Changes of stainless steels surface morphology as a result of interaction with intense pulsed plasma beams containing ions of rare earth elements
Stainless steels are used in numerous industrial applications, mainly due to their excellent corrosion resistance. However, in many cases their low hardness and poor tribological properties impose strong limitations. On the other hand, there are many examples that require the use of electrolyte corrosion and high temperature corrosion resistant materials, which at the same time exhibit good wear resistance. Examples of such applications include liquid flow sensors, temperature, pressure and humidity sensors for aggressive environments, interconnectors for solid oxide fuel cells (SOFC) etc. In all these cases stainless steels are frequently used. The beneficial effect of active elements with high oxygen affinity, such as yttrium, cerium, lanthanum and other rare earth elements (REE) on high temperature oxidation resistance and corrosion resistance against aggressive media has already been studied, e.g. [1, 2]. In addition, these elements added to the bulk alloys or to their surfaces dramatically improve the oxide scale adherence [4]. On the other hand, it is known from our recent study that the surface modification process using intense plasma pulsed leads to improvement of the tribological properties of unalloyed steels [5–7]. Pulsed-plasma treatment – a procedure developed at the Soltan Institute for Nuclear Studies (SINS) Świerk, Poland, consists in treating a solid with plasma pulses of Changes of stainless steels surface morphology as a result of interaction with intense pulsed plasma beams containing ions of rare earth elements Bozena Sartowska, Jerzy Piekoszewski, Lech Waliś, Elzbieta Skladnik-Sadowska, Marek Barlak
Modifications of the stainless steels passive film induced by cerium implantation
In this work X-ray photoelectron spectroscopy studies and cyclic voltammetry are combined to elucidate the effect of Ce implantation on the formation and evolution of passive layers generated on AISI 430 and AISI 304L steels in alkaline medium. The passive films develop in implanted steels result thinner and less defective than in unimplanted. This result is interpreted in terms of a cerium-induced inhibition of the passive film re-oxidation (formation of iron and chromium oxides). The main difference between the behaviour of the two types of steel (ferritic and austenitic) seems to be related to the enrichment in nickel promoted by cerium in the outermost layer of AISI 304L.
The Role of active elements in the oxidation behaviour of high temperature metals and alloys
Metals and alloys rely for their application at high temperature on the formation and retention of oxide scales, which act as a barrier between the metallic substrate and the reactive species in the environment such as 0, S, N, C, Cl, etc. This protection concept requires that the oxide grows slowly, develops a dense, uniform layer, is well adherent, has sufficient ductility to accom modate plastic deformation of the substrate and is resistant to thermal cycling. For many years it has been known that small concentrations of certain "active elements" such as Y and the rare earths, as well as carbon and sulphur, can exercise a significant influence upon the oxidation! corrosion behaviour of high temperature metals and alloys. An increasing number of experimental studies on this topic have been published recently. However no generally accepted understanding with regard to the detailed mechanisms and the way in which alloy composition and structure, temperature and environmental conditions, etc., are interacting has yet been achieved, although many - often controversial - theories and ideas have been presented. It therefore seemed to be an appropriate time to bring together a group of experts to review and evaluate the current state-of-the-art and to discuss various aspects of this important topic."