Surfacing, or surface engineering, are used to describe the process of altering the surface characteristics of a component to achieve an improvement in surface properties. One goal is to make possible the design and manufacture of components with a combination of bulk and surface properties unobtainable in a component of single monolithic material.
There are numerous surfacing processes that can be used to deposit a coating or modify the surface structure. They range from the more traditional electroplating, weld overlaying, thermal spraying and thermochemical treatments (carburising, nitriding), to newer technologies such as physical vapour deposition (PVD), chemical vapour deposition (CVD), ion-implantation, laser surface modification, plasma thermochemical diffusion treatments and cold spraying.
Coating thickness varies from several millimetres for weld overlays to a few microns for PVD and CVD coatings; whilst the surface modification depth can vary from 0.5 microns or less for ion-implantation, up to more than a millimetre for nitriding. Likewise, the coating properties can vary considerably. For example, surface hardness can be modified to 1000HV for nitrided steels and up to 3500HV with the deposition of a TiN PVD coating.
Available coatings and treatments are so numerous, and still increasing, to make selection a difficult task for the non-specialist. Several alternative surface treatments can often provide acceptable solutions in a given application. Final selection must consider the cost and practicalities of the treatment, taking into account the composition, size and shape of the component concerned.
Further information
What is physical vapour deposition (PVD)?
What is chemical vapour deposition (CVD)?
What is a coating?
What is spraying?
What is hardfacing?
Surface engineering at TWI
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