We studied the effectiveness of application of high-frequency mechanical peening to improve fatigue resistance characteristics of tee welded joints in metal structures which are operated in a sea climate. Corrosion damage characteristic for such structures after long-term service was produced by soaking the welded joints in KST-1 salt spray chamber for 1200 h. Metallographic studies were conducted of weld zone and HAZ of welded joints in the initial (unstrengthened) state and in the state of strengthening by the HFMP technology after the impact of corrosive environment. It was established that strengthening by this technology does not improve the joint resistance to the impact of neutral salt spray. Fatigue testing of welded joints were performed in the initial and strengthened state after the impact of neutral salt spay. It was found that strengthening tee welded joints by HFMP before the corrosive impact allows increasing their fatigue strength at 2•10 6 cycles by 48 % and increasing cyclic fatigue life by 2-5 times. Compactness, mobility and low cost of equipment for high-frequency mechanical peening (HFMP) allows strengthening parts of machines and metal structures in any spatial position in the field, in particular under the water [11]. Works [12][13][14][15] give the results of experimental studies of the effectiveness of application of HFMP technology, known in foreign publications as «ultrasonic shock treatment», to improve corrosion resistance and characteristics of corrosion fatigue resistance of welded joints. In these studies assessment of corrosion resistance, corrosion rate and corrosion fatigue of welded joints was performed in NaCl solutions.Analysis of polarization fatigue curves showed that strengthening by HFMP technology increases the corrosion potential and lowers the corrosion rate of peening zone (line of weld metal transition to HAZ). Here, cyclic fatigue life of butt welded joints of pipes rises 2 times, and that of tee joints -up to 6 times. It should be noted that the above data of accelerated corrosion testing do not give an idea about lowering of service properties of HFMP-treated welded joints as the strengthened metal layer is destroyed.Influence of partial corrosion loss of HFMP-strengthened metal layer on residual stress fields and cyclic fatigue life of welded joints is considered in [16,17]. In [16] it is shown that corrosion damage of welded joints of low-alloyed shipbuilding steel equivalent to 7.5 years of operation leads to reduction of the thickness of surface layer of metal with induced residual compressive stresses approximately from 1.5 to 1.0 mm, and lowering of their maximum level. The authors came to the conclusion about the rationality of welded joint treatment by HFMP, as compressive residual stresses are induced in the peening zone instead of tensile residual stresses, and they are preserved even at partial loss of the strengthened layer. In [17] metallographic studies showed that soaking of welded joints of weather-resistant steel in moisture chamber G4 at elevat...
