Increasing functionality with structured surfaces

Thanks to recent breakthroughs in the area of laser technology and ECM it has become easier to give components and tools increased functionality. This is done by texturing or giving structure to surfaces.

A keynote presentation at the 2016 High Performance Cutting Congress (Chemnitz, Germany) dealt with the possibilities for increasing the functionality of components and tools through texturing and giving structure to surfaces. This has become easier thanks to recent breakthroughs in laser technology and ECM that are gaining international recognition. The German Fraunhofer Institut in Chemnitz (IWU) has already carried out work in this area, specifically in being able to demonstrate the opportunities presented by certain applications.  

Surface and functionality

The surface of a component can influence its functionality in different ways. For example this thin zone can influence resistance to corrosion, the frictional coefficient, the optical properties, wetting, the bio-compatibility and the thermal conductivity of a component. Often, and quite rightly, coatings are used to improve the properties of a surface. For example TiN and TiCN to a thickness of just a few microns is used to improve wear resistance. However this method is not always possible in every situation and for every application. But giving it a surface texture or structure can provide an ideal solution.

The research mainly involved applying microstructures to two metal surfaces that were made to rub against each other in an oily environment. This is actually what happens in gearboxes where controlled friction is used for the function of the component. These microcavities were created by an 8 watt picosecond laser with a diameter of 50 µm and a depth of 10 µm.

Tests with bronze surfaces combined with steel opposing surfaces demonstrated that the microcavities in the steel retain oil and act as lubricant reservoirs, which in turn can reduce the frictional coefficient by more than 25 per cent. The wear on the bronze surfaces also reduced, thereby resulting in the lifespan of the item being increased.

Sirris goes further into laser texturing

Depending on the application, the functionality can be altered by applying various textures. This means for example that surfaces can be given higher frictional coefficients, or be made water repellent. Sirris has already carried out a number of exploratory tests in these areas and intends to continue with this research in future. This will mean setting up their own research programme with investments in femtosecond laser texturing machines. Based at the Sirris department at Diepenbeek the machine will be available from November 2016. More about this later!

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