Arc spray porosity problem
05-21-2019, 04:10 PM,
#1
Arc spray porosity problem
Hello
I attached a photo from a sample spray. System is 8830. Wire is Metcoloy 2 without buffer. Sandblasted cleaned without problem. Layer thickness is 2.5 mm. Machined with lathe CBN cutters as 0.5 mm at OD passes, quite gently.

What is reason of that much porosity? How can i solve this problrm? This layer created to spray HVOF on top of it....
.


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05-22-2019, 04:03 AM,
#2
RE: Arc spray porosity problem
(05-21-2019, 04:10 PM)velocity Wrote: Hello
I attached a photo from a sample spray. System is 8830. Wire is Metcoloy 2 without buffer. Sandblasted cleaned without problem. Layer thickness is 2.5 mm. Machined with lathe CBN cutters as 0.5 mm at OD passes, quite gently.

What is reason of that much porosity? How can i solve this problrm? This layer created to spray HVOF on top of it....
.
Hi Velocity

in my opinion, try checking the nozzle, what perameter:
amperage, voltage, air pressure, because this parameter is very influential from the results of coating, I have experience, before the top layer of HVOF, I use NiAl as a buffer layer and there is no problem.

Thanks
Gito
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05-27-2019, 03:10 PM, (This post was last modified: 05-27-2019, 03:12 PM by Met.Eng..)
#3
RE: Arc spray porosity problem
I think Machining is not suitable for Metcoloy 2 , you can try Grinding with SiC wheel.

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05-28-2019, 06:48 PM,
#4
RE: Arc spray porosity problem
(05-27-2019, 03:10 PM)Met.Eng. Wrote: I think Machining is not suitable for Metcoloy 2 , you can try Grinding with SiC wheel.

just what i wanted to say
never had similar problems when grinding
when turning surface was similar to that in the picture
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05-28-2019, 08:41 PM,
#5
RE: Arc spray porosity problem
(05-28-2019, 06:48 PM)sprayloud Wrote:
(05-27-2019, 03:10 PM)Met.Eng. Wrote: I think Machining is not suitable for Metcoloy 2 , you can try Grinding with SiC wheel.

just what i wanted to say
never had similar problems when grinding
when turning surface was similar to that in the picture
It means a lot.
I will try wheel for next time. What do you suggest for 420 alloy arc spray? Green or pink? What size of grid?

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05-31-2019, 11:46 PM, (This post was last modified: 05-31-2019, 11:55 PM by Met.Eng..)
#6
RE: Arc spray porosity problem
Hi again,

U can use Green GC wheels, GC60 J11 VR or GC80 this wheel is soft Green SiliconCarbide , and medium grit, If u try Ping or white AluminumOxide wheel you have to drees wheel after one or two pass we always use soft green SiC wheel for AISI 420, 431 ect.



Good luck Smile
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06-01-2019, 01:19 PM,
#7
RE: Arc spray porosity problem
Thank you Smile I tried to find but green sic wheels are not standart as 60 grid size so i tried pink. It worked somehow. And i have alimunim oxide bacalite bonded rough grid wheels, they also worked fine in beginning but after granuler layer cleaned, performance getting much worse. So maybe i will clean granuler (first sprayed) layer with wheel then finish with 60 or 100 grid diamond belts.

I know i have to find green sic 60 grid wheels for one step solution but it will be custom order so for 2 months i will try all your suggestions Big Grin
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