Rotary Friction Welding of Cast Nickel Base Superalloy with Martensitic Stainless Steel for Aero Engine Application

In the present investigation, rotary friction weld joints were prepared between cast Nickel base super alloy & Martensitic stainless steel which is used for disk and shaft assembly of aero engine respectively. The joints were obtained by rotary friction welding process (RFW), which combines the heat generated from friction between two surfaces and plastic deformation. Test Samples were prepared with different welding process parameters. These test samples were subjected to tensile tests, Vickers micro hardness, metallographic tests and energy dispersive spectrometry (EDS) analysis in scanning electron Microscope after clearance by radiography & fluorescence Penetrant inspection. The friction weld joints revealed radial plastic flow, axial plastic flow, thermo mechanically affected zone in the weld microstructure. EDS analysis at the interface of the junction showed that inter diffusion occurs between the main chemical components of the materials involved. At low friction force & friction time, proper fusion of the two materials was not observed, while micro cracks were observed at the joint when friction force & friction time are increased. An optimum combination of the two, revealed weld joint with proper fusion and no micro crack. These weld joints were evaluated for their mechanical properties by using conventional tensile tests at room temperature and recorded the maximum fracture strength of 1009 MPa. The strength of the joints varied with increasing friction time and the use of different pressure values. Finally, the results were concluded that most of the failure has been observed in the steel side thermo mechanical affected zone (TMAZ). The aim of this research works to emphasis the dissimilar weld joint characteristics for aerospace and defence application. The optimized weld parameter was used to realize the rotor & disk assembly for the aero engine application. The established welding parameters are friction force of 2 ton, upset force 3 Ton, friction time 3.42 s, rotational speed 1700 rpm.