Distinctive features of sputtering of Fe?Cr?Ni alloys containing heavy-element alloying constituents

Abstract

The properties of steel can be controlled over a wide range through the introduction of alloying constituents. In particular, the addition of molybdenum to steel helps make it more heat~resistant and, hence, more promising as a material for the first wall in a hightemperature thermonuclear reactor. However, the entry of heavy-element impurities into a plasma leads to an increase in radiation losses and at a concentration of 0.6% Mo and 0.2% W the radiated power becomes comparable with the energy released by s-particles in the fusion reaction [i]. In view of this, the use of steels that contain several percent molybdenum and tungsten as the material for the first wall of a thermonuclear reactor seems, at first glance, to be inadmissible since during bombardment of a multicomponent alloy with accelerated ions or atoms the flux of sputtered particles should have the same composition as the sputtered target. A process of selective sputtering inevitably causes a change in the composition of the surface layers of multicomponent materials irradiated, if their constituents are characterized by different sputtering rates or different mass numbers. A number of studies [2, 3] have discovered that the processes of selective sputtering and radiationinduced segregation of admixtures in alloys are superimposed and as a result the constituents are redistributed considerably near the surface in comparison with their initial content.