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Technical Insight: Surfi-Sculpt

Developed at TWI, Surfi-Sculpt is a revolutionary materials processing technology that uses a power beam to generate precisely defined, textured surfaces. Both laser and electron beam variants have been developed, although both types involve a similar process.

The laser or electron beam is deflected rapidly over the surface of a substrate where it displaces material from the surface. Working in a controlled manner, this displacement leaves protrusions and intrusions across the surface of the material surface. Spikes of up to 2mm in height as well as blades, channels, swirls and burr-free holes in a range of metals, polymers, ceramics and glasses. The process takes just a matter of seconds per square centimetre with the size, shape and distribution of the features all able to be varied to produce a surface tailored for specific applications.

Core Research Programme (CRP)

Through the core research programme (CRP), TWI conducts projects to address challenges faced by our Industrial Members, advancing technologies and processes, and finding new solutions for industry problems. These projects are jointly funded by our Industrial Members, with the outcomes made available to all our Members.

- Laser Surface Modification Using the Surfi-Sculpt Process

This 2009 CRP was created to extend Surfi-Sculpt from an electron beam-based process by demonstrating the process using laser beams before comparing the results with electron beam produced Surfi-Sculpt surfacing. This project took advantage of developments in laser materials processing at the time, the use of high brightness fibre-delivered laser beams that allow a high-power density focus onto a small area from a relatively long distance as well as recently developed laser beam scanning systems. For this work, both disc and fibre laser beams were used at relatively modest laser powers of less than 2kW, along with two different, commercially available laser beam scanning systems that had originally been developed primarily for laser welding applications in the automotive sector.

- Optimisation and Observation of the Laser Surfi-Sculpt® Process

With the 2009 CRP project having investigated the use of laser beam technology for the Surfi-Sculpt process, this 2013 project aimed to further optimise the process. As well as creating textured protrusions above the original surface and a corresponding array of intrusions in the substrate, the beam can be moved in a third, (z) axis direction by linearly moving a focusing lens within the mirror scanning system to introduce a further experimental variable. This project tested higher power lasers than had been used in previous work while the scanner processes other features within an array, during the delay periods required for cooling of the samples. Using our existing knowledge of preferential processing conditions coupled with high-speed imaging (HSI) and thermal analysis techniques, an additional goal of the project was to gain a greater understanding of the physical phenomena involved in the process, so that this knowledge could be applied to industry. The project developed optimum Surfi-Sculpt® processing parameters for Ti-6Al-4V and stainless steel 304 while also improving production rates through intelligent programming of the scanning software. The use of the z-position during feature build helped extend the range of features produced by the laser technique. This work further enhanced TWI’s understanding of the Surfi-Sculpt® process using high speed and thermal imaging.

- Electron Beam Surfi-Sculpt® Process and Mechanisms

By 2018, our experts had returned to the topic of electron beam Surfi-Sculpt for a new CRP. TWI used slow motion analysis to provide a greater understanding of the process (Figures 1-2). This highlighted four distinct phases for the formation of a Surfi-Sculpt feature as well as showing that the initial movement of molten material caused by interaction with the beam is more controlled using electron beams than when using lasers. Heat exchanger testing with the use of Surfi-Sculpt showed an approximate doubling of the heat transfer coefficient when compared to a conventional design at a similar pressure drop and a 1000w heat load. Surfi-Sculpt was also able to maintain the operating temperature of a power resistor 30 degrees lower than with a conventional design. The process was also assessed in relation to composite to metal joining to improve lay up and ensure no voids are left.

Dedicated Industrial Member Support and Other Projects

Much of the work undertaken at TWI is conducted confidentially on behalf of individual Industrial Member companies. Such dedicated work also feeds into the knowledge held at TWI across all industry sectors and highlights needs and challenges faced by a range of industries. In relation to Surfi-Sculpt, our experts used the process to address composite-to-metal joining, creating the ‘ComeldTM’ solution…

- Metal to Composite Joining Breaches a New Frontier

This work sought to provide improved composite-to-metal joining so that the high strength and low weight benefits of fibre reinforced polymers could be better realised when joined to metals. Poor mechanical performance, low fatigue resistance, and a distrust of repeatability and joint integrity had created an atmosphere of over-conservatism in the use of composite-to-metal joins, which was negating many of the benefits of the materials.

The use of Surfi-Sculpt as a metal pre-treatment process (Figure 3) to create an improved bond between the polyester resin and the prepared surface (Figure 4). This process, dubbed ComeldTM, led to joints failing at much higher loads and with the absorbing of far more energy before failure than with a conventional joint of identical dimensions.

To find out more about the Surfi-Sculpt process and the support available at TWI, please see here:

https://www.twi-global.com/who-we-are/innovation/intellectual-property-licensing/surfi-sculpt

Figure 1. Cone shaped features on 5mm Ti-6Al-4V substrate
Figure 1. Cone shaped features on 5mm Ti-6Al-4V substrate
Figure 2. Ridge features on 6mm Al6082-T6 substrate
Figure 2. Ridge features on 6mm Al6082-T6 substrate
Figure 3. The pretreated metal
Figure 3. The pretreated metal
Figure 4. A Comeld joint
Figure 4. A Comeld joint
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