Process Numerical Simulation Of Laser Cladding On The Inclined Substrate

As one of the most promising remanufacturing technologies,laser cladding has been mainly studied based on the substrate level status,while the actual repair process often involves complex surfaces.Therefore,inclined substrate repair is the basis for studying complex surface repair.In this thesis,laser cladding with 316 L powder was studied,and the morphology of single and multi-layer overlaps on the inclined substrate was investigated using a combination of simulation and experimentation.The main contents of this thesis are as follows:A central composite design was used with Design Expert software to establish a second-order regression model between process parameters and the geometric morphology of the inclined cladding layer,and the residual distribution and reliability of the model were analyzed.The effects of four process parameters(laser power,powder feeding rate,scanning speed,and inclination angle)on the geometric morphology features(height,width,and peak point shifting)of the cladding layer were explored through process experiments.The heat and mass transfer process of the molten pool during single-layer cladding was studied.The heat and mass transfer during single-layer laser cladding at different positions and times,under different parameters and along the transverse section in the direction of laser movement were analyzed.The results showed that gravity under inclined conditions was the main reason for the peak point shifting,and the velocity field in the gravity direction was larger.The larger the inclination angle,the greater the influence on the velocity field,and the maximum velocity occurred at the end of the gravity direction,resulting in a more obvious inclined water droplet-like morphology of the cladding layer.Finally,the solidification process of the molten pool was analyzed,and the results showed that the height of the cladding layer did not have a significant effect on the tissue morphology of different positions from high to low,mainly affecting the size of the grains.The flow of the molten pool and the final cladding layer morphology of laser cladding on inclined substrates with different paths were analyzed using a simulation model.The results showed that before the inclination angle reached 90°,there was a certain regularity in the variation of the cladding layer morphology.When the inclination angle was greater than 90°,splashing and dropping occurred in several scanning paths,and the cladding layer morphology was extremely unstable.It was not suitable to use coaxial powder feeding when the inclination angle was too large.The overlapped cladding layers scanned in the positive direction of x and negative direction of y under inclined conditions were the most stable.To further improve the quality of inclined substrate laser cladding,laser remelting experiments and numerical simulations were carried out on the cladding layer surface.The experimental and simulation results showed that remelting could significantly reduce surface roughness,microstructure grain refinement,and improve hardness and wear resistance.This thesis includes 68 figures,12 tables,and 87 references.