Phase transitions in Nb rich coating produced by laser alloying : a synchrotron radiation diffraction study.

Abstract

A great variety of studies have been performed in order to develop new materials with high performance in many adverse conditions such as wear and corrosive environment coupled with high temperatures and high stress levels. A strong scientific and technical effort is currently dedicated to develop wear and corrosion resistant surfaces to provide components having good behavior in such extreme working conditions, we have chosen laser alloying and prepared Nb rich coatings upon a nodular cast iron microstructure. The new tailored material is in fact a composite having a very hard coating covering a traditional iron base material. If the material is submitted for thermal cycling, it is imperative to know the phase transformations during heating/cooling cycles, as well as, during long periods of permanence at high temperatures. According to these guidelines, we performed an X-ray diffraction (XRD) study using the XRD beam line of the National Synchrotron Light Laboratory (LNLS, Brazil). The analysis of the XRD pattern indicates the presence of niobium and niobium carbides (Nb, NbC, Nb2C) from room temperature up to 750°C.