Research On Characterization And Control Of Residual Stress In Laser Cladding Remanufacturing

Residual stress is one of the most urgent problems to be solved in large-scale commercial applications of laser cladding additive manufacturing and remanufacturing.The intense temperature field evolution during the laser cladding process will inevitably be accompanied by stress and strain evolution,resulting in high levels of residual stress in the part.The residual stress will affect the serviceability and safety of the part,and even cause the part to be scrapped due to cracking and deformation during the manufacturing process.However,most of the existing methods for measuring residual stress are limited to surface residual stress.Under actual working conditions,only studying the distribution of surface residual stress has limited guiding effect on actual production.Therefore,it is of great scientific and practical significance to study the evolution law and mechanism of stress along the depth direction during laser cladding to better achieve the regulation and control of the residual stress level and distribution.In this paper,the evolution of microstructure,hardness and residual stress along the cladding depth during the laser cladding remanufacturing process is described.The influence law and mechanism of the laser energy density on the evolution of the stress field are discussed.The adjustment of the residual stress level and the adjustment of the heat input are discussed Method of distribution.First,using laser cladding technology based on synchronous powder feeding,two groups of Fe-based cladding samples with the same single parameter thickness less than 1 mm,dense structure and high hardness were prepared on the surface of Q345 steel.Using the method of color flaw detection,the crack statistics of the surface of the cladding sample were analyzed.The correlation between the energy density of the laser cladding and the crack sensitivity was established.The main factors affecting the macro morphology of the laser cladding surface were discussed.The best laser cladding process parameters under specific materials.Secondly,using scanning electron microscopy(SEM)and line scanning(EDS)techniques,the organization evolution of the cladding layer and the heat affected zone under different laser energy densities was studied,and the influence from cladding layer to heat under different laser energy densities was analyzed.The element distribution law of the zone summarizes the influence of the laser energy density on the formability of the cladding layer,the heat-affected zone and the microstructure and hardness of the cladding layer,revealing the strengthening mechanism of the Q345 steel cladding layer Well,the cladding layer with a width of about 0.7mm in the heat-affected zone.The hardness of the cladding layer is 420 ~ 592 HV,which is mainly caused by phase transformation strengthening and solid solution strengthening,and increases with the increase of laser energy density.Then,the stripping method based on electrochemical corrosion and X-ray diffraction was used to measure the residual stress from the surface of the cladding layer to the heat-affected zone on another group of samples with the same parameters,and the measured values were based on the relevant knowledge of material mechanics.Amended.Characterized the distribution of residual stress along the depth direction,discussed the effect of laser energy density on the residual stress of laser cladding,revealed the internal relationship between residual stress and macroscopic crack distribution,and obtained the best energy to reduce the level of residual stress Density interval.Finally,based on the effect of the stacking strategy on the residual stress of laser cladding,the orthogonal experiment method was used to change the cladding path in the laser cladding process.The effect of laser energy density on the crack distribution on the cladding surface under different cladding paths was discussed.According to the law,the effect mechanism of laser energy density on the residual stress distribution of the laser cladding sample cladding layer and heat affected zone under different cladding paths is obtained by the stripping method,and the laser cladding energy density-residual stress-macro crack three is established.The relationship between the two.The paper has 38 pictures,7 tables,and 81 references.