Analysis and Control of Cracks in Shroud of Aero-engine High Pressure Turbine Blade after Welding

Some delayed cracks were found at welding heat affected zone after wear-resistant layer was welded on damping shroud surface of high pressure turbine blade. The cause of cracks was analyzed by chemical composition analysis, metallographic microscopy and SEM observation. The results show that the strain concentration in the overheated zone caused by the comprehensive effect of residual welding and grinding stresses and aging microstructure stress resulted in strain aging crack in the grain boundary. By preheating before welding, cooling slowly and annealing immediately after welding, controlling blade grinding feed and other measures, the crack failure rate can be effectively reduced. The cold and thermal cycling test indicated that the cracks were unlikely to turn into closed cracks because the cracks' propagation rate is slow under normal work condition, but the cracks on the edge had a tendency to extend to be closed, affecting the flight safety.