Abstract <p>We developed an efficient computational model of thermal processes during friction stir welding (FSW) of heat-resistant alloys using a superhard tool. The model includes only the functional element and the welded components (plates), with appropriate boundary conditions applied to their surfaces. We selected these conditions based on computational experiments using a full model, which comprised the functional element, its tooling, the welded components, and a support plate. The choice of boundary conditions for the efficient model is justified by the contact surfaces of its elements with other FSW equipment and by the distribution of heat flux on the welded components directed toward the support plate. Neglecting heat flux distribution in simplified models introduces significant errors in calculating the temperature field within the welded components. Using the efficient model shortens computational time by a factor of 2 to 2.5 compared with the full model. Numerical experiments identify the FSW process parameters that ensure the thermal stability of the cyborite tool during welding, creating a reliable basis for process optimization.</p>