Cr3C2 Coating by HVOF

[Simon Kim]

Dear sir,

I am a beginner in a thermal spray field, have serviced in a roll manufacturing company.
I got a question and wonder if anyone can help.
I am doing a job and need to find a way to work Cr3C2-20NiCr thermal spray with GTV K2 HVOF gun after grinding fluted roll.
The roll is hollow bar same as tube shape, out dia 320mm.
Flute's height is about 2.5 to 4.8mm, several kinds of small module teeth.

I cannot to seem to think of any way during thermal spray to prevent lamination in the coating layer on side wall and bottom of flutes.
There are little difference, lamination is located in middle of coating layer on the side wall.
And that is located between substrate and coating layer.
So coating layer is not dense.
Maybe there are much residual stress by rapid cooling both of layers in my guess.
But top of the flutes have adequate coating layer, HV0.2 1030-1100 level.

The coating condition is same as belows.
powder size : +30-10 micro m
oxygen flow : 910 lpm
kerosene : 22.5 lph
substrate preheating : around 30? (one pass by HVOF gun)
powder feed : 70g/min
pass : 5 pass
distance : 280mm
coating thickness : top- 50/60 micro m, side wall- 38/46 micro m, bottom- 121/131 micro m

I was wondering if anyone can give any comments or other suggestion.
However I am not sure of the working principle and need help cause I might have to build it.

Thanks a lot

Simon

kimsimon@empas.com

[Florin]

(02-25-2010 11:39 AM)Simon Kim Wrote:  Dear sir,

I am a beginner in a thermal spray field, have serviced in a roll manufacturing company.
I got a question and wonder if anyone can help.
I am doing a job and need to find a way to work Cr3C2-20NiCr thermal spray with GTV K2 HVOF gun after grinding fluted roll.
The roll is hollow bar same as tube shape, out dia 320mm.
Flute's height is about 2.5 to 4.8mm, several kinds of small module teeth.

I cannot to seem to think of any way during thermal spray to prevent lamination in the coating layer on side wall and bottom of flutes.
There are little difference, lamination is located in middle of coating layer on the side wall.
And that is located between substrate and coating layer.
So coating layer is not dense.
Maybe there are much residual stress by rapid cooling both of layers in my guess.
But top of the flutes have adequate coating layer, HV0.2 1030-1100 level.

The coating condition is same as belows.
powder size : +30-10 micro m
oxygen flow : 910 lpm
kerosene : 22.5 lph
substrate preheating : around 30? (one pass by HVOF gun)
powder feed : 70g/min
pass : 5 pass
distance : 280mm
coating thickness : top- 50/60 micro m, side wall- 38/46 micro m, bottom- 121/131 micro m

I was wondering if anyone can give any comments or other suggestion.
However I am not sure of the working principle and need help cause I might have to build it.

Thanks a lot

Simon

kimsimon@empas.com

Hello Simon


Can you attach a picture / microstructure or at least a little drawing of this problem? It would be intersting to see this. Do you inject 2x35g/min powder? There are several acceleration nozzles of K2 with different lengths and internal geometry. Which one do you use?

What is the commercial name of the powder used?


Best regards,
Florin

[Simon Kim]

Hello Florin,

Yes, our feeder is 2X35g/min.
And acceleration nozzle is same as gun barrel?
Barrel size is 6"(150mm) inner dia. 11mm.
Powder is WOKA 7104, Cr3C2 20NiCr, -30+10 micro m.

I would like to attach the pictures of coating layer, however I can not upload the file. I should try to send by other way.

regards

Simon

[Simon Kim]

Hi Florin,

I can not attach the picture files, I have knoe idea what can I do in web.
Attachments option is not work after click 'add attachment'.
And I tried to attach on this area by snap program, but it was not also.

How can I send the pictures?

Simon

[Florin]

(02-26-2010 07:20 AM)Simon Kim Wrote:  Hi Florin,

I can not attach the picture files, I have knoe idea what can I do in web.
Attachments option is not work after click 'add attachment'.
And I tried to attach on this area by snap program, but it was not also.

How can I send the pictures?

Simon

kimsimon@empas.com

Hello Simon

You should ask Gordon (site administrator) to help you put the picture on the site. Write him a message.

Regards,
Florin