HVAF development
12-06-2007, 12:31 AM,
#1
HVAF development
Dear Members,

I want to know more about the development of HVAF worldwide.

Since HVAF sprays excellent WC-Coating, what's the reason that its application is so limited?
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12-06-2007, 05:10 PM,
#2
RE: HVAF development
Hi ycwbycwb

Quote:I want to know more about the development of HVAF worldwide.
Try Google search term ""high velocity air fuel"" in preference to "hvaf"

For those that would like to see YouTube video clip of HVAF in action
Thermal Spray HVAF

Quote:Since HVAF sprays excellent WC-Coating, what's the reason that its application is so limited?
While HVAF process in principle has been around for a while, its development and commercialisation has been slower than HVOF up to now. I think the future for HVAF along with CGDS (cold gas dynamic spray) or cold spray is bright. Note the development over the years in thermal spray, with the emphasis on thermal moving towards kinetic. The newer technologies will not necessarily displace the older technologies as they all have their pros and cons, but it will certainly expand the overall capability.
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01-05-2008, 06:01 PM,
#3
RE: HVAF development
Hi, ycwbycwb, as far as I know the selling point of HVAF is cost saving, as it does not use Oxygen, however, I got to prepare a high capacity 380v electrical power for this machine as it needs a big air compressor. You know we only use such high power for APS. This limits its cost advantage. Also, it needs extra fine powder for better melting.
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01-06-2008, 05:06 PM,
#4
RE: HVAF development
Dear All,
I would also like to know about the componies who sell HVAF equipments
Regards
Vijay Deshpande
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01-06-2008, 05:44 PM,
#5
RE: HVAF development
Hi Vijay

Try Google search term ""high velocity air fuel"" in preference to "hvaf"
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01-07-2008, 09:13 AM,
#6
RE: HVAF development
I only know the following two:
Kermetico
Uniquecoat

Actually these two are one company before 2006. Then for some reason the founders separated apart. The technology is based on the same patent. Spraying coatings with the equipment can be seen at youtube, one has been posted by Gordon, I add another):

https://www.youtube.com/watch?v=FglI2CfZxV4
https://www.youtube.com/watch?v=HQAdQvDrSl0

Large paper machinery company Metso has been using this equipment to spray WC coating onto large paper rolls.
Good things:
1. No pure oxygen source is needed.
2. Longer spare parts service time.
3. Better WC coating performance confirmed by many reports(wear, toughness, fatigue)

Bad things:
1. Large air compressor: at least 10m3 per min. (but don't forget large cooling need for many HVOF)
2. Manufactures are small companies.
3. Fine powders, -30+5 microns WC, for better DE, 45%. ( However Kermetico claims to add little H2 to the powder feeder gas, so fine powders has DE over 60% and coarse powder for HVOF has DE over 40%)
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01-07-2008, 01:06 PM,
#7
RE: HVAF development
Good post by ycwbycwb Cheers

I would only add to the list of good things
Quote:1. No pure oxygen source is needed.
2. Longer spare parts service time.
3. Better WC coating performance confirmed by many reports(wear, toughness, fatigue)
4. Air cooled, no water cooling plant required (off-set a little by extra compressed air needed as mention before).
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01-07-2008, 04:53 PM, (This post was last modified: 08-05-2008, 01:45 PM by plasmajet1990.)
#8
RE: HVAF development
Hi,

Try at this address:


Ion Trusca
https://www.plasmajet.ro
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01-08-2008, 04:45 AM,
#9
RE: HVAF development
Ion trusca seems to purchase HVAF-Arc equipment from UniqueCoat.

Thanks Gordon. I actually want to say the same as Gordon but my poor English.... Smile

Actually from the videos from Youtube you can spray WC coating with HVAF without additional cooling jets.
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01-08-2008, 10:50 AM,
#10
RE: HVAF development
Thanks alot for the info
Vijay Deshpande
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01-08-2008, 02:04 PM,
#11
RE: HVAF development
ycwbycwb Wrote:Ion trusca seems to purchase HVAF-Arc equipment from UniqueCoat.

Thanks Gordon. I actually want to say the same as Gordon but my poor English.... Smile

Actually from the videos from Youtube you can spray WC coating with HVAF without additional cooling jets.

Yes Plasma Jet has a HVAF-Arc and a Quasar equipments from UniqueCoat

Plasma Jet
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01-08-2008, 03:10 PM,
#12
RE: HVAF development
I would like to correct something from an earlier post. HVAF equipment only uses 5m^3/min of air, not 10. This is achieved easily with a 75 kW (100 Hp) compressor, which can be purchased very inexpensively. Our experience is it costs ~15 USD/hr to run the compressor when spraying with HVAF. Compare this to ~100 USD for liquid oxygen for an HVOF gun, and the economics favor HVAF. Additionally, the HVAF produces better quality coatings, is 5-10 times more productive (sprays faster), and consumes almost no spare parts.
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01-08-2008, 03:28 PM, (This post was last modified: 02-19-2009, 10:53 PM by djewell.)
#13
RE: HVAF development
ycwbycwb Wrote:Good things:
1. No pure oxygen source is needed.
2. Longer spare parts service time.
3. Better WC coating performance confirmed by many reports(wear, toughness, fatigue)

Bad things:
1. Large air compressor: at least 10m3 per min. (but don't forget large cooling need for many HVOF)
2. Manufactures are small companies.
3. Fine powders, -30+5 microns WC, for better DE, 45%. ( However Kermetico claims to add little H2 to the powder feeder gas, so fine powders has DE over 60% and coarse powder for HVOF has DE over 40%)

Solid Spray (the new company formed by the inventor of AC-HVAF technology and former director of UniqueCoat Technologies) has developed a new design for their gun to get up to 60% DE without the addition of H2 into the carrier gas stream. H2 addition with the new design will increase the DE further. Metal coatings sprayed with this design get DE's over 80% in many cases.
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01-08-2008, 05:33 PM,
#14
RE: HVAF development
Hi djewell

Thank you for the valued in-put into this discussion.

Sign0013 arguementative hat on Big Grin
Quote:Additionally, the HVAF produces better quality coatings, is 5-10 times more productive (sprays faster)
Surely this is for specific powder/coating types and not generic.

Quote:Solid Spray (formerly UniqueCoat Technologies) has developed a new design for their gun to get up to 60% DE without the addition of H2 into the carrier gas stream. H2 addition with the new design will increase the DE further. Metal coatings sprayed with this design get DE's over 80% in many cases.
Deposit efficiency is very reliant on the specific powder/parameters used. Example; HVOF spray trial of different powder supplies of essentially the same composition and particle size range, gave deposit efficiency values ranging from the worst at 35% to the best at 80%. Can't help thinking generic statements of deposit efficiency can be a bit misleading.

Please don't take this the wrong way as I believe HVAF is capable of producing higher quality coatings at more productive rates and more economically than HVOF for specific powder/coating types.

Cheers
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01-08-2008, 11:49 PM,
#15
RE: HVAF development
plasmajet1990 Wrote:
ycwbycwb Wrote:Ion trusca seems to purchase HVAF-Arc equipment from UniqueCoat.

Thanks Gordon. I actually want to say the same as Gordon but my poor English.... Smile

Actually from the videos from Youtube you can spray WC coating with HVAF without additional cooling jets.

Yes Plasma Jet has a HVAF-Arc and a Quasar equipments from UniqueCoat

Plasma Jet

Hi, Plasma Jet,
How about your Quasar equipments working? Is it really capable spraying 5-30 microns WC with higher DE?

BTW,
As I know, about 7m3/min air is consumed by SB9500 gun of Uniquecoat and about 5m3/min for SB9300, Kermetico gun and TSR3000 gun. I don't think 5m3/min capacity air compressor will be OK. I am not sure but you can check it with the manufacturers.
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08-31-2011, 06:18 PM,
#16
RE: HVAF development
ycwbycwb,

Sorry for the late reply, I just joined today. Having a background of traditional thermal spray, plasma, HVOF, arc etc. the differences between HVOF and HVAF are huge, as I have come to find now that I am involved in HVAF.

Everything said here is accurate, however all HVAF is not created equal even if they may have had the same starting point. We have made significant improvements to our AK-07 gun and system. We spray any metallic coating and cermets, no ceramics as there is insufficient heat to get the ceramics to a plastic point.

Here's what I have observed. HVAF is very parameter insensitive, we regularly change spray rate on the fly to even up coating thickness on long shafts or rolls. Spray rates are through the roof, we spray WC at up to 50 Lbs./Hr. and build it up at up to 0.002" per pass. We have sprayed it 0.50" thick, and gave up trying to find a thickness limitation. And after all that you can finish the coating to 0.4 Ra micro-inches. And all of this at at DE of 60% or so.

High spray rates, high DE's and high deposit per pass are typical of all coatings sprayed with our HVAF system. We check coating porosity with a gas permeability tester of our own design and find that WC is impermeably after about 0.004" of buildup. We are applying WC coatings in applications that had previously only been successful with D-gun carbide coatings. (sink rolls, and next month we spray a set of furnace rolls with CrC for a trial.)

The reason for all of these differences is that the feedstock material is not melted, just heated to near its melting point, then accelerated to extremely high velocities. I hesitate to post the number as I am afraid that people with industry experience would think I am pulling numbers from the air. Since the feedstock is not melted, dissolved o2 is negligible, we don't make any W2C by burning off carbon and oxidation is minimal.

We hit the concrete floor while spraying Hasteloy C-276 and the spray stream drilled a hole in the concrete. The back-plane of our spray cells collect the spray from the gun start/stop position where the gun is parked for start up and shut down. The coating builds up and forms what I call a 'walltite", a pointed conical metal slug. On any walltite I have seen from any other process it is a crumbly friable mess. The walltites that we make are solid metal and can be polished to a mirror finish and the back-plane of our booth is between 3' - 4' from the end of the nozzle! And to top it all off hardware life is extraordinary.

Given all of the differences between HVOF and HVAF, HVAF is the way to go for economy, and job throughput. The coat of our system is below 100K which also makes it attractive from a capital expenditure perspective.

I hope this helps. If you want to know more visit our website

Good luck,
JJStick
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11-09-2011, 10:23 PM,
#17
RE: HVAF development
JJStick,
You say that you have made "significant improvements" to your AK-07 gun and system. I'm wondering what these are?
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11-09-2011, 10:53 PM,
#18
RE: HVAF development
(11-09-2011, 10:23 PM)jasonpbond Wrote: JJStick,
You say that you have made "significant improvements" to your AK-07 gun and system. I'm wondering what these are?

Hello jasonpbond,

We have made modifications to the air circuit in the gun, this results in a higher chamber pressure which results in higher particle exit velocities.

We have optimized nozzle geometries, again with the goal of higher particle velocities.

We have made improvements in the ceramic element extending its life.

We have designed a hand held version of our AK-07 designated AK-06.

These are the main changes and apparently they have done some good.

Recently we have submitted samples of our 86-10-4 WC coating to a number of big names in the oil business. The comments we got back were all along the lines of "This is the best WC coating I have ever seen". One contact even added "by a large margin"

The bottom line is that the results are in the coating, and with 20+ years experience in thermal spraying I have never seen results such as we are getting with our HVAF system achieved by any other process.

For example our version of 86-10-4 is impermeable to the passage of gas or liquid with a coating thickness of only 50 microns or slightly less than 0.002". Before these changes the coating needed to more like 100 microns to guarantee impermeability . Further we can now achieve this level of coating density over a wide range of spray distances.

If hope this helps. If you need anything else just let me know.

Best regards,
JJStick

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01-30-2015, 05:13 PM, (This post was last modified: 01-30-2015, 05:20 PM by rofon.)
#19
RE: HVAF development
Hi JJstick,
I am currently looking for a HVAF equipment, and I've look the AK-07. Is the spark plug uses to ignite the AK-07?

Further more I'm asking my self what is the advantage of the HVAF compare to a D-gun?

Thanks !
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01-30-2015, 06:27 PM,
#20
RE: HVAF development
(01-30-2015, 05:13 PM)rofon Wrote: Hi JJstick,
I am currently looking for a HVAF equipment, and I've look the AK-07. It does look more like a D-gun than a HVAF! The spark plug make all the difference, is you AK-07 produces a continuous spray or it got a Hertz associate with it?

Further more I'm asking my self what is the advantage of the HVAF compare to a D-gun?

Thanks !

Hi Rofon,

Good questions, the spark plug is only for initial ignition, once the ceramic elements heats to past the auto-ignition temperature of the air/gas mixture combustion is continuous.

The main difference between Kermetico's HVAF process and any oxy-fuel combustion system is that we have a lower temperature of combustion, low enough that we can prevent the melting of the feedstock material. By not melting the feedstock we don't dissolve oxygen into the metal matrix which makes the coating brittle as solid particles absorb oxygen at a rate 1,000 times less than liquid particles.

Further we run fuel rich and have virtually no 'left over' oxygen to oxidize the outside of the particles, which creates a metal to metal bond between the particles in the coating structure. This results in high inter-particle cohesion. Our bond strength is also off the charts, the only result we get on an ASTM C633 bond test is broken glue at 12 KSI. And we get this result with carbides regardless if we blast the slug or not.

Our coatings even tungsten carbide are impermeable. We test impermeability with 300 PSI nitrogen and it only takes 50 microns of coating to be gas tight. We have a 0.0025" WC coating finished to an 8 Ra micro-inches running on a seal surface that sees 5,000 PSI of sea water with no sealer.

I realize that these claims sound outrageous and I would like the opportunity to substantiate them. I have a collection of documents, brochures, third party reports and metallography that is not on our website that I could send you via regular email. My contact info is on our website on the homepage at the bottom, my first name is John. Send me an email with your contact info and I'll send along those data.

Depending on your intended application the AK-07 may not be the best choice, so if you care to share your application details I can point you in the right direction regarding gun choice as we have a broad selection in our equipment portfolio.

Best regards,
JJStick




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