Microstructure and mechanical property of linear friction welded nickel-based superalloy joint

Nickel-based superalloy joints were welded by linear friction welding under different processing conditions. The influences of process parameters on microstructure and mechanical properties of joints were investigated. The results indicate that sound microstructure such as fine recrystallized grains in the weld zone could be obtained under certain conditions. Microstructural examination shows that grains in the thermomechanically affected zone present no obvious deformation. Moreover, the segregation of some impurity elements along grain boundaries and the reversion of γ″ and γ' caused by high interface temperature during welding lead to the reduction of joint mechanical property. The microhardness and tensile strength of joints are lower than those of the parent metal. In addition, a weak layer including residues of oxides and carbides on the extremities of the joint is formed unexpectedly, which is detrimental to joint integrity.