A new current hybrid inertia friction welding for nickel-based superalloy K418–alloy steel 42CrMo dissimilar metals

Abstract

The nickel-based superalloy K418 and alloy steel 42CrMo dissimilar metals friction welding joints lack strength and toughness due to high hardening and poor joining quality at the friction interface. To resolve this issue, a new current inertia friction welding (CIFW) method is carried out by hybrid an external additional electronic current in inertia friction welding (IFW) process. The characteristics of welding formation, the elements’ diffusion, and the mechanical properties of K418–42CrMo dissimilar metal joints are studied by scanning electron microscope, energy dispersive spectrometer, and X-ray diffractometer tools. The experimental results show that hybrid additional electronic current has a significant positive influence on interface characteristics of IFW joints. The required welding time for CIFW to complete a good qualified joint is shortened due to mixture actions of both friction heat and resistance heat. The width of the element diffusion zone increases in CIFW joints, and elements in 42CrMo side diffuse through the K418/42CrMo interface into the K418 side in CIFW joints. The width of the K418/42CrMo bonding interface increases in CIFW joints. The microhardness at the K418/42CrMo bonding interface is decreased in CIFW joints. The mechanical tensile property of CIFW joints is increased obviously. The interface bonding pattern becomes jagged and interlocking perfect formations. These above changes improve the joining quality of K418–42CrMo dissimilar metal friction welding joints. The heat treatment effect and resistance heat effect originated from hybrid external electronic currents are discussed by comparing CIFW with IFW. A new model is proposed to illustrate the interface’s evolution and development mechanism in K418–42CrMo dissimilar metal CIFW.