WC-Co coating porosity

[Zhiguo]

Problem with coating porosity. I spray the WC-17Co powder with JP5000ST HVOF gun.

Hello,
Nice to meet you all!
I have a problem with coating porosity. I spray the WC-17Co powder with JP5000ST HVOF gun. But the porosity is always higher than 2%. How can I decrease that? What porosity value can be obtained with this kind of machine?

And another question, what is the difference between JP5000 and JP5000ST gun? which one is better?

[Gordon]

Hi Zhiguo

to the Surface Engineering Forum.

How are you measuring the porosity and which WC-17Co powder and parameters are you using?

JP-5000ST gun produces a narrower more focussed spray pattern (ST = Small Target), intended for spraying smaller parts with more economic powder usage. So I would hazard a guess that the JP-5000 may produce better quality coatings in generally.

[Simon Kim]

Hello Zhiguo,

I have also some experience for WC17Co (Diamalloy 2005NS).

That has lower recovery than WC12Co and low thickness per pass.

I knew last week after test spray, thickness and porosity are related to distance greatly.

I wish your successful result.

And would like to say thanks to Gordon for good explain about differance point.

Simon

[kschewe]

its all about parameters. i use the st gun and most of the coatings are less then .5%

[Zhiguo]

Hi Zhiguo

to the Surface Engineering Forum.

How are you measuring the porosity and which WC-17Co powder and parameters are you using?

JP-5000ST gun produces a narrower more focussed spray pattern (ST = Small Target), intended for spraying smaller parts with more economic powder usage. So I would hazard a guess that the JP-5000 may produce better quality coatings in generally.

Hi Gordon,
Thanks for you good answer!
We measured the porosity by a software under the optical microscope.
The powder is H.C.Starck Amperit 526.727. Particle size 15-45um.
The parameters are: Kerosene 14l/h, oxygen 680NLPM, Carrier gas 6NLPM, spray distance 275mm, powder feed rate 60g/min.
Are the parameters good?

---

Hello Zhiguo,

I have also some experience for WC17Co (Diamalloy 2005NS).

That has lower recovery than WC12Co and low thickness per pass.

I knew last week after test spray, thickness and porosity are related to distance greatly.

I wish your successful result.

And would like to say thanks to Gordon for good explain about differance point.

Simon

Thank you Simon!

---

its all about parameters. i use the st gun and most of the coatings are less then .5%

kschewe ,
Do you spray WC-Co powder? Could you please tell me what parameters are you using? Is the porosity level good?
Eagerly hope for your kindly support!

[Gordon]

Hi Zhiguo

Hi Gordon,
Thanks for you good answer!
We measured the porosity by a software under the optical microscope.
The powder is H.C.Starck Amperit 526.727. Particle size 15-45um.
The parameters are: Kerosene 14l/h, oxygen 680NLPM, Carrier gas 6NLPM, spray distance 275mm, powder feed rate 60g/min.
Are the parameters good?

I can't say whether parameters are good or bad, just not enough experience with system or powder. I would expect better than 2% porosity though under good spraying conditions.

I have got to say this first, before we start messing with parameters and powders - Check that your coating metallography testing methods and procedures are in fact giving accurate and consistent results. All too often I have found this to be a problem. Also, be careful not to be too trusting in computer image analysis software unless it has been thoroughly tested and calibrated to this type of work.

I would try producing a coating using a Praxair equivalent powder where there are official recommended parameters and certain quality expectations. This will give you a baseline for comparison and a good starting point for coating development. Unfortunately, many powders of apparently similar specifications, may not necessarily produce coatings of equal quality or deposit efficiency.

[Zhiguo]

I have got to say this first, before we start messing with parameters and powders - Check that your coating metallography testing methods and procedures are in fact giving accurate and consistent results. All too often I have found this to be a problem. Also, be careful not to be too trusting in computer image analysis software unless it has been thoroughly tested and calibrated to this type of work.

Thank you Gordon! Yes, I think I have to discuss the metallography testing methods with our Lab engineer.

[ives]

Well, I too had some hard time dealing with this porosity issue and what I did was to spray with the exact same gun. Later, I found out that most of the issue lied with the ST gun. I changed the gun and everything was working pretty fine since then!

[kschewe]

for the jp5000st
1050 o2
3.6 fuel, i use varsol.
8" spray distance.
For hvof most of the parameters are very similar, unlike plasma. Hope that helps
spray the finest particle size powders for hvof. Find tafa powders

[Zhiguo]

for the jp5000st
1050 o2
3.6 fuel, i use varsol.
8" spray distance.
For hvof most of the parameters are very similar, unlike plasma. Hope that helps
spray the finest particle size powders for hvof. Find tafa powders

What is your powder feed rate?