High chromium coating by laser deposition of in 690 for repairing nuclear power plant components

Abstract

Early nuclear power plant components were normally made with Stainless Steel AISI 316L due to its good anticorrosion property before they are replaced by Inconel 600 or Inconel 690 alloys in recent decades. After long time running, these 316L nuclear components are facing severe intergranular stress corrosion under rigorous radiation conditions. To rejuvenate the as-eroded 316L components is vital for long-term sustainable and safe operation of the nuclear power plants. It is approved that the resistance to intergranular stress corrosion cracking and intergranular attack is significantly dependent on the Cr content in the material. SS316L contains only about 17% Cr while In 690 contains about 30%. Laser deposition of In 690 onto 316L to furbish its corrosion-resistant quality is considered as a practical and cost-effective method. The key issue is how to achieve a coating with enough high chromium content by laser deposition of Inconel 690 onto 316L substrate.This paper focuses on investigation on main factors influencing the Cr content in the coating including the dilution rate, laser types, beam energy distribution and laser processing parameters. Results demonstrate that Nd: YAG laser induces high dilution rate to decrease Cr content much more easily than CO2 laser. A rectangular beam is favorable of low dilution while keeping a high deposition rate than a Gaussian beam. Optimized conditions and processing parameters are necessary to guarantee a high Cr content coating up to 27%, which meets the requirements for practical repairing applications. The coatings with higher Cr content show better anticorrosive property.Early nuclear power plant components were normally made with Stainless Steel AISI 316L due to its good anticorrosion property before they are replaced by Inconel 600 or Inconel 690 alloys in recent decades. After long time running, these 316L nuclear components are facing severe intergranular stress corrosion under rigorous radiation conditions. To rejuvenate the as-eroded 316L components is vital for long-term sustainable and safe operation of the nuclear power plants. It is approved that the resistance to intergranular stress corrosion cracking and intergranular attack is significantly dependent on the Cr content in the material. SS316L contains only about 17% Cr while In 690 contains about 30%. Laser deposition of In 690 onto 316L to furbish its corrosion-resistant quality is considered as a practical and cost-effective method. The key issue is how to achieve a coating with enough high chromium content by laser deposition of Inconel 690 onto 316L substrate.This paper focuses on investigation on main fa...