METHOD FOR RESTORATION AND HARDENING OF STEEL WORKING BLADES OF WET STEAM STAGES OF STEAM TURBINE Russian patent published in 2014 - IPC B23P6/00 B23H9/10 B23K9/04 

FIELD: machine building.

SUBSTANCE: invention can be used in condensing and cogeneration turbines at the repair of working blades (WB) of wet steam stages having part-through defects on the blade airfoil surface on the side of the leading and trailing edges and being subject to erosion destruction or other operational damages. The method involves removal of a protection cover (if any) from each damaged blade, preparation for reconstructive build-up welding by mechanical partial removal of metal in the damaged surface areas, application of metal ductile alloy onto the prepared surface of the blade airfoil on the side of its leading edge by argon-arc build-up pulse welding, mechanical removal of excessive metal resulting from build-up welding, and creation of a protective hardening layer on the blade airfoil surface on the side of the leading and trailing edges along with removal of excessive metal, after all mentioned operations are performed the dimensions of the repaired blade profile shall be put in line with the standardised ones. The said argon-arc build-up welding is carried out by nickel-based metal ductile alloy with further hardening of the build-up layer by surface plastic deformation, afterwards the blade is thermally treated in its built-up part to obtain high-tempered martensite structure, the protection hardening layer is formed by erosion resistant alloy on the blade airfoil surface on its leading edge side over the build-up part by electrospark doping, and on its trailing edge - over the bare metal with further hardening of the said layer by surface plastic deformation.

EFFECT: invention allows for the reduction of inhomogenity in structure-and-phase composition of the repaired WB material, decrease of tensile residual stresses, improve fracture strength, endurance limit, corrosion and erosion resistance of repaired WB metal.

4 cl, 17 dwg