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HFW Industries Technical Talk, Episode 4: Electric/Twin-Wire Arc
47 Plays2 years ago
Welcome to the fourth episode of our technical talk series. Today we discuss another thermal spray process that we commonly use in the shop, electric arc (which can also be referred to by twin-wire arc).
EA is a process that HFW has performed for much of our 75 year history, and while there may be more "advanced" techniques that we use today, electric arc is still an important one to utilize.
In this episode, we discuss best use cases for EA, what we have had success doing in the past, and how our thermal spray technologies may be able to help solve your equipment problems.
If you have any questions about the electric arc process or would just like more information, please feel free to email jdwatson@hfwindustries.com.
Check out our social media for more awesome content and examples of electric arc at work. As always, thank you for listening!
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Transcript
Introduction to Electric Arc
00:00:09
Speaker
Okay. Welcome back to the HFW industries technical talk series. This is episode four. And today we will be discussing the electric arc process.
Overview of the Electric Arc Process
00:00:21
Speaker
I'm joined again by HFW's vice president, Matt Watson.
00:00:26
Speaker
And so Matt, I guess to dive right in, can we, can you discuss quickly, I guess just an overview of what the electric arc process is, and what it does and, and I guess kind of the origins and how we used it here at HFW. Okay, well electric arc or some people call it twin wire arc.
00:00:46
Speaker
is a process where we're using two wires are fed and when they intersect, they melt and form an electric arc. So that's the heat source. We have an electric arc that's melting the wires and then that molten material is propelled onto the substrate with compressed air.
History and Cost-Effectiveness of Electric Arc
00:01:10
Speaker
So, electric arc is when we look at kind of the spectrum of thermal spray process. Electric arc is one of the other ones, correct?
00:01:20
Speaker
Yeah, we've been using electric arcs here at HFW since I think the early to mid 70s is when we got our first electric arc unit. But we have several of these units, and it's got a niche. Just like plasma and HPOF, they all have their pros and cons. But I guess when we pick electric arc,
00:01:50
Speaker
here at HFW, a lot of times the two main reasons are when you get into large jobs and you're looking for general reclamation work, electric arc a lot of times wins out because of economics. It's a cheaper process than HVOF or plasma. So that's one advantage. And the other advantage is you're able to go
00:02:20
Speaker
pretty thick with
Applications and Advantages in Rebuilding
00:02:22
Speaker
these coatings. I mean, we, I can think of a number of instances where we have finished, you know, 80, a hundred thousandths thick. I remember one situation and not totally ideal. And we certainly told our customers, this was the last time we were doing this, but I remember we rebuilt a printing cylinder and we sprayed a 420 stainless coating, almost a quart of,
00:02:47
Speaker
quarter of an inch thick as sprayed. And we told them that that was starting to get to the limits, because there are limits with all thermal spray coatings. So it can be used just as a general, almost like an overlay, just rebuilding a part that's very worn down.
00:03:07
Speaker
Yeah, I mean, you know, we use it for rebuilding of shafts, printing cylinders, other rolls. You know, it's, it's a cheaper process because you're not using high volumes of gas like HVOF,
00:03:24
Speaker
or plasma, plasma is a more complex system. So you have expensive gun hardware. So there's no gas, there's no powder. I mean, these are wires. So powder, a 420 stainless wire right off the bed is a lot cheaper than a 420 stainless powder.
00:03:46
Speaker
So there's a cost savings there.
Electric Arc's Continued Relevance
00:03:49
Speaker
We're also able to spray electric arc. We're spraying at typically 25 to 30 pounds an hour. And so that's ideal for rebuilding. We've rebuilt shafts that are 10 inch diameter, 25 feet long. It's a lot quicker and cheaper to do electric arc.
00:04:13
Speaker
than with other processes, if that's the right solution. We always try and aim for what's best for the customer. So those are some of the advantages to the electric arc process.
00:04:29
Speaker
Yeah. So even though we have since we adopted electric arc, we have since added other processes, it seems like electric arc still has, there are still several good use cases for it. Correct. Correct. We, we use electric arc every, every day, just like we use plasma spraying and HVOF, um, spraying every day and they all have their advantages.
Materials and Applications
00:04:55
Speaker
Yeah. And again, I think this is where HFW as a company has really thrived over the years is being able to diagnose the best solution for a customer based on their needs and based on what they're trying to achieve with their equipment.
00:05:11
Speaker
So you talked about it tends to be a cheaper process or more economical process as compared to, uh, you know, HVOF or even plasma. Can you talk about some of the typical materials that might be applied? Um, and then maybe some typical applications or applications where electric arc tends to work well. Okay. Well, for us, we, you know, I would say with the electric arc process for us, the three main
00:05:38
Speaker
A couple of the main materials are 420 stainless, 316 stainless, Hastelloy C. For us, because of the markets that we're in, those are the most commonly sprayed materials with electric arc. Electric arc was developed to spray metals because you can make metals into wire form.
00:06:03
Speaker
So there are there have been over the years materials they've some of the manufacturers now have come out with what they called cord wires so you'll have a electrically conductive outer diameter.
00:06:18
Speaker
of a wire and inside it's kind of a tube structure inside they've started putting carbides inside and it's you know kind of a cheap cheap way to spray some other materials but predominantly what we're spraying here are you know metals and for us typical applications are
00:06:42
Speaker
printing rolls, various shafts, other processing rolls. The electric arc process also has
00:06:53
Speaker
you know, a little bit of a niche in that you can really, sometimes we'll have a customer, for example, in the printing industry, they sometimes will want us to coat a roll and leave it what we call as sprayed, meaning we're just leaving the roll as it was applied. We're not doing any subsequent grinding or machining of the coating.
00:07:16
Speaker
and they call out a specific texture. So they might call out, well, we want that roller, the face of the roller to be 500 to 600 RA. That's another niche of electric arc or traction coatings or anti-skid coatings because of the rough nature that can be easily applied.
Consultative Services and Expertise
00:07:42
Speaker
Because with the HVOF and plasma spraying, you're not, when you're spraying it as sprayed, you're not typically getting as rough of a surface. No, and it's HVOF is anywhere, and these are just general numbers, anywhere from maybe 175RA to 300RA, and then plasma spray would be
00:08:04
Speaker
Don't know. Let's call it. You know 250 RA to I don't know 400 some RA and and there's not you don't have the The ease to change the surface texture as you do with twin wire arc It's it's much easier to get a much rougher coating much consistent rate So, you know, that's
00:08:31
Speaker
Applying rough coatings is another niche or time when we'll use electric arc.
Innovations and Limitations of Electric Arc
00:08:38
Speaker
Well, I think all of this goes back to what we tend to be good at HFW is our ability to take what a customer is trying to get from their equipment or what they're trying to do in their process and figure out which process
00:08:55
Speaker
that we do here in which either when we're building apart new or rebuilding apart, course of action is best. And that comes from our years of experience. And we're able to work with the customer and truly offer more than just the straight up work. We can be that kind of like that consultation and give you that feedback based on what we've seen through doing this for over 70 years.
00:09:27
Speaker
So I think we've covered it pretty well. Is there anything else you'd like to note about the electric arc process that we should cover? No, I mean, just that it's a good process for depositing metallic coatings. As I said, there have been some newer advances where people have developed wires, kind of hollowed out wires where they put tungsten carbide or chrome carbide in there, but they're
00:09:54
Speaker
you know, covered with a metallic sheath, you know, those, those are some newer developments. Uh, you know, I guess the one disadvantage is, you know, with electric arc, you know, you can't spray, um, you can spray ceramics, you'd have to go plasma spray or the rock eyed process. And, and also carbides, as I said, people are putting tungsten in chrome carbides.
Episode Wrap-up and Contact Information
00:10:22
Speaker
They're using that in what they call metal cord wires, but those carbides from our work here, they're not as high a quality as HVOF. There are some advantages to electric arc, the cost, the throughput per hour that you're able to spray, but the main disadvantage is that you're really only able to use metals.
00:10:50
Speaker
Okay. I think in a 10 minute segment, that was a pretty comprehensive overview of electric arc. Of course, we are always happy to provide more information or talk with you specifically about a particular application. I will include some emails that you can contact if you have any more questions in the, in the notes to this podcast, but the time being, thanks for listening and we'll find you on the next episode.