Tungsten Carbide Microfinish

[engineerraj]

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

[LEN WOOD]

Hello Raju,

To achieve better than regular grinding (that is if you do have the coating quality/characteristics to support it) you'll have to 'Superfine'.

Are you working on Landing Gear coatings with Triumph Air Repair (AMTI)?

Cheers

GlenB

[Gordon]

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.

[djewell]

I have seen WC coatings finished better than 1 Ra using belt grinders. I only saw the finished product, so I can't say which belts were used to get the fine finish. I was under the impression that no special superfinishing techniques were used.

[pakalano]

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/

[sameer]

(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

[Gordon]

Hi sameer

to the Surface Engineering Forum.

Let us know how you get on

[karunanidhi]

what is the least roughness value can be obtained after lapping on WC-Co coating

[Gordon]

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.

[karunanidhi]

(07-14-2009 05:13 PM)Gordon Wrote:  Hi karunanidhi

Maybe a little under 1 Ra, but this will be highly dependent on coating quality/type and finishing technique.

Thanks gordon, 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.

[Gordon]

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

[raviswanadha]

Hi Sameer,
have a good sturdy machine something like G&P.
Girish

[karunanidhi]

(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