Research On Laser Welding Of Inconel601 Nickel Based Superalloy

Because of the advantage of excellent mechanical properties and corrosion resistance, the Inconel601 nickel based superalloy has been widely applied in many fields, such as ferrous metallurgy, electric and energy industry, petrochemical industry and aerospace. In order to improve the material utilization and save energy, the Inconel601 structures are gradually developing from forging to welding, but there are a lot of welding problems when using traditional welding methods. Laser welding has become the first alternative for nickel based superalloy due to its advantage of deep penetration and small heat input. In order to meet the practical application, the laser welding procedure, properties of welded joint, solution treatment after welding and the welding quality have been investigated in this paper.At first, the laser welding procedure and joint properties have been researched. The boundary curve of full penetration laser welding of 3mm thick solution-annealed Inconel601 sheet was determined based on experiments. The microstructure and mechanical properties of the welded joint with different welding heat input was discussed, and a group of weld joints with optimal mechanical properties have been selected for corrosion test. Result shows, the welded joints have good mechanical properties when the welding heat input is between 333J/mm～400J/mm, but the laser welded joints of Inconel601 superalloy has a tendency of intergranular corrosion because of the"Cr depleted zone"in the weld metal, and the oxidation resistance of welded joints was slightly lower than base metal.Secondly, solution treatment after weld of Inconel601 superalloy was studied. As the solution temperature increased, the tensile strength of laser welded joints decreased slightly, and the elongation shows a tendency of first increased and then decreased. Recrystallization phenomena occurred in the weld metal after solution heat treatment, and the welded joint has homogeneous, equiaxed grains, while the intergranular corrosion tendency of welded joints was disappeared, but excessive high solution temperature would result in grain growth and the emergence of intergranular corrosion. In addition, the oxidation resistance of welded joints improved with the increase of the solution temperature. Finally, defect assessment methods of laser welding based on acoustic signals have been investigated. A multi-channel acoustic acquisition system for laser welding was been constructed. The easily captured acoustic signals which are not sensitive to the sensor's position and orientation were used to distinguish the welding defects. The FastICA algorithm was used to extract useful welding acoustic signal from acquisition signals, and realized the laser welding perforation defect recognition based on acoustic signal through the time-frequency analysis method.