Black Spots on TBC coating

[Aliebram]

Hi Friends,
I lost my old user and this is new. I have an issue by TBC. After spray there are small black spots on the coating. I am spraying by SG-100 and the parameters as the Praxair suggested.

Could you help me, what is the reason of these black spots (dots) on coating? I enclosed the images for your consideration. Your recommendation will help me a lot.

Regards,

[Vadim Verlotski]

Hi Friends,
I lost my old user and this is new. I have an issue by TBC. After spray there are small black spots on the coating. I am spraying by SG-100 and the parameters as the Praxair suggested.

Could you help me, what is the reason of these black spots (dots) on coating? I enclosed the images for your consideration. Your recommendation will help me a lot.

Regards,

For example, they can be impurities from the powder feeder or from powder tubing. If metal powder or Cr2O3 was previously sprayed with the plasma system, these powder residues can form black spots on white YSZ.

[Stephen Booth]

What powder brand are you using? Is the color normally white or yellow?

We have seen some tiny black spots coming from the powder in the past, especially when it was the white color coating?

[Aliebram]

Thanks for your comments, the problem solved.

thanks,

[J!m]

so.. Was it contamination from the bond coat?

Metco 204NS has had occasional black spots since the very first batch was produced. I was involved a few times over the years with "customer complaints", and it was *not* a contamination issue, neither in powder manufacturing, nor in spraying. It just happens.

A strong theory is that some of the yttria converts to yttrium in the plasma. Under XRD and EDS the "contamination" could not be identified as any element not in the original coating (204NS is a Yttria stabilized Zirconia).

[Taz]

so.. Was it contamination from the bond coat?

Metco 204NS has had occasional black spots since the very first batch was produced. I was involved a few times over the years with "customer complaints", and it was *not* a contamination issue, neither in powder manufacturing, nor in spraying. It just happens.

A strong theory is that some of the yttria converts to yttrium in the plasma. Under XRD and EDS the "contamination" could not be identified as any element not in the original coating (204NS is a Yttria stabilized Zirconia).

Hi Jim,

I'm interested in your information here. Are you saying that for METCO 204NS, it is normal to have a black spot on the coating?
Does it normally have a lot of black spot on the coating layer?

[J!m]

so.. Was it contamination from the bond coat?

Metco 204NS has had occasional black spots since the very first batch was produced. I was involved a few times over the years with "customer complaints", and it was *not* a contamination issue, neither in powder manufacturing, nor in spraying. It just happens.

A strong theory is that some of the yttria converts to yttrium in the plasma. Under XRD and EDS the "contamination" could not be identified as any element not in the original coating (204NS is a Yttria stabilized Zirconia).

Hi Jim,

I'm interested in your information here. Are you saying that for METCO 204NS, it is normal to have a black spot on the coating?
Does it normally have a lot of black spot on the coating layer?

It varies- lot to lot and day to day. Spraying hotter can help but the possibility is always there.

[Taz]

It varies- lot to lot and day to day. Spraying hotter can help but the possibility is always there.

I have issue with this coating which always high on the porosity.
And causing me wasting a lot of powder. What gun are you using to spray this powder?

[J!m]

It varies- lot to lot and day to day. Spraying hotter can help but the possibility is always there.

I have issue with this coating which always high on the porosity.
And causing me wasting a lot of powder. What gun are you using to spray this powder?

If your porosity is too high, you need to increase temperature, velocity or both.

I have successfully sprayed 204 to the usual (and some unusual) specs with the Metco guns (3m, 7m, 9m, 11m, 7mt Sinplex and Triplex) and the Swiss guns (f4, f100, f210, f300)

What spec are you going for and what gun are you using? With Argon primary, it can be difficult to get enough heat in the Metco guns. In a 3m, make sure your gas ring is in good shape and installed correctly. You may also try a 9m63 electrode in place of the 2m11 in the 3mb gun. But often a significant flow of hydrogen is needed.

Nitrogen/hydrogen is far more efficient with two diatomic gasses but it tends to really chew up the nozzle. In that case, a tungsten lined nozzle may make sense. They are quite expensive (about $125) but last a very long time with argon and also much better with n2/h2. They were developed in Germany for the electronics market where there is zero tolerance for copper spits.

[Taz]

If your porosity is too high, you need to increase temperature, velocity or both.

I have successfully sprayed 204 to the usual (and some unusual) specs with the Metco guns (3m, 7m, 9m, 11m, 7mt Sinplex and Triplex) and the Swiss guns (f4, f100, f210, f300)

What spec are you going for and what gun are you using? With Argon primary, it can be difficult to get enough heat in the Metco guns. In a 3m, make sure your gas ring is in good shape and installed correctly. You may also try a 9m63 electrode in place of the 2m11 in the 3mb gun. But often a significant flow of hydrogen is needed.

Nitrogen/hydrogen is far more efficient with two diatomic gasses but it tends to really chew up the nozzle. In that case, a tungsten lined nozzle may make sense. They are quite expensive (about $125) but last a very long time with argon and also much better with n2/h2. They were developed in Germany for the electronics market where there is zero tolerance for copper spits.

I'm currently using F4MB gun and my primary gas is Argon.
What distance did you used? mine is 140mm.

I'm actually thinking to increase my velocity on my next trial.
Hope it will improve though.

Do you also have experience with the bond coat Amdry 962?

[Aliebram]

so.. Was it contamination from the bond coat?

Metco 204NS has had occasional black spots since the very first batch was produced. I was involved a few times over the years with "customer complaints", and it was *not* a contamination issue, neither in powder manufacturing, nor in spraying. It just happens.

A strong theory is that some of the yttria converts to yttrium in the plasma. Under XRD and EDS the "contamination" could not be identified as any element not in the original coating (204NS is a Yttria stabilized Zirconia).

Hi,

it was issue on filter of the Hopper and change and cleaned. I hate Praxair Hopper, very bad design.

[loriolo]

Hi Aliebram
SG 100 torch was designed to have it best result with Argon/Helium gases, maybe you are using Argon/H2, and in this case is normal that the nozzle could release spots of copper, you must change gas mix or gun if this spots are a trouble for you