WC-Co by HVOF on Monel Ball valve

[raviswanadha]

Hi all,
I need your suggestions and solution to the problem we are facing.
We have WC-Co by HVOF on Monel Ball valve to work in "Ammonium Bifluoride with excess Hydrogen Fluoride" media. The customer has complained that the coating is wearing faster. A brief description is given below
Service Temp - 285F
Pressure - 3 to 5 psig.
Media - Ammonium Bifluoride with excess Hydrogen Fluoride
Min/max on temperatures - Ambient to 285F
Flow rate - <1/2 GPM
Required shut off - Class VI
Cycles per day - 24
Ball Valve, Size 25mm Class 800, Full bore, Seat they are using right now is Glass filled PTFE.
Can you suggest what could be the problem And also any alternate material to be sprayed on this.
regards

[Spraytube]

Hi,

Your issue is cobalt matrix, for example, Ammonium bifluoride in addition with some acid is use to extract cobalt from certain kind of soil in mining industry.

Simply switch your matrix to a Ni/Cr Matrix.

Regards

[raviswanadha]

Hi,

Your issue is cobalt matrix, for example, Ammonium bifluoride in addition with some acid is use to extract cobalt from certain kind of soil in mining industry.

Simply switch your matrix to a Ni/Cr Matrix.

Regards

Hi thanks for your post. so you suggest we us Tungsten carbide with Nickel binder instead of cobalt binder?
regards

[Spraytube]

Hi,

Sorry my explanation wasn't clear enough.
I was thinking about a WC 10Ni 5Cr.

Using Ni/Cr binder will helps to have a better resistance to corrosion.
With this kind of powder you will have a higher hardness than WC/Ni coating (consequence of the hardening effect of the chromium in the binder) but the toughness will be reduced...

Regards

[raviswanadha]

Thank you very much for your valuable suggestion we will try with that composition and will post back the result
regards