Hi Guys,
Hope to get your input on this issue.
For the past 1 year, on and off we are seeing some weird big oxides in the Metco 443 coating, which according to our observation, it usually occurred when the batch of powder contained around 3wt% or more of powder at -325mesh size. We feedback to Metco regarding this, which they simply said this issue was mainly due to turbulence and dust. But well, we do not really see this issue happen when the powder contained around 2wt% of -325mesh particle or less....so I am not sure what is the real cause.
We are using Metco 9MB gun, consoles are 9MC or Multicoat (we have 3 systems in total), powder feeder is 9MP.
Below is the parameter we use, unit for airflow is SCFH.
Ar = 90 SCFH, H2 = 28 SCFH, Carrier, N2 = 12 SCFH, current = 550A, Nozzle = GH, SOD = 5.5 inch, surface speed = ~200ft/min, step size = 4 mm.
Microstructure image link below:
https://ibb.co/TrLX2Qs
https://ibb.co/ZmtGK3N
Hope you guys are able to help me on this.
Thanks,
CS