HVOF - MCrAlY coating issue

[*Plasma Junkie*]

   


Hi All,
Been developing an overlay MCrAlY coating on a very thin surface. Surface gets as thin as 0.0500" in places.
The main problem ive seen with the 1st attempt was... the HVOF coating 'rolls -off' on the edges of my sprayed surface and even sprays to almost a point on thin areas!! I'll try and attach a pic.

I need to build up almost 1mm of overlay, but i also need that 1mm on the edges too!!!

My next trial... as this was coated at 15" standoff/ 90deg... i will introduce 70-80 degree angles to both sides etc...

anyone got any better ideas?? all tips will be greatly appreciated!

[Gordon]

Hi *Plasma Junkie*

Not much area to support a thick coating. I can only suggest forming a groove or valley recess rather than a flat surface on the substrate, so the root of the coating has more support and area to bond with. May also reduce that pointing effect on the coating.

[*Plasma Junkie*]

Thanks for the reply Gordon! I like the idea of forming the recess but its not an option on this project i'm afraid.
I plan on trying the 'variable' angle approach idea on my next trial run. Will let ya know how it goes.
Btw Gordon, what magnification is your picture drawn at? As your picture seems to show a lot of embedded grit particles on the interface lol
Really appreciated the effort!!

[Gordon]

Hi *Plasma Junkie*

Btw Gordon, what magnification is your picture drawn at? As your picture seems to show a lot of embedded grit particles on the interface lol Happy0193

yes, child like drawing, but happy if it made my words clearer.

Good luck with your project and yes let us know how you goes.

[djewell]

Could you sandwich your coating coupon between 2 masking pieces and "fill" the gap? You will need to select the masking pieces such that they do not bond to your coating.

[*Plasma Junkie*]

Thanks djewell. I tried that idea a few years ago on the sides of a part i was putting an overlay coating on. i resistence welded on 0.5mm nickel foil shims to the sides but had mixed results. As you suggested the shim bonded to the coating & was tough to remove. To be even safer i had the coating diffused before attempt to get the shim off. This helped a little but on a few of the parts the foil shim had buckled a bit and almost stopped the coating filling the gap every now & then.
Appretiate the input!!! cheers

[djewell]

What if you were to use something like nylon or teflon shims? Be careful not to melt the plastic.

[hamid6465]

hi
did you find new things about heat treatment of MCrAlY coatings??
I need some documents about microstructure transformation during of heat treatment and what happened when heat treatment of MCrAlY coating is done