×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

HVOF Coating Thickness
2

HVOF Coating Thickness

HVOF Coating Thickness

(OP)
I've been looking into hardface coatings on pipeline Ball Valves and was wondering what the typical coating thickness was for HVOF Tungsten Carbide on balls and seats. Are there specific minimum/maximum coating thickness limits that give the best performance?
Does the thickness put down depend on the properties of the fluid in the line? i.e. thicker coating to reduce effects of erosion?

Thanks

RE: HVOF Coating Thickness

400 micron is a good place to start.  Any thinner and the erosive resistance isn't what you want...and much thicker and the TCC doesn't have the mechanical strength and ductility to resist shear forces in the seating and can flake or crack.

RE: HVOF Coating Thickness

Iylek,

Valvit is correct 400 mic is a good place to start but still its depends upon as you said the fluid in the line?
Mostly we are applying bond arc after the surface preperation of the base material and then final coating, which gives good strenghth.
 

RE: HVOF Coating Thickness

I work in the subsea and the most common thickness is 150 to 200 micron finished grinding and lapping. The TOTAL Oil Company is the only company requireing 400 micron. Thicker coating may crack.
Applied on gate and ball valves all sizes in direct contact with well stream. Base material need to be CRA materials as SuperDuplex or Inconel for hardness. This to avoid denting.

RE: HVOF Coating Thickness

400 micron is required only by Total Spec. The std thk. is 150 or 200 micron and, if the adhesion is ok, is enough for any service. Moreover, a bigger thk. is fragile and doesn't add anything to the hardfacing point of view.

RE: HVOF Coating Thickness

Nilsoni & Engtipgb,

You may refer to the old revision of TOTAL Spec. In my understanding, TOTAL Spec requires 300 micron coating thickness only...

RE: HVOF Coating Thickness

(OP)
Thanks for all the replies so far. From this and other work I've done I can see that there is quite a varied opinion on coating type, mix and thickness from the powder suppliers, coaters, OEMs right through to end users - all presumably based on experience good, or bad with particular types. Doesn't make selection easy!

A few other things I haven't come across are how much the ball diameter affects the decision - presumably coating thickness will change with ball diameter, or does it stay the same? Are thicknesses on ball valve gates and seats typically the same as on gate valves?

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources