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Title: Recrystallization and modification of the stainless-steel surface relief under photonic heat load in powerful plasma discharges

Targets made of ITER-grade 316L(N)-IG stainless steel and Russian-grade 12Cr18Ni10Ti stainless steel with a close composition were exposed at the QSPA-T plasma gun to plasma photonic radiation pulses simulating conditions of disruption mitigation in ITER. After a large number of pulses, modification of the stainless-steel surface was observed, such as the formation of a wavy structure, irregular roughness, and cracks on the target surface. X-ray and optic microscopic analyses of targets revealed changes in the orientation and dimensions of crystallites (grains) over a depth of up to 20 μm for 316L(N)-IG stainless steel after 200 pulses and up to 40 μm for 12Cr18Ni10Ti stainless steel after 50 pulses, which is significantly larger than the depth of the layer melted in one pulse (∼10 μm). In a series of 200 tests of ITER-grade 316L(N)-IG ITER stainless steel, a linear increase in the height of irregularity (roughness) with increasing number of pulses at a rate of up to ∼1 μm per pulse was observed. No alteration in the chemical composition of the stainless-steel surface in the series of tests was revealed. A model is developed that describes the formation of wavy irregularities on the melted metal surface with allowance for the nonlinearmore » stage of instability of the melted layer with a vapor/plasma flow above it. A decisive factor in this case is the viscous flow of the melted metal from the troughs to tops of the wavy structure. The model predicts saturation of the growth of the wavy structure when its amplitude becomes comparable with its wavelength. Approaches to describing the observed stochastic relief and roughness of the stainless-steel surface formed in the series of tests are considered. The recurrence of the melting-solidification process in which mechanisms of the hill growth compete with the spreading of the material from the hills can result in the formation of a stochastic relief.« less
Authors:
;  [1] ;  [2] ; ;  [3] ;  [4] ;  [5] ;  [6] ; ;  [1] ; ; ;  [3]
  1. National Research Centre Kurchatov Institute (Russian Federation)
  2. Project Center ITER (Russian Federation)
  3. Troitsk Institute for Innovation and Fusion Research (Russian Federation)
  4. ITER Organization (France)
  5. EURATOM Association, Forschungszentrum Jülich GmbH (Germany)
  6. IHM, Karlsruhe Institute of Technology (Germany)
Publication Date:
OSTI Identifier:
22216064
Resource Type:
Journal Article
Resource Relation:
Journal Name: Plasma Physics Reports; Journal Volume: 39; Journal Issue: 11; Other Information: Copyright (c) 2013 Pleiades Publishing, Ltd.; http://www.springer-ny.com; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CHEMICAL COMPOSITION; COMPARATIVE EVALUATIONS; CRACKS; HEATING LOAD; ITER TOKAMAK; MELTING; METALS; MODIFICATIONS; NONLINEAR PROBLEMS; PLASMA GUNS; PULSES; RECRYSTALLIZATION; ROUGHNESS; STAINLESS STEELS; STOCHASTIC PROCESSES; SURFACES; VAPORS; VISCOUS FLOW; X RADIATION