A new method for restoring worn surfaces of steel parts of pumping equipment, nuclear power plants

Abstract

The paper proposes a new method of restoring worn surfaces of steel parts of pumping equipment used at nuclear power plants and subjected to radiation irradiation. The method belongs to the field of electrophysical and electrochemical treatment, in particular to electrospark alloying (ESA), and is applicable to repair parts of machines of nuclear power plants. The EBS method has a number of specific features: the anode material (alloyed material) can form a coating layer on the cathode surface (alloyed surface) that is extremely strongly bonded to the surface; the alloying can be performed in strictly specified places without protecting the rest of the part surface; the ESA technology for metal surfaces is very simple, and the necessary equipment is compact and transportable. The method includes coating of the worn surface of the part by electroplating with the same metal electrode - an instrument made of material (steel 12X18H10T or nickel) without special additives of cobalt and other elements that form long-lived isotopes in the active working environment. The electrodeposition is carried out in two stages. Before the first stage of coating with metallic electrode-tool a layer of coating with graphite electrode-tool with discharge energy Wp = 0.02 J and capacity 0.3 cm2/min is applied to the worn-out steel surface by ESA method, Then the first stage of coating layer application by ESA method by the metal electrode/tool at discharge energy 0.20-0.55 J and productivity 1.6-2.5 cm2/min ensuring surface thickness 0.09-0.16 mm and its continuity 100% , after that the surface obtained is subjected to the second stage of coating layer application by ESA method by the same metal electrode/tool with discharge energy 0.55-0.90 J and productivity 2.5-3.4 cm2/min.