interface contamination

[Brent]

I have recently gotten back results on a test piece of Wc-Co 88-12 hvof coating, I passed all the criteria I was supposed to meet but the interface contamination, I have done some reading on simular posts and if I understand right the problem is in the grit blasting. I used a f20 aluminum oxide grit at 80psi in our pressure type grit blast cabinet. My thought is maybe the surface was too rough. It had an 235u Ra? The angle that I blast at is around 60* and 6" standoff should these be changed. The substrate material was a piece of 4" x 1" X 1/16 thick A36 mild carbon steel.
Any pointers would be appreciated.
Brent

   

[kschewe]

Lower the pressure or use a different media like glass bead for hvof.

[sam xu]

HI Brent：
Some suggestions：
1.check your grains，Does your blasting machine have some sieves to filter dust and broken media? if not,replace new media and try again.（we have got the same problem,we changed new media ,then ok）.
2.In my opinion,your media seems too coarse,F40 or F36 is coarse enough.

[derek]

We use F16 and 32 psi, it works.

[loriolo]

Hi Brent
What about sand blasting time?, it seems that the surface is quite irregular, I can see a blast profile not so good, change the blast media and be carefully with the blasting time, some grains are under the blasting profile???.

[Brent]

Hi Brent
What about sand blasting time?, it seems that the surface is quite irregular, I can see a blast profile not so good, change the blast media and be carefully with the blasting time, some grains are under the blasting profile???.

The grit was changed out prior to blasting but I wasnt quick with my blasting time. I will try a lower pressure to get less of a profile and spend less time on the blasting of the samples. How much anchor tooth profile am anchor tooth profile I am looking for?? i