Abstract <p>The processes of inertia and linear friction welding of heat-resistant nickel alloys VZh-175, EP-742, and EP-741 are discussed. The programs developed for analyzing the characteristics for linear and inertia friction welding are analyzed. The developed finite-difference models of the temperature field are also described, the main features of which are the movement of the friction boundary, which simulates the process of upsetting. The analysis of the kinematic, force, energy, and temperature characteristics of linear and rotary friction welding cycles is carried out. Comparison of linear and rotary welding cycles by 14 characteristics showed that the most informative in terms of data transfer are the upsetting rate and the upset value, the temperature at the joint, the specific thermal power, work on upsetting the unit volume, and the coefficient of friction.</p>