Microstructure and mechanical properties of GH3535 superalloy joints using keyhole TIG welding

Single-pass keyhole TIG welding (K-TIG) was used to weld 10-mm-thick GH3535 superalloy plates without filler metal and groove preparation. The microstructure and mechanical properties of GH3535 superalloy welded joints were investigated. The results show that columnar crystals symmetrically grow in the fusion zone (FZ) and the contact angle between the symmetric columnar crystals is approximately 115 degrees. A few eutectic phases of M6C- gamma are observed in a partially melted zone (PMZ) of the heat-affected zone (HAZ). The microhardness of HAZ is higher than that of FZ and the base metal (BM). The tensile strength of joints at room temperature, 650 degrees C, and 700 degrees C were 98%, 101%, and 99% of the BM, respectively. The results show that K-TIG welding is suitable for joining middle-thick GH3535 superalloy plates.