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Product Code: ICAL07_2001

High Chromium Coating by Laser Deposition of IN 690 for Repairing Nuclear Power Plant Components
Authors:
Minlin Zhong, Tsinghua University; Beijing Peoples Republic of China
Qian Hao, Tsinghua Univ.; Beijing Peoples Republic of China
Renjie Zhu, Tsinghua University; Beijing Peoples Republic of China
Wenjin Liu, Tsinghua University; Beijing Peoples Republic of China
Hongjun Zhang, Tsinghua University; Beijing Peoples Republic of China
Presented at ICALEO 2007

Early nuclear power plant components were normally made with Stainless Steel ANSI 316L due to its good anticorrosion property before they are replaced by In 600 or In 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 (IGSCC) and intergranular attack (IGA) is significantly dependent on the Cr content in the material. 316L contains only 17% Cr while In 690 contains about 30%. Laser deposition of Inco 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 In 690 onto 316L substrate. This paper focuses on investigation on main factors influencing the Cr content in the coating including different lasers, the dilution rate, the behavior of Cr element in the melt pool and the beam energy distribution. Results demonstrate that Nd: YAG laser much more easily induces high dilution rate to decrease Cr content than CO2 laser. A rectangular beam is favorable of low dilution while keeping a high deposition rate than a Gaussian beam. The understanding of the behavior of Cr in the melt pool driven by strong convection is helpful for the Cr control. Optimized conditions and processing parameters are necessary to guarantee a high Cr coating up to 27%, which meets the requirements for practical repairing applications.

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