Separation of T400 Coating

[bepsi]

Trying to qualify T400 & T800 coatings.

Hello Forum Member,

I just started as a plasma coating engineer, and still very new to this area.

We were trying to qualify T400 & T800 coating at the same time. While T800 smoothly went through, T400 kept failing due to excessive separation between Inco718 substrate and the coating.

Our equipment supplier told us that these 2 coatings could be sprayed with the same parameter, which we did in the first place. Turned out the parameter worked well for T800, but not suitable to T400. We did try to lower down the Temperature by decreasing the Power and the amount of Hydrogen, still the problem stayed.

Since we applied the same Grit Blasting parameter to both coating, I don't think it's a problem of surface preparation. We're a little hesitant about the next step right now, how about lowering down the Powder Feed Rate? Anyone has any suggestion?

And I am really curious, how could 2 powders with similar composition possess such different characteristics?

[kschewe]

Hello Forum Member,

I just started as a plasma coating engineer, and still very new to this area.

We were trying to qualify T400 & T800 coating at the same time. While T800 smoothly went through, T400 kept failing due to excessive separation between Inco718 substrate and the coating.

Our equipment supplier told us that these 2 coatings could be sprayed with the same parameter, which we did in the first place. Turned out the parameter worked well for T800, but not suitable to T400. We did try to lower down the Temperature by decreasing the Power and the amount of Hydrogen, still the problem stayed.

Since we applied the same Grit Blasting parameter to both coating, I don't think it's a problem of surface preparation. We're a little hesitant about the next step right now, how about lowering down the Powder Feed Rate? Anyone has any suggestion?

And I am really curious, how could 2 powders with similar composition possess such different characteristics?

How thick are you spraying the coating. It has a limitation.

[jaybob1999]

We use the same parameters for both with great results.

[bepsi]

Hello Forum Member,

I just started as a plasma coating engineer, and still very new to this area.

We were trying to qualify T400 & T800 coating at the same time. While T800 smoothly went through, T400 kept failing due to excessive separation between Inco718 substrate and the coating.

Our equipment supplier told us that these 2 coatings could be sprayed with the same parameter, which we did in the first place. Turned out the parameter worked well for T800, but not suitable to T400. We did try to lower down the Temperature by decreasing the Power and the amount of Hydrogen, still the problem stayed.

Since we applied the same Grit Blasting parameter to both coating, I don't think it's a problem of surface preparation. We're a little hesitant about the next step right now, how about lowering down the Powder Feed Rate? Anyone has any suggestion?

And I am really curious, how could 2 powders with similar composition possess such different characteristics?

How thick are you spraying the coating. It has a limitation.

Thank you for the question. Our target thickness is 0.23-0.33mm, namely 0.009-0.012 inch.

[kschewe]

try adding dwell time. do not heat the substrate over 300. are you spraying over 5lb/hr? Can you use a bond coat of .002"?

[bepsi]

try adding dwell time. do not heat the substrate over 300. are you spraying over 5lb/hr? Can you use a bond coat of .002"?

Hello kschewe,

Sorry for the late response. The sample temperature was well below 130°C if that's what you meant. Our powder feed rate was actually 100g/min, namely 13.2 lb/hr. I am currently planning to lower down the feed rate.

As for the bond coat, our blueprint did not call for one, so applying bond coat shall not be an option. But thanks for sharing the ideas.

[kschewe]

That is a high feed rate for t400. 4-5lb/hr will help.