I keep hearing about ‘Surface Engineering’ but I’m not sure what it means or why it is important. Is it the same as metal finishing? Why does anybody do this, there seem to be very many options on offer, how can anyone choose the best option?

The essential definition of surface engineering is ‘the modification of the properties of a component surface to some advantage’. It is only done if there is real advantage or benefit as it is bound to add cost to the component. It will therefore only be done to gain an advantage.

If you think about it most of the interactions that a component has with its environment in service are on, or through, its surfaces. Usually, or very often, the component is made, for sound engineering reasons, from a material that does not intrinsically have the correct surface properties so it has to be ‘surface engineered’.

An example of this is the car body. This is usually made from pressed steel and is welded together. It has a sophisticated corrosion protection system that also provides the vitally important cosmetic finish. We can therefore say that a car body is ‘surface engineered’. It is correct to say that it has been painted, but that is only a part of the story, the steel probably has a zinc layer plated onto it followed by other layers with the paint as a final finishing layer or layers. It is better to think of this as an engineered system and this is why the term ‘surface engineering’ is growing in use.

There are hundreds, perhaps thousands even millions, of other components that are surface engineered. Problems of wear by many different mechanisms, corrosion often in combination are addressed every day. Here are just a few examples:

Airliners could not fly as gas turbines cannot work unless key components are properly treated and protected by surface engineering.

• The increased life and service intervals of vehicle engines and transmissions that we take for granted are provided, at least in part, by surface engineering.
• Many medical devices and prostheses are surface engineered to improve their compatibility with body tissue and to improve their lives and function.
• Your home is full of surface engineered objects such as the plated taps in your bathroom and kitchen, the handles on appliances, doors and furniture to say nothing of the paint on the doors and other woodwork. Even your razor blades are surface engineered!

Surface engineering is therefore application or problem oriented and the choice of the best solution is in reality an engineering decision. It is therefore necessary to consider the surface properties at the initial design stage rather than at the end of the process, or even after the parts are in production. Seek to understand the likely interactions between the part and its operating environment, identify what properties will be required and select appropriate treatments to provide those properties.

Remember that the substrate, the surface and the operating environment are a system, they must all be right for the application and each other. If they are not all right for each other then failure is inevitable. Of course the consequences of failure vary enormously, in a jet engine they can be catastrophic, in your motor car very expensive but on your razor blade merely an indication that you need a new blade!

Further information

Surface Engineering Division

Materials World September 2008 - focus on Surface Engineering