Back on the rails

Broken train tracks begone! A new approach to fixing damaged rails in remote locations has proved viable for large-scale use, according to a study published in The Journal of Materials Processing Technology.

Researchers and engineers from Monash University, the Australian Nuclear Science and Technology Organisation (ANSTO) and the Institute of Railway Technology (IRT) have developed a reliable and efficient laser-based rail repair technology using neutron scattering experiments.

This could increase the service life of rails and reduce maintenance time and costs, especially on regional train tracks.

A n illustration of a p-shaped object. It is green with red on top
This image depicts residual stresses created by the heat generated by the laser during the cladding deposition process on the rail. Credit: Institute of Railway Technology/Monash University/ANSTO

Using a special nuclear technique at ANSTO, they established the method to repair high-value components of railway tracks. The technique is called laser cladding, and involves coating damaged rail surfaces with a stainless steel or a cobalt-based alloy in single or double layers with laser technology.

“Laser cladding can deposit these beneficial materials onto damaged areas but can also introduce or re-distribute residual stresses,” explains study author Taposh Roy, a project engineer with Melbourne Metro Trains.

Extra damage can come from subjecting rails to the high temperatures during laser cladding, so the team developed a new procedure to evaluate residual stresses in thick sections of full-scale cladded rails.

“Only neutrons can penetrate through the deep surface of the rail material and measure full triaxial stress distribution non-destructively with little preparation,” says Roy.

“We found that the application of a post cladding heat treatment significantly reduced the residual stresses from the surface and the subsurface of the cladded rails.”

The method appears to be superior to conventional cladding – arc weld methods – that are common today.

“These successful in-house repair trials are very encouraging to explore further the application of this technology as a portable and mobilised unit, that can be deployed to address the rail maintenance problems in remote areas of Australia,” says Professor Anna Paradowska, of the Australian Centre for Neutron Scattering and conjoint professor at The University of Sydney.

This experiment was confined to the laboratory, so the next step is to test the method “in the wild” to see whether it is appropriate for rails that are currently being used.

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