yttria stabilized zirconia (TBC) Porosity issue

[cris1904]

Hello All, I am looking for a polishing procedure that will work for yttria stabilized zirconia (7YSZ)with a bond coat of NiCrAlY.

I currently grind until planar up to 1200P SiC paper then 15min on a napless pad (PanW or Dac) @150rpm and 4 mounts/20nwts per mount with .05 colloidal silica dosing. The problem is I don't get consistent results, I is too much "pull out".
I have tried both short times and longer times with the longer giving better results. I'm just hoping that there is someone that deals with this coating on a regular basis in their lab and could point me in the right direction. I have searched the archives many times before posting this thread and couldn't find any info on proper polishing techniques. I find that there is minimal "pullout" on both ends of the sample and near the interface. I tried to post some pics but having a little trouble.

Thank you,

Cris.

[texnicar]

Hi Cris,

I have parameters for grinding yttria stabilized zirconia (TBC), if they will help you I can send it to you.

[cris1904]

Texnicar, that would be great. Thank you

[texnicar]

I hope that you can read data from picture.

Can you tell me which masking tape did you use?

[cris1904]

Texnicar, thank you for the info, but I was looking for a polishing procedure for the TBC coating.
I was able to find a procedure from Sulzer, which works great!!

Thank you,

Cris

P.S. If someone ever needs it, I would be happy to share it or a procedure for HVOF or Plasma coatings (Cu-Ni-In, Al-Bronze, Ni-Al, WC-Co, ect) I have those as well.

[Joris Kraak]

Hi Cris,

It is indeed very complicated to reduce the amount of pullouts and get consistent results. Let me discuss briefly what works for me!


1. send samples to different abs to get reference, you will be surprised of different results :-)
2. use a cutting disc (diamond) as thin as possible.
3. always use cold epoxy mounting technique with vacuum in order to fill pores.
4. plane grinding with 600 (new disc approximately 2 minutes is enough) low RPM 100 same rotation 20, pressure 1.0
5. grinding 1200 (new disc 2 minutes is enough) RPM 100 same rotation 20, pressure 1.0

At this stage the cutting scars are removed (check under microscope)

6. polish 3 microns (10 minutes)
7. polish 1 microns (10 minutes)

I haven't got any written procedures yet but that is in the pipeline, once I got it will send it to you!

regards,
Joris