Reserch On The Geometrical Feature And The Molten Pool’s Surface Tension Of Laser Cladding Layer

As a newly emerged process technology, laser cladding technology is widely appliedin the fields such as remanufacture and rapid prototyping due to its excellent advantage.The technological process of laser cladding is based on single-track cladding and the lasercladding is formed by overlapped multi-track or layered deposition. The geometrical formof single-track cladding has direct influence on the dimensional accuracy, surface rough-ness, density and mechanical property of the shaped parts. Therefore, to optimize processparameters and guide the implementation of the technological process, it is of great signi-ficance to study the macroscopic geometric morphology of single-track cladding layer andits formation mechanism.The present paper adopts the alloy powder Ni60as cladding material, and steel45asthe substrate material. The single-track laser cladding experiment is carried out with thepowder pre-setted and different controllable groups of technological parameter, includingthe laser power, scanning rate and powder thickness, are selected. Besides, the macro pro-file of cladding track and cross-section of the cladding layer are observed and the geome-tric parameters are measured.Though the observation of cross-sectional morphology of single cladding layer underdifferent technological parameters, the influence of technological parameters on the mor-phology is analyzed. Based on the morphology characteristics, cladding layer obtained bypresetting method can be classified as non-balling type, sub-balling type, balling type andcracked balling type. The formation mechanism of these types is analyzed according to theinterfacial tension and the formation-evolution process of the molten pool. Basic condi-tions for the balling effect of the cladding layer are proposed, whose accuracy is verifiedby the transient temperature field FEM analysis.The stability of the molten pool is analyzed on the base of the Plateau Rayleigh sta-bility theory. Besides, molten pool stability map is plotted according to necessary and suf-ficient condition of laser cladding molten pool stability. The stability of molten pool canbe determined by molten pool stability model, in which the cross-sectional perimeter ofthe cladding layer obtained by different groups of technological parameters can be ob- tained though measurement and the length of molten pool with the corresponding tech-nological parameters can be obtained by simulation. The comparison of the calculativeresults and the real morphology of cladding track proves that the molten pool stability mapcan accurately reflect the stability of molten pool.Through the analysis of flow mechanism of molten pool and the pressure distributionof free surface, the balance equation of molten pool free surface can be established. Thebalance equation can be simplified according to the characteristic of molten pool and theanalytical model of the molten pool surface tension can be deduced. Surface tension varia-tion of molten pool of different morphology can be used to analyze the correspondingmolten pool flow characteristic.