Cracking issues with plasma sprayed Wc-Co coating
Hello everyone!
I am currently trying to figure out the significant cracking issues on parts. We spray Metco 71vfns-1 to meet the PWA 257-1 coating spec. Setup is as follows:
9MB torch
9MC Powder feeder
Argon only
1000 amps
47 volts
45 g/m feed rate
724 nozzle
standard electrode
primary 90 psi @ 212 scfh
Part we are spraying is an aerospace component. 7.5" diameter. Top of diameter to radius is 3"
samples have all passed through the lab, good microstructure and tensile strength exceeds 10k psi.
when it comes to the part, we seem to be always having cracks. I use 2 external cooling jets combined with air frontals on the gun. table speed set to 300rpm with a 20mm step. 3.5" standoff.
i feel as so that the part is reaching too high of a temp during the spray process vs the samples and bond bars ( between 220 and 275 f ). depending on the amount of passes we do.
any suggestions as to why this could be happening? or a better way to control the temp? any input will be greatly appreciated!!
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