Microstructure evolution and mechanical properties of friction welded IN713LC and AISI 4140

Abstract

The microstructure and mechanical behavior of rotary friction-welded IN713LC nickel-base superalloy with AISI 4140 steel have been investigated. The microstructure of IN713LC changed from a columnar dendritic structure to equiaxed grains due to dynamic recrystallization with considerable change in in-grain misorientation, morphology, and volume fraction of gamma prime (γ′) precipitates. The observations indicate a counteracting effect of heat input and degree of deformation which resulted in achieving minimum grain size at an intermediate friction pressure. Phase transformation was observed in the weld interface/thermomechanically affected zone region of AISI 4140 steel. These changes in microstructure contribute to the variation in the microhardness across the weld joint. Furthermore, a maximum weld joint tensile strength of 922 MPa was observed at an intermediate friction pressure of 110 MPa.