It would help if you could identify the hardware you spray with. Aluminum bronze ought to be easy to melt and spray.
Possibly, the powder carrier gas flow and powder injection port you're using, and maybe the nozzle, are not right for this powder with pure argon plasma gas, so the powder location and dwell time in the plasma jet aren't optimum. I would first consult with the equipment supplier to get a starting parameter recommendation.
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Robert Miller
Materials Engineering Consultant
R.A. Miller Materials Engineering
Indianapolis IN
(317) 698-5479
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Original Message:
Sent: 04-13-2021 11:06
From: Kristen Berube
Subject: Plasma Spray Gas Choice Problem
I currently spray an Aluminum Bronze powder using an Argon/Helium gas mixture. I have been experimenting with using only Argon but I am not able to get the same quality of coating. I have tried different parameters for the Argon that would give it equivalent properties to the mixture: equivalent enthalpy, mass flow rate, temperature, gun voltage, etc. No matter what I try, my microstructure is poor quality and my bond strength is low. There are really only two trends I've noticed in the microstructure. If I keep the Argon flow rate under 200 scfh I get many oxides and if it's over 200 scfh I get a good microstructure but I also get some separation at the interface. Both of these situations lead to the poor bond strength. To address the separation, I have tried improved surface prep, decreased spray distance, and more surface preheat, but none of that has worked.
So, my questions are:
- Has anyone else sprayed a similar metal powder using only Argon and what settings worked for you?
- Why does the addition of Helium create such a better coating? Why are my spray adjustments to account for its removal not adequate?
- Does anyone know of some additional strategies to address the separation at the interface?
Thank you,
Kristen
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Kristen Berube
Product Development Engineer
Turbocam
Dover NH
(603) 905-0461
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