THE DIRECT-DIODE ADVANTAGE

“If you asked most people in my industry, and especially the vendors that sell this equipment, they would tell you that the best tool for a large area cladding shop is a bercoupled diode laser They would say you can take one ber-coupled diode laser and then connect it to various processing heads as needed to perform dierent jobs,” notes Daniel “But, as someone who has done a lot of laser cladding, I can tell you that is exactly the wrong answer The problem occurs with job changeovers If I’m doing one job with a 6mm long line beam, and the next job requires an 18 mm beam, then I have to change to a dierent cladding head That requires realignment and adjustment – and that takes time ”

“The common perception is that someone can buy a single ber-coupled diode-laser system and a bunch of dierent process heads and then they can do everything And maybe they can – but they can’t do it fast and eciently And when that equipment is down for changeovers, you’re not making money That limits your ability to do highspeed, large-area cladding,” he adds

“In contrast, using the HighLight DD, I just swap the optics in the process head to change line dimensions – and start the process again It literally only takes a moment And I can get laser lines long enough to clad even really large areas in a timeframe that makes economic sense ”

“Of course, I’m not saying there’s something wrong with ber coupled systems I have several myself and use them extensively They’re a cost-eective tool for cladding smaller areas on lower value parts But they don’t deliver the exibility that is often promised And they certainly aren’t the right for the large area cladding tasks that have become a big part of the business at APEX ETG They wouldn’t make economic sense for that ”

Cladding In Action

The 10 kW Coherent HighLight DD direct-diode laser has enabled APEX ETG to perform cladding jobs which have never been done before in Western Australia – and maybe nowhere else in the entire world One example is

“hardfacing” a mining excavator “bucket ” This is the huge scoop on the excavator that picks up earth The particular bucket presented to APEX ETG had a volume of 42 m³ –quite literally the size of a school bus

These buckets become worn through use and are eventually resurfaced with new material to keep them usable In the past, this meant welding thick chromium carbide/tungsten “wear plates” on to the bucket Each plate might be about 3mx1m, so quite a few are required to cover the entire bucket surface

But welding wear plates has some signicant drawbacks

First, it’s a time consuming and labor-intensive process

In all these processes, an arc melts the surface of the base material Cladding material is then introduced in either wire or powder form and is also melted by the arc It mixes with the molten part surface, and then resolidies to form the clad layer

Another approach is thermal spraying Here, the powdered clad material is melted by a ame or electricity, and then sprayed on to the workpiece The workpiece is only heated to <200°C The four most common types of thermal spraying are ame spraying, arc spraying, plasma spraying and high-velocity oxyfuel (HVOF)

Laser cladding is similar to arc welding methods The laser melts both the substrate surface and the clad material, which can be in wire, strip or powder form

However, laser cladding oers signicant advantages over all these other techniques Like welding methods, the laser clad layers make a true metallurgical bond with the substrate This means an extremely durable cladding layer, which won’t chip or delaminate, and which provides superb wear and corrosion resistance This isn’t the case with thermal spraying methods

However, unlike arc welding, the laser doesn’t signicantly heat the bulk of the part This avoids thermally induced part distortion, and the need for post-processing steps to correct for it The heating that occurs during arc welding can also cause volatile alloying elements to evaporate and may cause case hardening in some materials

Next, it adds a ton of extra weight to the bucket – or more precisely, 9 tons for the wear plate package for this particular bucket

Welding the at wear plates to the curved surface of the bucket creates some additional problems The plates are under stress (because they’re being bowed), and sometimes they spring back o during use This means excavator downtime while the plate is welded back on Plus, there’s a signicant safety issue A plate springs o with substantial force This has potential for injuring workers

To perform laser cladding, APEX ETG mounted the bucket on a large robotic platform This allowed the laser beam to move continuously and cover the entire surface with cladding This took much less time than a typical repair using welding

The entire amount of cladding material applied to the bucket weighed 450 kg This means that with every single scoop, the excavator can pick up an extra 8 5 tons compared to a bucket covered with wear plates This makes the equipment more ecient, and cuts fuel costs signicantly

The cladding applied with the direct-diode system doesn’t compromise on quality, either In fact, quite the opposite The bucket hardfaced at APEX ETG already has 5,000 operational hours on it, and there has been no eect on the laser clad surface Plus, there’s no safety concern with laser cladding because the new surface won’t spring o

“This job is an extreme example,” notes Rhind “It’s quite possibly the largest part ever clad And it would just be utterly impossible to get this same level of results with any other technology So, it really highlights the extraordinary capabilities of a high-power, direct-diode laser to bring the benets of cladding to the very large parts that are common in construction, oil and gas, mining, and other heavy industrial sectors ”

“But, APEX ETG’s laser cladding capabilities cater to applications of all sizes and geometries This enables us to service the needs of a wide range of industries within Western Australia It is thanks to our strong relationship with Coherent that we are able to bring this technology into the market ”