Zhihui Wang

Effect of Temperature on Formation of Borides in TLP Joint of a Kind of Nickel-Base Single Crystal Superalloy

a kind of as-cast nickel-base single crystal superalloy was TLP bonded using Ni-Cr-B amorphous foil at different temperatures. Special attention is paid to the formation of boride in diffusion zone of TLP joints at different conditions. The chemical composition and microstructure of borides were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). At different bonding temperature, M3B2 precipitates appear distinct morphologies. At 1200°C, both blocky and plate-like borides formed owing to the diffusion of boron atoms into base metal and precipitation during the cooling process. At 1230°C or above, due to the diffusion of boron atoms the constitutional liquation of original γ/γ′ eutectics in the base metal occurs and borides formed when the system was cooled to room temperature. The analysis of TEM results reveals that M3B2 has a tetragonal structure and is rich in Mo, W, and Cr elements.