Influence of Pulsed High Heat Fluxes upon the Material of Low Activation Austenitic Steel Tube in the Dense Plasma Focus Device

E. Demina (Sp), A.A. Balkov Institute of Metallurgy and Materials Science, Moskau (Russian Federation); S.A. Maslyaev, L.I. Ivanov, V. Pimenov, V.A. Gribkov, A.A. Baikov Institute of Metallurgy and Material Science RAS, Moscow (Russian Federation); A.V. Dubrovsky, Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Y.E. Ugaste, Tallinn Pedagogical University (Estonia); M. Scholz, R. Miklaszewski, Institute of Plasma Physics and Laser Microfusion, Warsaw (Poland); B. Kolman, ASCR, Prague (Czech Republic); S.I. Konyahin, Moscow State Institute of Electronics and Mathematics (Russian Federation) 
The characteristics of the material damage, structure change and distribution of the components in the surface layer of the low activated austenitic steel 25Cr12Mn20W under pulsed influence of deuterium ions and plasma beams have been determined for the hexahedral tube, which was placed in the cathode part of the Dense Plasma Focus device PF-1000 along the chamber axis. Irradiation of specimens was performed by microsecond high heat plasma and ions pulses with power density in the rang of GW per square cm.
It was found that conditions of interaction of the pulsed energy beams with material were different both for internal/external surfaces of the tube and for different parts of each facet. This fact resulted in different observed effects. As a rule in re-melted surface layers in addition to austenitic phase the martensite phase was observed. This phase transformation lead to increase of micro-hardness and strengthening of the layers. The action of extreme energy fluxes resulted in redistribution of the components of the steel in the surface layer and penetration of the copper into melted layer. These effects were observed for both internal and external surfaces of the tube. The most concentration of copper and carbon corresponded to the surface of the steel. It was found that content of manganese was lower and content of ferrum was higher in external surface layer in comparison with internal one.
In the “cold” part of the external surface of the tube the specific configuration of arrangement of the structural defects (bubbles and rings) was found.

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