WC-Co coating porosity |
11-23-2010, 09:58 AM
Post: #1
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WC-Co coating porosity
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? | |||
11-23-2010, 01:31 PM
Post: #2
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RE: WC-Co coating porosity
Hi Zhiguo
![]() 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. Regards Gordon www.gordonengland.co.uk www.surfaceengineer.co.uk Photography Obsession | |||
11-24-2010, 02:55 AM
Post: #3
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RE: WC-Co coating porosity
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 | |||
11-29-2010, 06:18 AM
Post: #4
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RE: WC-Co coating porosity
its all about parameters. i use the st gun and most of the coatings are less then .5%
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11-30-2010, 09:01 AM
(This post was last modified: 11-30-2010 09:07 AM by Zhiguo.)
Post: #5
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RE: WC-Co coating porosity
(11-23-2010 01:31 PM)Gordon Wrote: 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? (11-24-2010 02:55 AM)Simon Kim Wrote: Hello Zhiguo, Thank you Simon! (11-29-2010 06:18 AM)kschewe Wrote: 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! ![]() | |||
12-01-2010, 09:03 AM
Post: #6
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RE: WC-Co coating porosity
Hi Zhiguo
Quote:Hi Gordon, 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. Regards Gordon www.gordonengland.co.uk www.surfaceengineer.co.uk Photography Obsession | |||
12-02-2010, 08:44 AM
Post: #7
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RE: WC-Co coating porosity
(12-01-2010 09:03 AM)Gordon Wrote: 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. | |||
12-15-2010, 08:08 AM
Post: #8
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RE: WC-Co coating porosity
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!
Workholding | |||
12-16-2010, 09:08 AM
(This post was last modified: 12-16-2010 09:10 AM by kschewe.)
Post: #9
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RE: WC-Co coating porosity
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 | |||
12-24-2010, 07:21 AM
Post: #10
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RE: WC-Co coating porosity | |||
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