SURFACE TREATMENT
place is actually between laser technologies as a whole and the conventional cladding methods still used, such as arc and spray-based technologies. ‘Te costs of these traditional cladding
methods are comparably smaller than using lasers. However, with the decreasing investment prices of fibre and diode laser technologies, the lasers could capture market share,’ Gaebler said. Traditional cladding methods, while being
more cost effective, oſten result in mixtures between the original base material and the cladding material, which can prevent a pristine surface being created and lead to more layers being needed. ‘With laser cladding it’s not necessary to add
these extra layers, as very little mixture occurs with the base material; this saves a lot of time in the process,’ said Gaebler. ‘Te other advantage is the reduced thermal impact offered by lasers, which provides a higher quality cladding and avoids the distortions seen when using arc-based technologies.’
Cost over quality Fibre lasers and disk lasers, while offering a better beam quality than diode lasers, do not necessarily make the best tools for cladding, according to Gaebler. ‘Laser cladding doesn’t necessarily require a high-quality gaussian beam; you can get away with a top hat profile, which may actually be preferred for some applications,’ he said. Surface treatments can range from
processing in the millimetre range, to applying coatings to very large surfaces found on oil and gas shaſts and hydraulics. ‘As a laser manufacturer you have to be able to deal with both types of application: the large area cladding with high deposition rates at very high speeds, plus the fine detail cladding,’ said Gaebler. Coherent has therefore chosen
Engineering manager Andres Veldman from IHC Vremac Cylinders and Fraunhofer ILT’s Thomas Schopphoven (left) prepare the way for EHLA in series application
enables it to clad large areas at high speeds, making it suitable for applications in the oil and gas or mining industries. Alternatively the company’s fibre-coupled DF-series is better suited to performing finer-detailed cladding applications in multiple directions, making it ideal for repairing tools. ‘You cannot have this variety with fibre
applications can be done with diode lasers. We think they’re the best choice
Most cladding
to follow the transition to diode lasers and supply both fibre-coupled and free space sources – rather than fibre or disk lasers – for cladding, emphasising the benefits of a lower cost of ownership and simpler design over higher beam quality. ‘Most cladding applications can be done with diode lasers,’ commented Gaebler. ‘We think they’re the best choice for this application.’ Te lack of fibre coupling in Coherent’s free space diode offering, the HighLight D-series,
14 LASER SYSTEMS EUROPE ISSUE 37 • WINTER 2017
lasers,’ said Gaebler. ‘You would have to design an optic that takes the smaller beam of 100 to 400µm and spread it out over a beam profile of around 6 x 36mm, which is expensive. With direct diode lasers you can simply get this beam profile out of the array; it’s much simpler to implement.’ Coherent is now considering higher power fibre-coupled diode lasers for cladding, improving on its current 6 to 8kW offerings. Despite their processing
capability already being sufficient for most cladding applications,
certain optics are currently being explored in industry in order to enhance the beam quality of diode lasers, according to Gaebler. Te market is yet to determine, however, whether these optics could be more beneficial than the fibre technologies already in use. Tese developments are being made on top of the general ongoing improvements in lasers in terms of footprint, cost of ownership, serviceability and lifetime.
Improving all round Te laser source is only one part of a cladding system. Gaebler commented: ‘Looking at the cladding process itself, most things are happening in the head, with more sensors [being added].’ With the upcoming demand for smart
manufacturing in Industry 4.0 environments, there will be an increasing need for laser companies to offer additional sensors that monitor laser parameters – such as beam quality and power measurement – and convey them to machines that offer feedback about the status of the equipment. Automated predictive maintenance could ensure that end users are achieving the maximum uptime with their products. Improvements are also having to be made in
cladding soſtware, according to Hauser of TWI, as the complexity of surfaces in need of processing is increasing, which has proven particularly challenging with the current programmes available. ‘One of the issues is that the soſtware used
isn’t advancing as much as it perhaps should at the moment,’ he said. ‘Tere are key soſtware houses working to produce soſtware for laser cladding, but because of the diversity of laser metal deposition – it’s used for 3D printing, coatings, repair, etc – there’s no soſtware package that’s available for everything.’ Te challenge, according to Hauser, is that a lot of the soſtware currently in use has
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www.lasersystemseurope.com
Fraunhofer-Gesellschaft
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