04-03-2009, 05:54 PM,
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engineerraj
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Tungsten Carbide Microfinish
Hi,
We are looking to gring an HVOF coating to a micro finish of 4 Ra. Does anyone have any suggestions? We have been able to get to 7 Ra but cannot seem to improve on it. We use a profilometer to measure.
Thanks
Raju
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04-07-2009, 03:51 PM,
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Gordon
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RE: Tungsten Carbide Microfinish
Hi Raju
 to the Surface Engineering Forum.
I agree with GlenB, you may need to use super-finishing techniques to get below 4 microinch Ra, though with the right grinding wheels and techniques, a good HVOF carbide coating should be capable of 2-4 microinch Ra finish.
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06-04-2009, 07:47 PM,
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pakalano
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RE: Tungsten Carbide Microfinish
We are presently obtaining 4Ra only grinding. Unfortunately it is not the most cost effective solution, so we have implemented a belt finishing technique to keep costs at a minimum. a superfinishing machine is roughly $12000.00USD and a tool post mount polisher using a slack belt is around $1100.00USD. We grind using a 220grit wheel and obtain around a 16Ra, then belt grind using a few different grits of diamond belts to obtain a 2Ra with no real effort. THe belts are realily available from 3M.
There is another product out there that is also an excellent choice for cylindrical grinding of carbides if your budget allows for it. Abbott Machine of Illinois manufactures retrofit kits for cylidrical grinders that allow you to obtain down to a 1Ra using belts only with very precise tolerances. Not cheap though. Check the link.
http://abbottmachineco.com/
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07-11-2009, 02:00 PM,
(This post was last modified: 07-11-2009, 02:04 PM by sameer.)
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sameer
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RE: Tungsten Carbide Microfinish
(04-03-2009, 05:54 PM)engineerraj Wrote: Hi,
We are looking to gring an HVOF coating to a micro finish of 4 Ra. Does anyone have any suggestions? We have been able to get to 7 Ra but cannot seem to improve on it. We use a profilometer to measure.
Thanks
Raju
dear raju,
today only i have registered , i was also looking for the same solution ,I found 3M Trizact Diamond cloth belts 663FC ,
I am going to try these belts,However I will design and fabricate belt polisher Myself,
sameer
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07-11-2009, 02:23 PM,
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Gordon
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RE: Tungsten Carbide Microfinish
Hi sameer
 to the Surface Engineering Forum.
Let us know how you get on
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07-14-2009, 05:13 PM,
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Gordon
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RE: Tungsten Carbide Microfinish
Hi karunanidhi
Maybe a little under 1 microinch Ra (0.025 micrometre) , but this will be highly dependent on coating quality/type and finishing technique.
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07-16-2009, 12:01 AM,
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Gordon
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RE: Tungsten Carbide Microfinish
Hi karunanidhi
Quote:We made a trial shaft sample of dia 50 mm, after grinding and lapping we have obtained a finish of 0.03 Ra. Will it be possible to achieve the same roughness value on a roll of dia 1500mm.
I don't see why not, if you use same methods.
I assume 0.03 Ra is in micrometers and not microinches?
I think we are all guilty of expressing Ra values without indicating the measurement unit. Big difference between Ra in microinch and micrometre. I will edit my previous post just in case of confusion
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07-17-2009, 12:52 PM,
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karunanidhi
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RE: Tungsten Carbide Microfinish
(07-16-2009, 12:01 AM)Gordon Wrote: Hi karunanidhi
Quote:We made a trial shaft sample of dia 50 mm, after grinding and lapping we have obtained a finish of 0.03 Ra. Will it be possible to achieve the same roughness value on a roll of dia 1500mm.
I don't see why not, if you use same methods.
I assume 0.03 Ra is in micrometers and not microinches?
I think we are all guilty of expressing Ra values without indicating the measurement unit. Big difference between Ra in microinch and micrometre. I will edit my previous post just in case of confusion  you are true gordon, the units of my earlier mail is in micrometers. as far of my knowledge the database on grinding and finishing of thermal spray coatings is still in dark side . we the technocrats of this esteemed technology should bring the facts into light. i request all of us should exchange and explore the knowledge of post coating treaments like grinding, sealing operations.
any useful informative web sites may suggest
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11-11-2022, 01:49 PM,
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SakshiVerma
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RE: Tungsten Carbide Microfinish
It is possible to bring an HVOF coating to a micro finish, but there may be better options for your application. Grinding can cause damage to the film and reduce its performance capability. You may need more coatings than if you had applied the HVOF directly to the substrate. When choosing a grinder, ensure it has adequate grinding capabilities and that its wheel system is robust enough to handle high volumes of material without breaking down or becoming clogged up. Another alternative would be sandblasting followed by clear-coating with an HVOE coating using a sprayer attachment for maximum coverage and protection against wear and tear.
Design Engineer at Testo India
Manufacturer Of Portable Combustion Efficiency Analyzers
https://www.testo.com/en-IN/
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02-17-2023, 09:41 PM,
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J!m
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RE: Tungsten Carbide Microfinish
I have done it. HVOF WC can be brought to under 4 microinch Ra easily with a 400-grit diamond wheel (properly dressed and trued/balanced) and then run the last .0004" or so and spark-out passes using a filter on the coolant line. With a 320 wheel, your particulate in the coolant stream is (up to) 320 mesh, so you will have a very hard time getting better as-ground finish than that.
By filtering the "abrasive" out of the coolant, you can greatly improve surface finish.
Prior to this we were using a Supfina as a second operation to get 1-2 microinch Ra (quite easily), and after adding the filter, we could hit that with no secondary operations.
Since we sprayed the parts right next door, we could tailor the overage at spray, to minimize both spray time as well as grind time taking it back off. Then the elimination of the secondary operation (and thereby compressing processing time door-to-door) was like doubling the price of the parts, but always early... everyone wins.
Spraying since '87. University of Metco alum (99-16)
Available for consultation services- please send a PM
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