sealer for sink roll coating

[karunanidhi]

Hello all,

I appreciate&thank all the members of surface engineering forum especially gordon for the best knowledge tranfer among thermal spray community which is not happening in other upcoming technological branches. On the same intrest here i request you all to provide available information on the following.

we had a query of coating steel industry rolls from one of the leading steel manufacturer in India. do you have any coating knowledge about these rolls(like briddle rolls , sink rolls, deflector rolls, web rolls etc). In my study, i found that there is a requirement of special sealant after coating. I wish to request your expertise in this niche area for the following

1. is the sealant required for all steel industry rolls or it is required only for the rolls used in the bath line?

2. What is the sealant material and its application process?

3. what kind of sealant used for sink rolls?

4. any useful study material available for the surface properties of steel industry rolls?

an early response is highly solicited


regards
karunanidhi.

[Intel55]

Loctite 290 or Metcoseal ERS.
This was used on a double eagle HD roll that was in a galvanizing line for metal sheets. Part of the shaft was in 13% HCl. 86/10/4 wc/co/cr.

Clean surface with Acetone

- Grit blast object (make sure pressure is not too high or you will blast AL2O3 into the part)

- Do not clean with brush

- Blow the dust of the substrate with dry and oil free air.

- Make sure RPM is high (depending on substrate Diameter)

- Make sure traverse speed is high

- Spray with the correct parameters

- Keep temperature of the substrate below the 120*C

- After coating apply Loctite 290 sealer (temperature of substrate below 70*C)

- Grind the coating

- Seal the coating again

[karunanidhi]

Dear Intel,

Thank youfor your valuable inputs.


regards
karunanidhi

[adam wintle]

I was under the impression that the sink rollers were HVOF sprayed with 88/12 WC/co then a chromic acid sealer was applied and baked. I also know that some people tried a WC/WB/co coating for baths containing small percentages of aluminium.

[karunanidhi]

Dear Adam,

with reference to my study, your answer seems to be appropriate for sink roll solution

but the first solution given by Mr. INTEL might be suitable for some other roll used in hot bath line.could you please explain the process in detail.

regards
karunanidhi

[drramc]

In India,thermal spray coatings of Sink Rolls had more failures than sucess, inspite of using the right material and process.The reasons are too numerous to describe here, but mostly due to lack of knowledge in the basics of thermal spraying and the application.
R.Chattopadhyay

[Stephen Booth]

Considering the working conditions, loose fitting tolerances, heavy loading, temperatures, I would not consider using any thermal spray process for the Sink Rolls. Deloro Stellite of Koblenz makes Bushing for the sink rolls of solid stellite materials, or you could even weld the sink rolls with stellite or similar.

Why take the risk on such a critical application.

[karunanidhi]

(10-23-2008 12:55 PM)drramc Wrote:  In India,thermal spray coatings of Sink Rolls had more failures than sucess, inspite of using the right material and process.The reasons are too numerous to describe here, but mostly due to lack of knowledge in the basics of thermal spraying and the application.
R.Chattopadhyay

Dear Mr. Chattopadhyay

I agree with your comment, But the technological scenario in india is changing rapidly for the last 3-4 years. Earlier thermal spray workshops are been run by workshop supervisors with their past working knowledge without much educational background. But now Themal spray became a Blistering technology for researchers as well as Mechanical and metallurgical engineers in India.

So, my intention of the above long description is , What is the differentiating thing of us from the rest of the world. I believe that IF our effort is sincere and proceeded with right approach there is no barricade for sucess. India is not at all going to be lag behind in any of the technological innovations. One day we have to do it.

and i appreciate your sincere support for the above effort.

with regards
karunanidhi.

---

(10-24-2008 01:53 AM)Stephen Booth Wrote:  Considering the working conditions, loose fitting tolerances, heavy loading, temperatures, I would not consider using any thermal spray process for the Sink Rolls. Deloro Stellite of Koblenz makes Bushing for the sink rolls of solid stellite materials, or you could even weld the sink rolls with stellite or similar.

Why take the risk on such a critical application.

Dear Mr. Stephen,

I dont think of coating sink rolls as a risk. Because, sink rolls are being coated for a long years and are using successively in steel industries.
we had proper materials for all the surface charecteristics. and quality also can be maintained as desired.

Could you give some more details of your current process.


regards
karunanidhi

[Stephen Booth]

Dear Mr. Karunandhi:

Presently we do not repair Sink Rolls, and have a preference to sell the Ready Made Casting from Deloro Stellite or Weld with PTAW process with the filler of Stellite 6.

regards,

S Booth
Indonesia

[drramc]

Hi,
PTA stelliting would be probably be a good alternative but would be far too expensive compared to thermal spray process.A basic problem with cobalt is its solubility in zinc.Please check on this point before using Stellite6.
Therma spray process using WC-Co is a standard practice.and it's success depends on the expertise avialable. Altennative techno-economically viable,safe processes are also avialable to day.
ram chattopadhyay

[karunanidhi]

I found in some technical literature, that WC-12Co should be sealed by diffusion of alluminium.

[rayudugirish]

Hi Karuna,
For sealing you can use basically two techniques :
1 Polymer sealer like loctite or any other high temperature sealer will do.
alternately you can do one more thing
2 Apply a flash coat of NiCrBSi using plasma or HVOF. Results are good with plasma. Because after grinding you will not observe any visible porosity and Si will become SiO2 giving glassy finish. And the fluxing nature of the coating will penetrate into the pores. It works fine.

I believe liquid Zn will not dilute any of the coatings as well resist hot corrosion too.

As for as tolerances are concerned we have produced shafts in +- 2 microns.
Girish

[karunanidhi]

(10-31-2008 06:14 PM)rayudugirish Wrote:  Hi Karuna,
For sealing you can use basically two techniques :
1 Polymer sealer like loctite or any other high temperature sealer will do.
alternately you can do one more thing
2 Apply a flash coat of NiCrBSi using plasma or HVOF. Results are good with plasma. Because after grinding you will not observe any visible porosity and Si will become SiO2 giving glassy finish. And the fluxing nature of the coating will penetrate into the pores. It works fine.

I believe liquid Zn will not dilute any of the coatings as well resist hot corrosion too.

As for as tolerances are concerned we have produced shafts in +- 2 microns.
Girish

Dear Girish,


Thank you for your reply.

With refence to your reply at point 1. Loctite can never fulfill the requirements of sinks roll working environemnt

2. NiCrBsi may control the porosity but it will also differ with the working environment.

the main problems of the above case is thermal shock & dross pickup, so the coating applied on the roll should withstand for the above two charecteristics as well as satisfying the said requirements like porosity and Co-eff of thermal expansion with the bond coat.
Currently we are working on the above case in our R& D, Results reached almost required values. We will reveal the results very soon.


thanks& regards
karunanidhi

[Bala Kailasshankar]

There is a nano ceramic coating sealer available to close the pores. The life improvement is 2 to 3 times of unsealed carbide coated rolls.

[Gordon]

Hi Bala Kailasshankar

to the Surface Engineering Forum.

More information on this product would be welcome.

[djewell]

When spraying 88WC-12Co, make sure you get a low carbon content version (4%). We tried coating a roll with 5% C, and the results were not good.

[karunanidhi]

(02-11-2009 09:40 PM)Bala Kailasshankar Wrote:  There is a nano ceramic coating sealer available to close the pores. The life improvement is 2 to 3 times of unsealed carbide coated rolls.

Dear Mr. Bala kailasshankar,

may i know the nano material & tests that you have performed on the samples. By which process you have applied the coating.

[dadasotare]

(02-11-2009 09:40 PM)Bala Kailasshankar Wrote:  There is a nano ceramic coating sealer available to close the pores. The life improvement is 2 to 3 times of unsealed carbide coated rolls.

Dear Mr. Bala,

How to be apply this nano ceramic coating saler. Wether it bymanually or by .........Pl. describe.