Wc/Co Coating wear.
03-07-2012, 07:12 AM,
#1
Wc/Co Coating wear.
At my work we recently had a stainless shaft come back that needs to be redone. The shaft is stainless steel 3" dia with a WcCo coating over a 75B build-up. I have no previous parameters to go by on what was done I can assume that the Wc coating is .007" thick and the 75B build up underneath may be .050" thick. The reason for failure in the customers eyes is the wear in the seal areas they don't feel this shaft has stood up as well as others we have done in the past. I am wondering if this type of wear is from the coating not being hard enough??? What would I be looking to do different change powders, barrel length? As I said the previous sprayer didn't keep very good record so I have no past info to go off.
The coating is being applied with a Jp-5000
Cheers Brent
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03-07-2012, 09:43 AM,
#2
RE: Wc/Co Coating wear.
Is this the same coating you have used for all of the other parts ?

If it is, something has to have changed to produce a softer coating. Go back to basics

Check your spray distance, feed rate and speeds and feeds (I used to go on approx 0.005" per pass - 0.001" for a repeat)

I would spray a 3" dia at 313 rpm and 31mm/s traverse

if they are all fine look at increasing the speed of your flame - faster particles = a more dense coating

whats the composition of the Powder you are using ?

is it 88 Wc 12 Co or 86 Wc 10 Co 4 Cr ?

See how you get on with that. There are other factors it could be but they are a starting point

Cheers
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03-07-2012, 02:45 PM,
#3
RE: Wc/Co Coating wear.
I believe you need post finishing the Wc/Co coating to achieve the surface request. If you put too much 75B coating on part, there will be less Wc/Co coating on part, this could be the reason of coating failure.
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03-08-2012, 06:23 AM, (This post was last modified: 03-08-2012, 06:27 AM by Brent.)
#4
RE: Wc/Co Coating wear.
(03-07-2012, 09:43 AM)KevGarty Wrote: Is this the same coating you have used for all of the other parts ?

-I will be using the same powder

If it is, something has to have changed to produce a softer coating. Go back to basics

-the last spray guy kept no records

Check your spray distance, feed rate and speeds and feeds (I used to go on approx 0.005" per pass - 0.001" for a repeat)

-the spray distance calls for 13" seems close to me??

I would spray a 3" dia at 313 rpm and 31mm/s traverse

- My traverse will only run 22in/min(9.5mm/s) so that is something I think the owner needs to address

if they are all fine look at increasing the speed of your flame - faster particles = a more dense coating

- I am going to increase to a 6" barrel to increase particle speed

whats the composition of the Powder you are using ?
is it 88 Wc 12 Co or 86 Wc 10 Co 4 Cr

- it is a 68Wc 12 Cr 6 N 5 Co

See how you get on with that. There are other factors it could be but they are a starting point

Cheers


(03-07-2012, 02:45 PM)derek Wrote: I believe you need post finishing the Wc/Co coating to achieve the surface request. If you put too much 75B coating on part, there will be less Wc/Co coating on part, this could be the reason of coating failure.

They always aim for .007" per side after finishing for hvof in our shop. So I can assume that the shaft had that amount of hvof spray on it last time. Would increasing the depth of spray help with this type of wear??
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03-08-2012, 11:15 PM, (This post was last modified: 03-09-2012, 06:05 AM by KevGarty.)
#5
RE: Wc/Co Coating wear.
9.5mm/s is a bit slow in my opinion and the coating will be building up too quickly. Coatings perform better applied in small layers (around 0.004 - 0.005" per pass) thats the rule of thumb I used to work too your employer might be different but I didnt have too many problems working to that method.

If you put the 6 inch barrel on back off the Spray distance slightly maybe to 14 or 15 " I've never used a powder with a composition the same as you mentioned but I have used 86/10/4 and 88/12 and similar and the spray distance was 14" with an 8 inch barrel

As far as the other sprayer goes, stick your foot up his back side for not keeping records Wink







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03-12-2012, 12:00 PM,
#6
RE: Wc/Co Coating wear.
If the other pieces worked properly, you will check the coating micro hardness, maybe you take off all the Wc/Co coating.
Best regards
Luigi
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