Investigation of ferromagnetic phase precipitation on the surface of some constructional materials for thermonuclear reactors

Abstract

Austenitic stainless steels are considered as a prospective material for the first wall of the thermonuclear reactors. Radiation and temperature influence erosion of material, and contamination of the plasma.This paper describes the results of investigations on the process of ferromagnetic layer formation on the surface of Cr-Mn and Cr-Ni austenitic steels after annealing at the working temperatures of the first wall (≈ 500°C) or at high temperature (≈ 1000°C), which can arise on the surface of blisters.The results of magneto-optic studies show that in the original samples with electropolished surface the ferromagnetic phase precipitations are absent. Ferromagnetic α-phase forms on the surface of Cr-Mn steel after heat treatment in high vacuum as a result of selective evaporation of the austenizing components. The parameters of evaporation of these components were investigated using thermogravimetry, and the re-distribution of the elements in the surface layers were studied by Auger electron spectroscopy.From these results it can be concluded that thin ferromagnetic layers can be formed on the surface of constructional materials during the reactor's run. This layer must be considered in calculations of the configuration of magnetic fields, working regimes of thermonuclear reactors, and plasma stability.