HVOF super low DE%
05-24-2018, 06:48 AM,
#1
HVOF super low DE%
Greetings!

I've just transferred from one thermal spray shop to another, and I'm seeing something extremely disturbing. Let me give some context:

At my old shop, we used to using a Hipojet 2700 spraying WC-Co or WC-Cr-hastelloy powders, and I typically used somewhere around 1lb/sq ft for a 0.013-0.015" coating. At one point, we figured we had about a 65-70% deposit efficiency.

This new place has a JP 5k to spray a WC-CoCr, and it's a beautiful setup, but their deposit efficiency is blowing my mind, and not in a good way. I haven't actually done a DE experiment with weighted parts and a controlled surface area, and I think I don't necessarily need to in order to identify the presence of a serious problem. They typically use 3-4.5lbs/sq ft for a coating of the same thickness, and the coatings tend to be inferior in at least the bond strength parameters.

They use Praxair's recommended settings for the powder/machine setup, which makes me wonder if those settings are reliable or not. If not, knowing that could solve a lot of problems. If the settings ARE reliable, I'm at a loss to explain just why the DE is so terrible.

If anyone has any ideas, please let me know.
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06-11-2018, 10:34 PM,
#2
RE: HVOF super low DE%
Im not sure of your hardware set up etc but it's not an "apple for apples" situation.

The "hipo Jet" uses an axial powder feed instead of the radial feed of the JP which in my experience provides better DE, but keep in mind even with a Diamond Jet you will normally only get around 50% DE - 70% for a Hipo Jet would be extremely good!.

In saying that you may be able to increase your current DE by increasing the barrel length.

When I sprayed 88/12 (Wc/Co) in the past using JP we used an 8" barrel.

Are you using the same powder? Grain size, shape?

Check your feed lines for leaks too?

Cheers
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06-14-2018, 12:15 PM,
#3
RE: HVOF super low DE%
Hi! Victor,
How you determined / measured the DE? can you please explain a bit?
In JP5000 you have to increase your O2 & Kerosene flow to get more deposition. When is your system calibrated last?

Regards,
Krishan
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