Search

EP-4739809-A1 - METHOD FOR MANUFACTURING A NUCLEAR REACTOR COMPONENT AND RESULTING NUCLEAR REACTOR COMPONENT

EP4739809A1EP 4739809 A1EP4739809 A1EP 4739809A1EP-4739809-A1

Abstract

The manufacturing method comprises obtaining a strip of nickel-based alloy having a composition, in percentages by weight: trace amounts ≤ C ≤ 0.08%; trace amounts ≤ Mn ≤ 0.35%; trace amounts ≤ Si ≤ 0.35%; trace amounts ≤ P ≤ 0.015%; trace amounts ≤ S ≤ 0.015%; 17.0% ≤ Cr ≤ 21.0%; trace amounts ≤ Co ≤ 1.0%; 2.80% ≤ Mo ≤ 3.30%; 4.75% ≤ Nb + Ta ≤ 5.50%; 0.65% ≤ Ti ≤ 1.15%; 0.20% ≤ Al ≤ 0.80%; trace amounts ≤ Cu ≤ 0.30%; 50.0% ≤ Ni ≤ 55.0%; trace amounts ≤ B ≤ 0.006%; the balance being Fe and impurities resulting from the production, and performing desensitization annealing in a static furnace at an annealing temperature equal to or higher than 900°C and/or equal to or lower than 1050°C for an annealing time equal to or greater than 1 min and/or equal to or less than 180 min.

Inventors

  • ANDRIEU, ERIC
  • CLOUE, JEAN MARC
  • BARDEL, Didier
  • SIMONOT, CLAUDE
  • BADINIER, Guillaume

Assignees

  • FRAMATOME

Dates

Publication Date
20260513
Application Date
20240704

Claims (18)

  1. 1. A method of manufacturing a component of a nuclear reactor, in particular a light water nuclear reactor, the manufacturing method comprising the steps of: obtaining a strip made of a nickel-based alloy of chemical composition, expressed in weight percentages: traces < C < 0.08%; traces < Mn < 0.35%; traces < Si < 0.35%; traces < P < 0.015%; traces < S < 0.015%; 17.0% < Cr < 21.0%; traces < Co < 1.0%; 2.80 < Mo < 3.30%; 4.75% < Nb + Ta < 5.50%; 0.65% < Ti < 1.15%; 0.20% < Al < 0.80%; traces < Cu < 0.30%; 50.0% < Ni < 55.0%; traces < B < 0.006%; the remainder being Fe and impurities resulting from the elaboration; carrying out a desensitization annealing of the strip in a static furnace to obtain an annealed strip, comprising maintaining the strip at an annealing temperature equal to or greater than 900°C, in particular equal to or greater than 920°C, preferably equal to or greater than 940°C and/or equal to or less than 1050°C, in particular equal to or less than 1000°C, preferably equal to or less than 980°C, for an annealing time equal to or greater than 1 min, in particular equal to or greater than 15 min, preferably equal to or greater than 30 min and/or equal to or less than 180 min; and shaping the annealed strip to obtain the component.
  2. 2. A method according to claim 1, wherein, during the desensitization annealing step, the strip is heated from an initial temperature, for example room temperature, to the annealing temperature and then maintained at the annealing temperature for the annealing duration.
  3. 3. Method according to claim 1 or 2, wherein, in the desensitization annealing step, the strip is heated to the annealing temperature with a heating rate of less than 100°C/min, preferably less than 50°C/min, in particular less than 20°C/min and/or the heating rate of the strip is greater than 0.5°C/min, preferably greater than 2°C/min, in particular greater than 4°C/min.
  4. 4. Method according to any one of the preceding claims, comprising, after the desensitization annealing step, a step of active cooling of the annealed strip carried out before the shaping step, preferably at least as long as the temperature of the strip is equal to or greater than a cooling temperature, for example equal to 600°C.
  5. 5. A method according to any preceding claim, wherein the desensitization annealing step is carried out under vacuum or under a protective atmosphere, for example a non-oxidizing atmosphere, in particular a non-oxidizing atmosphere formed of argon and/or hydrogen.
  6. 6. A method according to any preceding claim, wherein the desensitization annealing step is carried out on the strip packaged in the form of a coil.
  7. 7. A method according to any preceding claim, wherein the strip has a thickness equal to or less than 0.70 mm, in particular a thickness equal to or less than 0.60 mm, preferably a thickness equal to or less than 0.30 mm.
  8. 8. Method according to any one of the preceding claims, in which, at the end of the desensitization annealing step, the phase 5 content of the microstructure of the nickel-based alloy is equal to or greater than 0.1%, in particular equal to or greater than 1%, preferably equal to or greater than 3% and/or equal to or less than 17%, in particular equal to or less than 12%, preferably equal to or less than 8%.
  9. 9. A method according to any preceding claim, wherein the shaping step comprises one or more sub-steps of planing, cutting, stamping, bending and/or machining.
  10. 10. A method according to any preceding claim, wherein the step of obtaining the strip comprises one or more of the following steps: obtaining an ingot made from the nickel-based alloy; carrying out a homogenization annealing of the ingot; hot transformation of the ingot to obtain a hot-transformed product; cold transformation of the hot-transformed product to obtain the strip, the cold transformation being carried out in a cold transformation step or a series of cold transformation sub-steps with an intermediate annealing sub-step between each cold transformation sub-step and the next; and/or an intermediate annealing step between the hot transformation step and the cold transformation step.
  11. 11. Method according to claim 10, carried out without annealing between the cold transformation step and the desensitization annealing step.
  12. 12. Method according to any one of the preceding claims, comprising an aging annealing step carried out after the desensitization annealing step, preferably carried out at a temperature equal to or greater than 500°C and/or equal to or less than 800°C and/or for a duration equal to or greater than 1 h and/or equal to or less than 100 h.
  13. 13. The method of claim 12, wherein the aging annealing step is performed after the shaping step and/or during the shaping step.
  14. 14. A method according to claim 12 or claim 13, without annealing the nickel-based alloy between the desensitization annealing step and the aging annealing step.
  15. 15. Method according to any one of the preceding claims, without annealing of the nickel-based alloy after the desensitization annealing step.
  16. 16. A method according to any preceding claim, wherein the component is a nuclear fuel assembly element, in particular an element of a spacer grid of a nuclear fuel assembly, an element of a mixing grid of a nuclear fuel assembly or a spring of a nuclear fuel assembly.
  17. 17. Nickel-based alloy component of a nuclear reactor, in particular a light water reactor, produced according to a manufacturing method according to any one of the preceding claims.
  18. 18. Component according to claim 17, in which, at the end of the desensitization annealing step, the phase 5 content of the microstructure of the nickel-based alloy is equal to or greater than 0.1%, in particular equal to or greater than 1%, preferably equal to or greater than 3% and/or equal to or less than 17%, in particular equal to or less than 12%, preferably equal to or less than 8%.

Description

Method of manufacturing a nuclear reactor component and nuclear reactor component thus obtained The present invention relates to the field of nickel superalloys, and more specifically the nickel-based alloy known as INCONEL® 718 (or NC19FeNb) corresponding to the UNS N07718 standard, which is used, for example, to manufacture components of light water nuclear reactors (or LWR), for example structural components or components of nuclear fuel assemblies intended to be inserted into these light water nuclear reactors. The classical chemical composition of the INCONEL®718 alloy (name which will subsequently be abbreviated to “alloy 718”) is as follows: traces < C < 0.08%; traces < Mn < 0.35%; traces < Si < 0.35%; traces < P < 0.015%; traces < S < 0.015%; - 17.0% < Cr < 21.0%; traces < Co < 1.0%; - 2.80 < Mo < 3.30%; - 4.75% < Nb + Ta < 5.50%; - 0.65% < Ti < 1.15%; - 0.20% < Al < 0.80%; traces < Cu < 0.30%; - 50.0% < Ni < 55.0%; traces < B < 0.006%; the remainder being Fe and impurities resulting from the elaboration. Nuclear reactor components, particularly those in nuclear fuel assemblies, are often of limited size and thickness. Many of these components are manufactured by forming one or more metal sheets. Such components require particularly high dimensional accuracy. In addition, the environment of a light water nuclear reactor is very specific and imposes very specific stresses on alloy 718, linked in particular to radioactivity. Light water nuclear reactor components are particularly exposed to the risk of environmentally assisted cracking, and in particular to the risk of stress corrosion cracking. US5244515 and US5047093 propose a high temperature heat treatment or “annealing” to slow the propagation of stress corrosion cracks in a 718 alloy used in a nuclear application, to reduce the occurrence of phase 5 in the microstructure in the 718 alloy. US8470106 discloses an environmentally assisted cracking desensitization anneal, the desensitization anneal being performed under a hydrogen atmosphere and aimed at eliminating as much interstitial elements in the 718 alloy as possible. One of the aims of the invention is to make it possible to obtain an alloy whose resistance to environmentally assisted cracking, particularly in conditions likely to lead to stress corrosion, is improved, while preserving the mechanical properties, particularly in the aged state. For this purpose, the invention proposes a method for manufacturing a component of a nuclear reactor, in particular a light water nuclear reactor, the manufacturing method comprising the steps of: obtaining a strip made of a nickel-based alloy of chemical composition, expressed in weight percentages: traces < C < 0.08%; traces < Mn < 0.35%; traces < Si < 0.35%; traces < P < 0.015%; traces < S < 0.015%; 17.0% < Cr < 21.0%; traces < Co < 1.0%; 2.80 < Mo < 3.30%; 4.75% < Nb + Ta < 5.50%; 0.65% < Ti < 1.15%; 0.20% < Al < 0.80%; traces < Cu < 0.30%; 50.0% < Ni < 55.0%; traces < B < 0.006%; the remainder being Fe and impurities resulting from the elaboration; carrying out a desensitization annealing of the strip in a static furnace to obtain an annealed strip, comprising maintaining the strip at an annealing temperature equal to or greater than 900°C, in particular equal to or greater than 920°C, preferably equal to or greater than 940°C and/or equal to or less than 1050°C, in particular equal to or less than 1000°C, preferably equal to or less than 980°C, for an annealing time equal to or greater than 1 min, in particular equal to or greater than 15 min, preferably equal to or greater than 30 min and/or equal to or less than 180 min; and shaping the annealed strip to obtain the component. Annealing alloy 718 in the form of a metal strip and before shaping the strip, at a limited temperature and with an appropriate duration, makes it possible to increase the phase 5 content of the microstructure of alloy 718. It was found that such an increase in phase 5 content helps to decrease the sensitivity to environmentally assisted cracking. The increase in the phase 5 content does not significantly degrade the ductility at room temperature of the 718 alloy obtained for easy forming, with a high value, which can reach up to 40% or even more, for the elongation at break. This has the advantage of maintaining low stress on the hot and cold processing tools and/or thus allowing better dimensional accuracy of the strip. This good dimensional accuracy is important to obtain, particularly on nuclear fuel assembly components. Carrying out the final solution annealing step in a static furnace and on the metal strip, preferably packaged in a coil, makes it possible to promote the appearance of phase 5 in a controlled manner, with economical implementation. The strip is processed as a whole before the strip is shaped to form a component, and preferably multiple components. Carrying out the annealing step on the strip, i.e. after the transformation steps necessary to obtain t