Microstructure And Properties Of 316L-IN625 Functionally Gradient Material Via Laser Metal Deposition

The pursuit of high performance for composite components of dissimilar materials has never stopped in the fields of aerospace,automobile and other fields.However,the physical properties of dissimilar materials are quite different.Under severe service conditions,composite components produced by conventional manufacturing methods cannot meet the multiple requirements of high strength,high ductility,and corrosion resistance.As a kind of additive manufacturing,laser metal deposition has become an effective way to solve this problem by using its flexible manufacturing function to form functionally gradient materials.Considering the high strength of IN625 and the good ductility of 316L,this paper uses laser metal deposition to form 316L-IN625 functionally gradient material,and conducts high temperature annealing treatment to study its microstructure,mechanical properties,and corrosion properties.The specific content is as follows:1.Research on the geometric characteristics of the surface and cross section of 316L and 316L-IN625 single-pass deposition cladding.By changing the process parameters,the internal relationship between the process parameters and the surface and cross-sectional geometric characteristics of a single-pass deposited coating is studied.The results show that the depth of the surface valley value depends on the height of the deposited coating,and The peak height of the surface depends on the powder supply rate.The increase in the height of the deposited coating and the shielding of the laser beam by the powder flow causes the absolute value of the melting penetration depth is reduced.2.Research on the correlation between the microstructure and properties of 316L-IN625 functionally gradient material.The solidification microstructure under different cooling conditions is obtained by changing the scanning speed,and the typical solidification microstructure and its corresponding mechanical properties and corrosion properties are studied.The results show that the crystal grains along the deposition build direction are:celluar dendrites,columnar crystals,coarse dendrites,and nearly equiaxed crystals.The 0.2%yield strength of the316L-IN625 gradient sample is up to 289 MPa.The corrosion products in the 316L area are composed of Fe_2.6Cr_0.4O₄,?-Fe₂O₃and Ni Fe₂O₄.Due to the dissolution of the surface passivation film in 40%316L area,30%316L area,and IN625 area,the mixed Cr(III/VI)oxide located in the inner layer of the passivation film is exposed as the final corrosion products.3.Research on the correlation between the microstructure and properties of the 316L-IN625 functionally gradient material after high temperature annealing.The homogenization of the rapid solidification structure is achieved through high temperature annealing.The improvement of the mechanical properties of the annealing microstructure and the difference in the corrosion performance of the gradient interface before and after annealing are studied.The results show that in the annealed microstructure of the 316L-IN625 gradient sample,metal oxides rich in Cr and Mn are produced in the 316L region,and mixed precipitates rich in Nb,Al,and Mo are produced in the gradient region.When the annealing temperature is 1250?,the tensile strength and ductility of 316L-IN625 gradient sample is improved.Compared to before annealing,the interface 70%316L-40%316L has a stable passivation zone after annealing at 1250?.The corrosion products are composed of?-Fe OOH,Fe₃O₄and Cr O₃.?-Fe OOH achieves stable passivation by reducing the corrosion reaction rate.