Yellow Spot on Thermal Barrier Coating
10-15-2020, 09:13 AM,
#1
Yellow Spot on Thermal Barrier Coating
Hi friends

i have a issue to my thermal barrier coating for nozzle segment in GE gas turbine. after one day spray there are yellow spot on my coating. I am spraying with 7MC unit control and 3MB gun from Metco Sulzer, bond coat: AMDRY 962 and top coat: METCO 204 NSG

Could you help me, what is the reason of these yellow spots (dots) on coating?
From our experience inspector it is caused by uncleaned penetrant removal process, how about you guys??

I enclosed the images for your consideration. Your recommendation will help me a lot.
Thank you

Best
Achmad Arifudin H


Attached Files Thumbnail(s)
   
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10-15-2020, 01:13 PM,
#2
RE: Yellow Spot on Thermal Barrier Coating
Did you finish (polish) the coating or is that as sprayed? If you used a die grinder to finish the coating and it had oil in it (as is normal for lubrication), then it could have been exhausted onto the coating.
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10-15-2020, 04:49 PM, (This post was last modified: 10-15-2020, 04:51 PM by Lyokha ibn Ivanovich.)
#3
RE: Yellow Spot on Thermal Barrier Coating
I think the substrate is cast iron. And in its pores there are residues of hydrocarbons. Weakly annealed the surface. Sori might be wrong.
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10-15-2020, 07:35 PM, (This post was last modified: 10-15-2020, 07:37 PM by plasmajet1990.)
#4
RE: Yellow Spot on Thermal Barrier Coating
(10-15-2020, 09:13 AM)achmadarifudinh Wrote: Hi friends

i have a issue to my thermal barrier coating for nozzle segment in GE gas turbine. after one day spray there are yellow spot on my coating. I am spraying with 7MC unit control and 3MB gun from Metco Sulzer, bond coat: AMDRY 962 and top coat: METCO 204 NSG

Could you help me, what is the reason of these yellow spots (dots) on coating?
From our experience inspector it is caused by uncleaned penetrant removal process, how about you guys??

I enclosed the images for your consideration. Your recommendation will help me a lot.
Thank you

Best
Achmad Arifudin H
Hi,

Maybe the air used for cooling is polluted with oil.

Regards,
Ion
Reply
10-16-2020, 06:42 AM,
#5
RE: Yellow Spot on Thermal Barrier Coating
(10-15-2020, 07:35 PM)plasmajet1990 Wrote:
(10-15-2020, 09:13 AM)achmadarifudinh Wrote: Hi friends

i have a issue to my thermal barrier coating for nozzle segment in GE gas turbine. after one day spray there are yellow spot on my coating. I am spraying with 7MC unit control and 3MB gun from Metco Sulzer, bond coat: AMDRY 962 and top coat: METCO 204 NSG

Could you help me, what is the reason of these yellow spots (dots) on coating?
From our experience inspector it is caused by uncleaned penetrant removal process, how about you guys??

I enclosed the images for your consideration. Your recommendation will help me a lot.
Thank you
Hi,

Maybe the air used for cooling is polluted with oil.

Regards,
Ion
Hi Ion,

Did you meaning air cooling used while coating process??

best,
Achmad
Reply
10-16-2020, 06:45 AM,
#6
RE: Yellow Spot on Thermal Barrier Coating
(10-15-2020, 01:13 PM)Lemster68 Wrote: Did you finish (polish) the coating or is that as sprayed?  If you used a die grinder to finish the coating and it had oil in it (as is normal for lubrication), then it could have been exhausted onto the coating.

Hi lems

this is as sprayed.

and updated i try to polish the defect then i do re-coating TBC to make same color. And then this defect still occur.

Any suggest buddy??

Best
Achmad
Reply
10-16-2020, 05:46 PM, (This post was last modified: 10-16-2020, 05:51 PM by plasmajet1990.)
#7
RE: Yellow Spot on Thermal Barrier Coating
(10-16-2020, 06:42 AM)achmadarifudinh Wrote:
(10-15-2020, 07:35 PM)plasmajet1990 Wrote:
(10-15-2020, 09:13 AM)achmadarifudinh Wrote: Hi friends

i have a issue to my thermal barrier coating for nozzle segment in GE gas turbine. after one day spray there are yellow spot on my coating. I am spraying with 7MC unit control and 3MB gun from Metco Sulzer, bond coat: AMDRY 962 and top coat: METCO 204 NSG

Could you help me, what is the reason of these yellow spots (dots) on coating?
From our experience inspector it is caused by uncleaned penetrant removal process, how about you guys??

I enclosed the images for your consideration. Your recommendation will help me a lot.
Thank you
Hi,

Maybe the air used for cooling is polluted with oil.

Regards,
Ion
Hi Ion,

Did you meaning air cooling used while coating process??

best,
Achmad
Hi

Yes, the air for cooling used in process

Best regards,
Ion
Reply
11-21-2020, 01:45 PM,
#8
RE: Yellow Spot on Thermal Barrier Coating
Hi Achmad Arifudin H
Did you try to make a heat treatment after the Yellow Spot occur?
I have the same situation,at July,after a rainy day.
The coating is easy to adsorb the ash in wet air, because YSZ is porosity structure.It is OK, if the Yellow Spot is gone after the vane are heat-treated.
You can have a try!

Beat wishes.
Jackson Zhao.
Reply
11-25-2020, 09:07 AM,
#9
RE: Yellow Spot on Thermal Barrier Coating
(11-21-2020, 01:45 PM)Jackson Zhao Wrote: Hi Achmad Arifudin H
Did you try to make a heat treatment after the Yellow Spot occur?
I have the same situation,at July,after a rainy day.
The coating is easy to adsorb the ash in wet air, because YSZ is porosity structure.It is OK, if the Yellow Spot is gone after the vane are heat-treated.
You can have a try!

Beat wishes.
Jackson Zhao.

Hi Zhao

i already try it to air furnace with 85 celcius for 15 minutes but the yellow spot doesnt removed. So i polishing the yellow spot until is blur visually and re-touch up coat until the thickness requirement.
Maybe u can share how much temperature to removed yellow spots

Thanks,
Achmad Arifudin H
Reply
11-25-2020, 02:00 PM,
#10
RE: Yellow Spot on Thermal Barrier Coating
85c for that short a time you would be lucky to just dry it off if it were water.  Do you have an ageing treatment after the coating process?
Reply
11-30-2020, 06:23 AM,
#11
RE: Yellow Spot on Thermal Barrier Coating
(11-25-2020, 02:00 PM)Lemster68 Wrote: 85c for that short a time you would be lucky to just dry it off if it were water.  Do you have an ageing treatment after the coating process?

Hi lems

its just as sprayed, we dont get a heat treatment after coating. Is this common doing heat treatment after spray for TBC coating, as i know heat treatment performing just at MCrAlY HVOF for higher bonding strength and to get minimum porosity.

Thanks, Best
Achmad Arifudin H
Reply
11-30-2020, 05:32 PM,
#12
RE: Yellow Spot on Thermal Barrier Coating
Heat treatment ought to be determined by whether customer requirement/specification says it should or should not be done.
Reply




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