| Stainless steel-nickel base alloy bimetal structure can make the forming parts have the excellent mechanical properties of two materials,but also can save a lot of nickel base alloy resources,reduce the waste of precious metals.It has wide application value in nuclear power,pressure vessel,aerospace,ship vehicle,national defense,military and petrochemical fields.However,there is a great difference in thermal conductivity between stainless steel and nickel-based alloy,which leads to defects such as solidification cracks,brittle intermetallic compounds and pores.Cold metal transition technology(CMT)has the advantage of low welding heat input and can effectively reduce residual stress and deformation of the sediment layer.Using CMT arc additive manufacturing technology to prepare stainless steel-nickel base alloy bimetal structure has great practical significance.In this paper,arc additive manufacturing of 316 L stainless steel and Inconel625nickel-base alloy bimetal structure is studied based on cold metal transition welding arc additive manufacturing equipment.The CMT arc additive manufacturing system was established,and the process parameters of single metal single channel single layer forming were tested to obtain the appropriate welding parameters range of stainless steel and nickel base alloy.The influence of welding parameters on the width and residual height of the weld pass is revealed by analyzing the single metal single pass and single layer test of the two materials,and the optimum technological range of the weld pass forming is determined.And expand the single channel forming database to make a more accurate description of single metal single channel single layer forming.On the basis of single metal single pass forming,the forming process of single multipass welding is studied and the reciprocating stacking path of single multipass welding is determined.Aiming at the width matching problem in the process of stainless steel-nickel base alloy bimetal single channel monolayer forming,the matching test was designed to form bimetal single channel multilayer structure forming specimen with matching width.The "necking" phenomenon in stainless steel-nickel base alloy bimetal structure forming process was optimized,and the metal utilization rate of forming parts was greatly improved.Based on the above research,different bimetal single-channel multilayer forming specimens were deposited.Stainless steel/nickel base alloy was studied the microstructure and mechanical properties of double metal structure,found that the stainless steel,nickel base alloy double metal structure forming good,does not appear crack defects,such as crystal organization mainly for cellular crystal and columnar crystal,the hardness testing experiment,nickel base alloy side than stainless steel side hardness value is high,in the hardness of bimetal combining screen not happen suddenly drops;Results in tensile testing contrast,double metal structure of the tensile strength of the specimens of 349-443 mpa,and the tensile strength of the single metal nickel base alloy approximation,double metal structure fracture location of the specimens in 316 l stainless steel side,fracture mode is ductile fracture,and different welding heat input of double metal pieces of the tensile strength,elongation is inversely proportional to the size of the welding heat input.The experimental results show that the forming quality of stainless steel-nickel base alloy bimetal structure is good,no cracks and other defects,good mechanical properties,in line with arc additive manufacturing forming requirements,verified the rationality of stainless steel-nickel base alloy bimetal structure forming parameters. |
