APS WC coating delamination

[brianf121]

Hello all,
I am new to this forum and am in need of some help. I work for a company that uses the Northwest Mettech Axial III spray system to spray WC powder onto a thin steel substrate (as low as 0.015”). We have run into some issues, namely poor porosity and delamination from the substrate and in the coating itself. We seem to have corrected our porosity issue by using a finer grain of powder, but that has only served to increase the amount of delamination we are seeing. Typically our coating needs to be anywhere from 0.005” to 0.012” thick. Is there anything short of purchasing an HVOF system we can do to reduce the amount of delamination?

Thanks in advance
Brian

[djewell]

Delamination occurs when the stress in the coating exceeds the bond strength to the substrate. To solve your problem, you need to increase bond strength or decrease stress. Using the finer powder increases the coating stress because the molten particles contract when they cool and solidify. If you are doing a good job preparing the surface for spraying, you could try applying thinner layers or a bond coat. Otherwise, I would suggest going back to the larger particle size and working on another solution for the porosity problem.

[brianf121]

djewell thank so much for responding