A research project in Bern, Switzerland, is looking at the commercial viability of coating steel components such as train wheels to reduce urban noise.
Spray coatings specialist Sulzer Metco says the results of the study, involving Lausanne University and the municipal transport authority SVB, will be used to combat noise in applications such as industrial machines.
Vibration damping exploits a phenomenon known as magneto-elasticity. Alloys with this property are made up of magnetic domains, or Weiss blocks, separated by boundaries called Bloch walls. The domains act as cushions to absorb vibration by converting the mechanical vibrational energy into heat. The damping effect is enhanced by heat treatment of the material, which releases material stresses.
Vibration damping prolongs the life of the components and protects against corrosion.
In the Sulzer method, ferritic components are sprayed with a ferric-chromium-aluminium alloy before being heat treated.
The vacuum plasma spraying method achieves high density cohesion of the coating and the steel substrate. Particles hit the surface of the component at a velocity of more than 600m/sec in temperatures of around 16,000iC.
The treatment is said to contain noise frequencies within a bandwidth of 10-10kHz regardless of vibration frequency. This compares with up to 20kHz from uncoated wheels.