Program package CONFIT enables a complex processing of 57Fe and 119mSn Mossbauer spectra. The mouse drag-and-drop technique is used to set up the background and parameters of the individual spectral components according to the structural model supposed. An original method has been applied: a nonlinear least-squares procedure with the Fast Fourier Transform (FFT) technique. A combination with improved matrix formalism can create various physical models to analyze the measured experimental data in a proper way. The hyperfine field distribution(s) and also quadrupole splitting distribution(s) with Gaussian profile can be applied, besides discrete components. The finite sample thickness can be included in terms of transmission integral and a dependence of the spectral line-width on its position with respect to the spectrum center is described by an additional parameter. This fitting procedure is suitable for Mossbauer spectra taken in the transmission and in the back-scattering geometry (including γ-ray and conversion electrons) and it can be successfully applied for analyzing the emission Mossbauer spectra. The transmission Mossbauer spectra yield information concerning the bulk microstructure, the back-scattering geometry is used for surface studies and the emission Mossbauer spectra yield information from grain boundaries or interface regions. The CONFIT is user friendly, fast and applicable for complicated Mossbauer spectra. Copyright © 2006 John Wiley & Sons, Ltd.

CONFIT: Mössbauer spectra fitting program

It is commonly believed that the white layer formed during machining of steels is caused primarily by a thermally induced phase transformation resulting from rapid heating and quenching. As a result, it is often assumed that if the temperature at the tool flank-workpiece interface exceeds the nominal phase transformation temperature for the steel, a white layer forms. However, no attempt has been made to actually measure the temperatures produced at the tool flank-workpiece interface and correlate it with microstructural evidence of phase transformation. This paper aims to address these limitations through suitably designed experiments and analysis. Orthogonal machining tests were performed on AISI 1045 annealed steel at different cutting speeds and tool flank wear. During machining, temperature measurements at the tool flank-workpiece interface were made using an exposed thermocouple technique. Metallographic studies of the machined sub-surface and X-ray diffraction (XRD) measurements were performed to determine the presence and depth of white layer, and the presence of the retained austenite phase in the machined surface layer, respectively. Analysis of the data shows that the white layer can form due to phase transformation at temperatures below the nominal austenitization temperature of the steel. Possible causes of this result are presented.

White layer formation due to phase transformation in orthogonal machining of AISI 1045 annealed steel

Early stages of rail squat formation and the role of a white etching layer

Improving wear resistance of rails has a direct impact on the performance of rail–wheel system in railroad technology. Enhancement of sliding wear resistance at curved track, where factors such as adhesion, high slip ratios and contact fatigue act at contact patch of rail–wheel system, is particularly desirable. In the present investigation, influence of laser surface modification on sliding wear performance of a pearlitic rail steel (used in Indian railways) under two different conditions, namely, laser hardening (without any melting involved) and laser melting (with thin surface layer melting), has been studied under laboratory conditions. Before sliding wear testing, the effect of laser scanning speed on the treated layer depth has been optimised, utilising a 9 kW CO2 laser system. Sliding wear tests were carried out using a pin-on-disc device, with laser treated and untreated pearlitic rail steel discs and sliding pins made of wheel steel material, tungsten carbide (WC) and high speed steel (H...

O. Schneeweiss

Papers

Microscopic investigation of surface layers on rails