Australian researchers have developed laser cladding technology that could be used for the large-scale repair of damaged railways in remote locations.
The technology, described in the Journal of Materials Processing Technology, could increase the service life of rails and reduce maintenance time and costs, as repairing rails is preferable to replacing them.
Heavy haul rails repairs present significant challenges as they cannot be performed in the controlled environment of a factory, but rather need to be done in remote areas, for example the Australian outback.
Which is why the researchers, from Monash University and the Australian Nuclear Science and Technology Organisation (ANSTO), collaborated with engineers from the Institute of Railway Technology (IRT) and commercial firm Hardchrome Engineering, to develop a reliable and efficient laser cladding repair technology.
With the technology, the damaged rail surface can be coated with a stainless steel or cobalt-based alloy in single or double layers, reducing or mitigating detrimental stresses from critical regions of the repair.
'Laser cladding can deposit these beneficial materials onto damaged areas, but can also introduce or re-distribute residual stresses,' confirmed Taposh Roy, a Monash PhD graduate and currently a project engineer at Melbourne Metro Trains.
According to the researchers, the method appears to be superior to conventional arc-weld-based cladding methods, currently the most common techniques for repairing wear damage in rails.
Residual stresses created by the heat of a laser during cladding deposition. (Image: Ansto)
In developing the new technology, the researchers used neutron scattering on a full-scale railhead in order to measure residual stresses created by the heat of the laser during the cladding deposition process (pictured above).
As part of this, 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' said Roy.
To acquire measurements in small gauge volumes on a large path length through the steel, they made blind holes in the sample. Taking measurement at the middle of the two holes also avoided a disturbance of local stresses.
'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,' said Roy.
The research was a finalist in ANSTO’s Neutron and Deuteration Impact Awards, demonstrating its relevance to transport – one of Australia’s research priorities.
'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,' said Professor Anna Paradowska, industry engagement manager at the Australian Centre for Neutron Scattering, and conjoint professor at The University of Sydney.