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Heat Tint discolourations

Heat Tint discolourations

Heat Tint discolourations

(OP)
I have a stage 1 bucket with a PtAl bond coat on the aerofoil.

We applied a EB-PVD Thermal barrier coat to the aerofoil which spalled. The shank and root of the bucket did not have any PtAl or PVD which we wanted, although there was a green colour to the uncoated regions.

We stripped the PVD using KOH strip, washed the bucket until the solution was at a neutral PH.

A blast was performed.

A heat tint was perfromed at 700 degrees

The aerfoil was gold - as expected

The root and shank of the bucket was also gold- this should have been blue due to the presence of no coating.

My question is : could the KOH strip be the reason for the gold appearance?

Or is the green discolouration from the PVD a more possible reason.

i would apprecitate any help!

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