Arunim Ray B.E., M.Tech Darwin College University of Cambridge Materials Science and Metallurgy 27 Charles Babbage Road, Cambridge, CB3 0FS, U. K. ar724@cam.ac.uk +44 1223 334336 Publications

Niobium microalloyed rails

Certain railway systems are not well maintained and yet investments are planned for heavy ore transportation projects. Rail steels rely primarily on their properties on wear and rolling-contact fatigue resistance. These properties, together with the toughness, can in principle be optimised by implementing thermomechanical processing during the manufacture of the rails, assisted by controlled additions of niobium as a microalloying solute.

The purpose of my current work is to develop an alloy design for rails that conciliates the highest values of wear resistance, rolling contact fatigue and toughness by niobium micro-alloying. One of the major difficulties is to ensure that the microalloying addition does not segregrate during the manufacture of the steel, since niobium is a strong carbide former and rail steels traditionally require large concentrations of carbon. An attempt is being made to create a microalloying strategy in the context of standard rail production methods, including the fact that deformation through the section of the rail will not be homogeneous. This work involves design of a thermomechanical processing route, detailed calculations of phase diagrams, kinetics of transformations, and advanced characterisation methods such as high-resolution transmission electron microscopy and microanalysis, and complex mechanical tests including rolling contact fatigue and wear assessments.

My research is funded by CBMM, Brazil.