Coatings are common in engineering applications for protecting the surface of components,
either from exposure to environmental conditions or from contact with other components. Laser
cladding is a coating technique which allows for thicker coatings of various alloys that enable
high load bearing interfaces to operate at a wider range of loads or for longer, for example by
increasing durability. This is of great benefit to the railways industry as well as other heavy
industries, such as the steel industry. Laser clad coatings have been used extensively in other
industries such as oil and gas for increasing the durability of drilling components; in mining
and earth moving equipment, for increasing the durability of the components that come in
contact with hard soil and rocks. Both are extreme interfaces.
In this study, new interfaces and extreme conditions for new industries are investigated, by
highlighting the laser clad coating advantages, when used under extreme conditions. The
extreme test conditions have not been investigated in published literature, especially with the
use of laser clad coatings.
This project evaluated the performance of laser cladding coatings on railway components such
as the wheel and rail. Other interfaces found in machinery in the steel industry were
considered, specifically in the rolling of steel. A variety of interfaces were evaluated by
modelling and testing, such as rolling-sliding, high pressure water jet erosion and impact.
Three clad materials were identified as suitable for the chosen interfaces, martensitic stainless
steel (MSS), Stellite 6 (Co-Cr) and a two-layer clad of Inconel 625 with Technolase. The clad
parameters were fixed, resulting in constant material grades, allowing the coatings used in
different interfaces to be comparable.
The materials choice was based on published research on similar interfaces. Tests were
performed on existing test rigs for rolling-sliding and bending tests. The impact test was
performed on a rig modified specifically for this study, while a bespoke rig was built for the
erosion test. Metallographic techniques were used for all materials, to prepare the samples for
characterisation using optical and electron microscopy, as well as nanoindentation and
microhardness. Pre- and post-test material analysis was performed.
The use of computer modelling was considered mainly for the generation of test parameters,
while the results from testing were compared to existing data. Key findings highlight that the
use of the selected clad materials under the chosen extreme interfaces can have a positive
effect on the durability of the coating, mainly by increasing the wear resistance properties of
the coating. Furthermore, the two-layer clad coating showed promising results in stopping
crack propagation to the substrate. The test results can be used in predictive tools by
researchers in academia, as well as in industry, as a way of introducing laser cladding
applications to interfaces of engineering products. Furthermore, the performance of the chosen
materials indicates that this study may be used as the basis for selecting similar clad coatings
for pilot trials or large scale testing.
