Comparison on corrosion-resistance of Inconel 690 coatings by Nd:YAG laser and CO2 laser deposition for repairing nuclear power plant component

Abstract

Laser deposition is considered as a promising approach for repairing or rejuvenating as-eroded nuclear power plant components after a long period of operation to restore their resistance to intergranular stress corrosion (IGSC) within rigorous radiation environment. The IGSC performance is significantly dependent on the Cr content in the material. Inconel 690 with up to 30%Cr is usually used as deposition powder for this purpose. In our previous research, we had achieved coatings with high chromium content up to 27%Cr by laser deposition of Inconel 690 onto 316L substrate using Nd: YAG laser and CO2 laser and investigated the corrosion-resistance of the as deposited coatings. Research results indicated that normally the coating with high Cr content shows better corrosion resistance than that with lower Cr content. However, we accidentally observed that the coatings deposited by Nd: YAG laser with even lower Cr content demonstrate better corrosion resistance than the coatings by CO2 laser. This is a rather interesting phenomenon. This paper further investigates the phenomenon and studies the reasons, which will be important for potential applications. The paper will focus on deep analysis and comparison on microstructure, phase and composition characteristics of the coatings by these two types of laser with same or different Cr content and clarifying their influence on the corrosion resistance.Laser deposition is considered as a promising approach for repairing or rejuvenating as-eroded nuclear power plant components after a long period of operation to restore their resistance to intergranular stress corrosion (IGSC) within rigorous radiation environment. The IGSC performance is significantly dependent on the Cr content in the material. Inconel 690 with up to 30%Cr is usually used as deposition powder for this purpose. In our previous research, we had achieved coatings with high chromium content up to 27%Cr by laser deposition of Inconel 690 onto 316L substrate using Nd: YAG laser and CO2 laser and investigated the corrosion-resistance of the as deposited coatings. Research results indicated that normally the coating with high Cr content shows better corrosion resistance than that with lower Cr content. However, we accidentally observed that the coatings deposited by Nd: YAG laser with even lower Cr content demonstrate better corrosion resistance than the coatings by CO2 laser. This is a rather...