Thermomechanical and microstructural simulation of rotary friction welding process of Inconel718 alloy using the finite element method

Rotary friction welding is one of the most important techniques for joining different parts in advanced industries. Measuring the history of thermomechanical and microstructural parameters can be challenging and costly. To address these challenges, the finite element method was used to simulate thermomechanical and microstructural aspects of the welding of identical superalloy Inconel718 tubes. Therefore, in this research, thermomechanical and microstructural simulations were developed to calculate essential mechanical and metallurgical parameters such as temperature, strain, strain rate, volume fraction of dynamic recrystallization, and grain size distribution. Some of these parameters were then used to be verified with experimental test results. In the microstructural simulation, the Johnson-Avrami model was applied to convert thermomechanical parameters to metallurgical factors by using a FORTRAN subroutine. By employing the dynamic recrystallization kinetics model, the thickness of the recrystallization zone in the wall thickness was calculated to be 480 and 850 micrometers at the center and edge of the tube wall, respectively. These values were reported in the experimental measurements as 500 and 800 micrometers, respectively. Additionally, the grain size change from the center to the edge of the wall thickness, close to the weld interface, were predicted from 2.07 to 2.15 micrometers by simulations, which was comparable with the experimental measurements of 1.9 to 2.2 micrometers. Also, different types of curves were represented to investigate the correlation between thermomechanical and microstructural parameters. Predictable results were concluded from microstructure evolutions with changes by thermomechanical results.