases with the increase of the defocus amount;when the defocus amount is,the height of the cladding layer decreases with the increase of the defocus amount.When the defocus is around-3.5mm,the photopowder coupling is the most ideal,and the cladding layer height is the largest;when the laser power is between 1000 W and 2000 W,the width and height of the cladding layer increase with the increase of power.The increasing speed is faster between 1000 W and 1800 W,and the increasing speed is slower between 1800 W and 2000W;when the scanning speed is between 2mm/s and 4.5mm/s,the height and width of the cladding layer decrease at a faster rate,4.5 mm/s?6.5mm/s,the decreasing rate of height and width slows down and gradually stabilizes.Based on the simulation results and the research results of the process parameters,the laser shock forging experiment program was designed,and the double laser forging composite additive H13 die steel experiment was carried out.X-ray stress tester,optical microscope(OM),Vickers hardness tester,X-ray diffractometer and other instruments were used to test and analyze the specimens,and compare the effects of laser shock forging under different process parameters.The experimental results show that laser shock forging can significantly improve the internal pores of laser cladding,and the main influencing factor of the number of internal pores in the cladding layer is the pulse laser energy.The increase in the pulse laser energy and frequency can be reduced The size of the pores in the cladding layer;the crystal grain size range of laser cladding specimens is 15-45 um,and the grain size range of dual laser forging composite additive specimens is 5-25 um.Laser shock forging can make The grains of the cladding layer are refined,and the grain structure distribution is more dense,and with the increase of forging frequency,the degree of grain refinement is more uniform;compared with the cladding layer manufactured by double laser forging composite additive material,Under 3J pulsed laser energy,the hardness of 1Hz,2Hz and 5Hz laser shock forging specimens increased by 5.57%,10.22% and 14.80%;under 4J pulsed laser energy,1Hz,2Hz and 5Hz laser shock forging The hardness of the specimens increased by 8.86%,12.38% and 17.43%in turn;under 5J pulsed laser energy,the hardness of the specimens forged by laser shock forging at 1Hz,2Hz and 5Hz increased by 11.62%,16.67% and 20.50%;laser Impact forging can well eliminate the residual tensile stress generated in the laser cladding process,and with the increase of laser energy and pulse frequency,laser impact forging can introduce residual compressive stress to the cladding layer and increase the service life of parts. |
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