Abstract
Laser beam welding (LBW) has been considered an effective fusion welding method for the dissimilar welding of 304 stainless steel and Ni. However, the principles governing the correlations between the heat input, weld dimension, solidified microstructure and mechanical properties have not been fully studied before. Therefore, LBW experiments with variable heat input were carried out. A transient, three-dimensional model considering liquid metal convection was developed, and solidification parameters such as temperature gradient (G), growth rate (R), and cooling rate (GR) were calculated through thermal analysis to validate the experimental results. Then, microhardness tests were carried out to verify the predications made by the simulation. Energy dispersive spectroscopy (EDS) measurements were performed to study the mass transfer. The results indicate that the joints produced by LBW were nearly defect-free. The heat input per unit length is more effective at characterizing the influence of heat input on weld dimensions. The heat input has a greater influence on the cooling rate (GR) than the morphology parameter (G/R). The results demonstrate that both the solidification characteristics and mechanical property are greatly affected by the thermal behavior in the molten pool.
Highlights
Nickel and nickel-based alloys have excellent corrosion resistance [1], and 304 stainless steel is a Cr-Ni stainless steel with excellent heat resistance and machinability [2]
The results indicate that the joints produced by Laser beam welding (LBW) were nearly defect-free
The results demonstrate that both the solidification characteristics and mechanical property are greatly affected by the thermal behavior in the molten pool
Summary
Nickel and nickel-based alloys have excellent corrosion resistance [1], and 304 stainless steel is a Cr-Ni stainless steel with excellent heat resistance and machinability [2]. Joints of Ni and 304ss are widely used in the fields of petrochemical, steel metallurgy, and aerospace. Laser beam welding (LBW) has attracted increasing attention for the advantages of the high precision, lower heat input, and flexible transmission [3,4]. Both the Ni and 304ss show good welding adaptability to LBW [5]. Due to differences in thermal and mechanical properties such as thermal conductivity, heat capacity, and viscosity, etc., brittle intermetallic compounds are prone to occur, and elements at the grain boundaries are enriched in dissimilar welding [6]. The joint is susceptible to cracks and failures. Simulations on thermal behavior and solidification parameters in the molten pool could be used to qualitatively predict the solidification microstructure and mechanical properties [7]
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