Influence Of Heat Treatment On Structures And Properties Of Ni₅₆ Cr₂₂ Mo₁₃ Alloy Weld

Nickel base alloy is an important anti-corrosive metal material, is different from stainless steel, other anti-corrosive metal and nonmetallic material. Not only nickel-alloy have the ability to resistance in various corrosive environment(including chemical and electrochemical corrosion), but also have high-intensity and can melting, casting forming, hot deformation and weldability. it can solve the problem that general stainless steel and metal materials, nonmetal material cannot do it in the engineering. As an important material, Ni₅₆Cr₍22_Mo₁₃ meet a welding problem inevitably, it used to be weld by tungsten pole argon arc welding (TIG). Weld moulding process experienced three important stages, such as heating melting, solidification and solid phase change. Weld have low strength and corrosion resistance because of cast microstructure, and affect the overall performance and long service life of nickel base alloy.This subject adopt TIG and LBW method to weld Ni₅₆Cr₍22_Mo₁₃, research the influence of heat treatment on structures and properties of Ni₅₆Cr₍22_Mo₁₃ weld. So as to optimize heat treatment process, finally comparing different welding method to the weld. Finally investigate microstructure and corrosive morphology, phase and component analysis by the way of metallographic microscope, SEM, XRD and EDS.The results of the study indicate that: metal tissue exhalation a lot of precipitation phase, due to welding process is equivalent to the sensitization processing, weld modal weld microstructure for as-cast organization, dry branches and branch wafer intergranular segregation is serious, composition is uneven. It caused by the welding process of molten pool fast non-equilibrium crystallizing. It can improving the weld's function by solution treatment, it let the phasedissolves in matrix and make alloy composition more uniform. Separation material contains more Mo, it is required to obtain it from based phase, so it cause serious intercrystalline corrosive. It increase Cr, Mo and W in the matrix, so it enhance strength of weld and eliminate some harmful intermetallic.Austenitic grain begin coarsening when the solution temperature is high, solution time is long and cooling speed is slow.Corrosion rate is low after solid solution, it is solid solution state organization after solid solution, reduced the as-cast alloy composition segregation, it explains that the weld corrosion resistance is close to its structure, it is single-phase austenitic organization after water-cooled 1120℃×2h solid solution treated, its hardness is 230HV, corrosion rate is 4.2 mm/a, corrosion potential is -54.81 mV, corrosion current is 2.97μA,so it shows that it has good corrosion resistance.Due to the laser welding of cooling speed is faster than argon arc welding of cooling speed, so heat affected zone is small, laser welding make the weld structure more uniform because of the purification effect and a series of characteristics, so the weld is much more corrosion resistance. So the weld's corrosion potential is -40.15mV, corrosion current is 2.80μA.