Study on Laser-TIG Dissimilar Welds of Cemented Carbide and Invar Alloys Welded with CO2 Laser

Invar alloy has lower thermal expansion and is widely used. However, its intensity is too low to meet the requirement of industry. In order to improve its high-temperature strength, WC-Co cemented carbide was welded to invar alloy using high energy Laser-TIG (Tungsten Inert Gas) hybrid welding. WC migration phenomenon was discovered in welding process and its corresponding mechanism was discussed. Microstructure at different interface was discussed and the hardness profile was measured. The results showed: (1) Butt joint of WC-Co/ invar alloy manifested well penetration without any filler materials; (2) WC migration near WC-Co/ weld interface was owed to synthesis action including stirring effects of welds, intrinsic Stress, high pressure of molten materials and ionized shielding gas, interface reaction and surface tension.