Loss of tightness of the sealing surfaces of pipe fittings is one of the most common causes of pipeline failures. The most loaded valve assembly is the wedge gate, which operates under harsh conditions of tribological wedge–saddle contact with significant pressure drops and intense flow dynamics. When the wedge is planted and moving, local stresses on the sealing chamfers can exceed the yield strength of the material, causing adhesive setting, scuffing, and intense plastic shear of the surface layer. The additional effect of hydrodynamic factors of the working environment – cavitation and waterjet erosion – significantly accelerates the destruction of the microstructure of structural steels and surfacing materials. Timely prevention of node failure requires a comprehensive analysis of the processes in the contact area, combining numerical modeling with metallographic studies. Joint numerical modeling makes it possible to determine with high accuracy the location of the zones of maximum equivalent stresses according to Mises, taking into account the physical and mechanical properties of the working medium. A comparison of the calculated stress concentration zones with metallography data and microhardness profiles reveals the physical nature of corrosion-mechanical and erosive wear. Thus, pitting corrosion and cavitation destruction prevail in the aquatic environment; high-speed gas flows provoke intense erosive wear; and viscous petroleum products change the distribution of the lubricating layer and contact pressure. The formation of wear-resistant surface layers through corrosion resistant surfacing and surface plastic deformation reduces the destruction of the microstructure and prevents the nucleation of microcracks. A reasonable choice of the geometry of the contact pair and the technological parameters of hardening ensures that the required sealing class of the gate according to GOST 9544-2015 is maintained throughout the entire standard service life of the valve. Keywords: wedge gate, tribo-tension, contact interaction, stress-strain state, microstructure, microhardness, working medium, computer modeling.