Surfi-Sculpt is a revolutionary new materials processing technology recently developed at TWI [1] . Using a power beam, a material can be processed to give a number of different types of feature or surface type. Presently, electron beams are preferred for this process because only they can easily be manipulated in the ways required to carry out the Surfi-Sculpt process properly. It is thought that this is likely to remain the case for most applications, unless there are spectacular breakthroughs in laser beam technology in the near future.
Surfi-Sculpt works by:
- melting substrate material using the heating action of the beam on the substrate;
- displacing material using the combined effects of temperature-variant surface tension and vapour pressure at the point of action of the beam;
- repeating or overlapping 1, 2 above to give features of the desired aspect ratio.
These steps may sound straightforward, and in a sense they are, inasmuch as once a Surfi-Sculpt 'recipe' to give a particular effect is developed, it may be repeated to give the same result many times over, with ease. However, the successful development of both the basic process in the first instance, and any particular 'recipe' that is required, is not trivial. Significant advances in both beam generation and beam deflection technology have been required in order to produce successfully the results to date.
The most obvious effect of this technique is usually to form a series of protrusions above the original surface. However, the material that forms the protrusions comes from intrusions, or cavities in the substrate. These may be broad and shallow, or they may be of very high aspect ratio, as many of the desired protrusions types are. They may even penetrate the work altogether, giving burr-free perforations of controlled shape.
To the left, a multi-faceted protrusion, in stainless steel. On the right, the reverse side of a titanium sheet, with cruciform, burr-free perforations, again made via the Surfi-Sculpt process.
Various techniques can be used to add materials to the workpiece before or during execution of the process, in order to render the processed material wholly or partially different in composition and/or properties. These techniques include pre-placed material, e.g. in the form of coatings, or the addition of material in the form of powder, wire, ion bombardment, plasma, sputtering, etc.
Surfi-Sculpt is a relatively rapid process. The features are usually formed in groups, rather than individually; during the formation of a single group, the beam is resident at each feature for only a small proportion of the time. A group of several hundred features may be formed by a single beam in about ten seconds, meaning that the time taken per feature is typically just a few milliseconds. The present development equipment is fitted with a single beam generator, but the process may ultimately be industrially applied by using many beams which are applied simultaneously.
Surfi-Sculpt works on a wide variety of materials, not just metals. Any material that forms a stable liquid phase under the action of the beam may be processed, and this includes some materials that are not electrically conductive in the normal sense.
The Surfi-Sculpt process is capable of making the following feature types:
- High aspect ratio blade-like protrusions (typically ~15 : 1, height : width).
- High aspect ratio columnar protrusions (typically ~10 : 1, height : width).
- Blind hole-type intrusions.
- Blind slot-type intrusions.
- Penetrating hole-type intrusions, with burr-free edges on the penetrating side.
- Penetrating slot-type intrusions, with burr-free edges on the penetrating side.
- Shaped protrusions, of high aspect ratio in one elevation.
- Curved blade-like protrusions.
- Multi-faceted protrusions.
- Angled protrusions.
- Multi-faceted (intersecting) slot-type intrusions.
- Curved, slot-type intrusions.
- Angled intrusions.
- Composite protrusions in a new functional alloy or alloys.
Any of these features may be combined in a single or successive treatments to give the desired result.
Some Surfi-Sculpt applications under development include the following:
- composite to metal bonding, also known as ComeldTM
- promotion of adhesive bonding
- bonding and direct moulding of polymers to metal parts
- manufacture of aerodynamically enhanced surfaces
- manufacture of hydrodynamically enhanced surfaces
- manufacture of mechanically keyed surfaces
- manufacture of filters, and other applications requiring shaped slots and holes, e.g. for mixing of gases and/or liquids
- manufacture of surfaces with enhanced thermal properties
- manufacture of tailored surfaces with specific wave interaction, absorption, emission and/or propagation properties
- manufacture of locally alloyed functional surfaces with specific mechanical, electrical, magnetic, thermal chemical, etc properties.
TWI would welcome collaboration with potential industrial users of the technology in any of the above application areas.
Further information
For further details please contact us.
Reference
- Dance, BGI, Kellar, EJC: 'Workpiece Structure Modification'. International Patent Publication Number WO 2004/028731 A1.