Anne,
Plasma and HVOF are quite different coatings.
Pores in the plasma coating will be interconnected in most of the cases. Could glue penetrate 150 mkm deep?
Normally - no. You could see the level of penetration in some microstructures, and it is not deep.
HVOF coating will have as-sprayed porosity at the surface level, but good HVOF or HVAF coating will have close to zero porosity below.
So you will not have a chance to reach the substrate with a glue.
There is an instrument to test gas permeability of different coatings, which could help to predict possible level of sealant penetration (and possible corrosion and wear resistance!)
http://www.kermetico.com/equipment-gastest.php
Regards,
Vitaly