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
A possible thermodynamic mechanism of craters formation on metal surfaces caused by intense pulsed ion beams
Abstract It was found that some craters appeared on the irradiated surfaces that have been melted under intense pulsed ion beam (IPIB) irradiation. These craters with various sizes and morphologies limit the utilization of IPIB as a novel means of surface processing in some cases. In this work we examined surfaces of 45 # steel and Ni 3 Al samples irradiated with IPIB at different beam parameters with scanning electronic microscopy (SEM) and energy dispersive spectrometry (EDS), and found that the craters basically can be sorted into two groups. The first kind of craters directly relates to droplet from the ion source, and the other kind of craters is due to the non-equilibrium process of ultra fast quenching. According to the dynamic theory of interaction between ions and materials and the thermodynamic theory about defects, a possible forming mechanisms for the second kind of craters is proposed in this paper. The vacancy densities produced in IPIB irradiation at various pulse parameters are calculated. Moreover, the process of cratering is analyzed in detail, and the variety of the crater morphologies is discussed.
Neutron Residual Stress Measurements on Rail Sections for Different Production Conditions
Rail sectioning with subsequent neutron diffraction experiments has been used to assess residual stresses in the rails. In this study we present the results of neutron stress measurements performed at the NIST Center for Neutron Research (NCNR) on rail sections from rails that were produced under various conditions. Specifically, these are air-cooled, air-cooled and roller-straightened, head-hardened and head-hardened and roller-straightened. More significantly, a head-hardened and roller-straightened rail was also studied after service to elucidate evolution of the service-induced residual stresses. In the latter case both a transverse-cut slice and the central region of a 0.53 m long piece were studied. Measurements on this piece are the first in which triaxial stresses have been determined for an intact rail. Neutron strain measurements with 3×3×3 mm3 spatial resolution were successfully employed for transversally cut slices to verify the difference in the stress state depending on the production process. Although examination of slices allows determination of only two-dimensional stresses in the plane of the slice, additional measurements on obliquely-cut slices, which were also carried out, and utilization of FEM gives the possibility of reconstructing the full triaxial stress distribution. Together, these approaches provide a better understanding of rail fabrication and the possibility of improving the durability and safety of rails in the future.Copyright © 2004 by ASME