How to determine the porosity level of Metco 320NS abradable coating?
08-09-2015, 01:04 PM, (This post was last modified: 08-10-2015, 02:52 PM by viewwer.)
#1
How to determine the porosity level of Metco 320NS abradable coating?
Dear All:
I have a problem when determine the porosity level of Metco 320NS coating.
What I have is the SEM image of coating section. The gray level of the porosity is very similar to the coating secondary filler hBN in the SEM image, so it is difficult to calculate the porosity level by ajusting the image.
Have anybody had similar problem, any help will be appreciate.
Reply
08-25-2015, 09:53 AM,
#2
RE: How to determine the porosity level of Metco 320NS abradable coating?
(08-09-2015, 01:04 PM)viewwer Wrote: Dear All:
I have a problem when determine the porosity level of Metco 320NS coating.
What I have is the SEM image of coating section. The gray level of the porosity is very similar to the coating secondary filler hBN in the SEM image, so it is difficult to calculate the porosity level by ajusting the image.
Have anybody had similar problem, any help will be appreciate.

Hello,
We measure porosity level in % using a microscope.
Usual % for top coat is of ~50%.
Microscope/Scan program measures % of darker spots wich represent porosity.
Cheers
Reply
10-01-2015, 03:50 AM,
#3
RE: How to determine the porosity level of Metco 320NS abradable coating?
Hi Viewwer,

Defining porosity is very tricky because what represents real porosity!
I have not seen any standard which tells you accurate what the level of porosity is for different materials.

Some standards even show you a figure and you can compare if your porosity match the one from the pictures, basically saying "we also don't know, should be something like this" :-)

That being said I can have a try for you analyzing your porosity with our analyzing software. If you send me a picture I will let you know what I think the porosity is and how I would interpret it, perhaps it will give you an idea of what to expect. Of course this is based on your preparation of the sample!

Just upload the picture to this forum. If w are luck we will have a fruitful constructive discussion wit other forum members.

regards,
Joris





(08-09-2015, 01:04 PM)viewwer Wrote: Dear All:
I have a problem when determine the porosity level of Metco 320NS coating.
What I have is the SEM image of coating section. The gray level of the porosity is very similar to the coating secondary filler hBN in the SEM image, so it is difficult to calculate the porosity level by ajusting the image.
Have anybody had similar problem, any help will be appreciate.

Reply
10-16-2015, 12:40 AM, (This post was last modified: 10-16-2015, 12:44 AM by Johnny_Blaze.)
#4
RE: How to determine the porosity level of Metco 320NS abradable coating?
(10-01-2015, 03:50 AM)Joris Kraak Wrote: Hi Viewwer,

Defining porosity is very tricky because what represents real porosity!
I have not seen any standard which tells you accurate what the level of porosity is for different materials.

Some standards even show you a figure and you can compare if your porosity match the one from the pictures, basically saying "we also don't know, should be something like this" :-)

That being said I can have a try for you analyzing your porosity with our analyzing software. If you send me a picture I will let you know what I think the porosity is and how I would interpret it, perhaps it will give you an idea of what to expect. Of course this is based on your preparation of the sample!

Just upload the picture to this forum. If w are luck we will have a fruitful constructive discussion wit other forum members.

regards,
Joris





(08-09-2015, 01:04 PM)viewwer Wrote: Dear All:
I have a problem when determine the porosity level of Metco 320NS coating.
What I have is the SEM image of coating section. The gray level of the porosity is very similar to the coating secondary filler hBN in the SEM image, so it is difficult to calculate the porosity level by ajusting the image.
Have anybody had similar problem, any help will be appreciate.

Hi Joris Kraak,

I don't see any image attachmenets.

I have a fair amount of experience with 320NS, but as you say, it is difficult to determine porosity. I don't have much experience in the lab, but, I have been told using a dye penetrate and vaccum impregnating the sample will help you see the porosity using a microscope equipped with a UV light.

Unfortunately due to the weak cohesive bonding, the hBN will also pull-out during polishing and give you a slightly higher porosity percentage.


Regards,
J.B.
Reply
10-18-2015, 04:20 PM,
#5
RE: How to determine the porosity level of Metco 320NS abradable coating?
HI Johnny,

The polishing is a matter of trial and error until you have a result which you think represents reality.

As you say impregnation with an epoxy and Fluorescent additive will definitely help you identify porosity. However what is porosity, would you indicate oxide strings as porosity? In the end they will also allow a certain permeability into the coating structure. The lower these oxide strings the higher the corrosion resistance. I tend to count oxide strings also as amount of porosity, or identify them separately in the analysis.

Reply
10-18-2015, 04:44 PM, (This post was last modified: 10-26-2015, 10:12 PM by Johnny_Blaze.)
#6
RE: How to determine the porosity level of Metco 320NS abradable coating?
(10-18-2015, 04:20 PM)Joris Kraak Wrote: HI Johnny,

The polishing is a matter of trial and error until you have a result which you think represents reality.

As you say impregnation with an epoxy and Fluorescent additive will definitely help you identify porosity. However what is porosity, would you indicate oxide strings as porosity? In the end they will also allow a certain permeability into the coating structure. The lower these oxide strings the higher the corrosion resistance. I tend to count oxide strings also as amount of porosity, or identify them separately in the analysis.

Hi Joris,
I guess I wouldn't identify the strings as porosity due to lack of experience in the lab, but doesn't the fluorescent additive help identify inter-splat separation? Sometimes the darker regions around the stringers can be mis-identified as stringers when they're possibly separations which the fluorescent additive can penetrate between the splat boundary of the strings no?

Regards,
John
Reply
11-23-2015, 09:57 AM,
#7
RE: How to determine the porosity level of Metco 320NS abradable coating?
Hi John,

Exactly, it helps identifying pores and non pores.

cheers,
joris



(10-18-2015, 04:44 PM)Johnny_Blaze Wrote:
(10-18-2015, 04:20 PM)Joris Kraak Wrote: HI Johnny,

The polishing is a matter of trial and error until you have a result which you think represents reality.

As you say impregnation with an epoxy and Fluorescent additive will definitely help you identify porosity. However what is porosity, would you indicate oxide strings as porosity? In the end they will also allow a certain permeability into the coating structure. The lower these oxide strings the higher the corrosion resistance. I tend to count oxide strings also as amount of porosity, or identify them separately in the analysis.

Hi Joris,
I guess I wouldn't identify the strings as porosity due to lack of experience in the lab, but doesn't the fluorescent additive help identify inter-splat separation? Sometimes the darker regions around the stringers can be mis-identified as stringers when they're possibly separations which the fluorescent additive can penetrate between the splat boundary of the strings no?

Regards,
John

Reply




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