smooth as-sprayed carbide coatings
04-25-2009, 12:25 AM,
#1
smooth as-sprayed carbide coatings
Hi folks....I'm after some information about how smooth (< 14microinch Ra, < .35micron Ra, > 320 grit) carbide coatings are produced as-sprayed, with no grinding. I'm trying to duplicate a WC/Co coating that I have that I am almost 100% certain was not ground. However, almost all thermal spray shops I talk to say that it's near impossible without a secondary grinding operation. What's going on? Would this require very specialized equipment or powder?
Reply
04-25-2009, 12:50 PM,
#2
RE: smooth as-sprayed carbide coatings
Hi durkie

You will struggle to get much below about 100 microinch (2.5 micrometre) Ra for as-sprayed surface texture with HVOF carbide coatings and that's even with using the finer grade powders on very fine grit blasted or non-grit blasted substrates. 14 microinch Ra is practically not far off a ground finish.
Reply
04-25-2009, 04:43 PM,
#3
RE: smooth as-sprayed carbide coatings
i see. the coatings i can produce now are rated in terms of grit, and the smoothest one is nominally 320 grit, which I understood to be close to 14 microinch Ra. however i've only been able to come to that number from conversion tables i've found on the internet (and even those say Ra and grit don't exactly correspond). and if what you're saying is true about 14 microinch Ra being close to a ground finish, then I have to be off in the conversion there, because this surface is still quite rough.
Reply
04-25-2009, 06:58 PM,
#4
RE: smooth as-sprayed carbide coatings
Hi durkie

The 320 grit reference is really an indication to the size of the grit in an abrasive product and the conversion to surface texture Ra is probably based on the finish obtained on steel using that product (not necessarily same as carbide coating).

I can only guess that someone has compared say the texture of a 320 grit silicon carbide grinding paper with that of a as-sprayed coating in a sight and feel sensory fashion. I would say that they are probably not too far apart Cool , but texture of abrasive grit (or as-sprayed coating) is far different to the actual finish obtained on steel using that abrasive. Hope that makes sense Happy0193
Reply
04-26-2009, 06:34 PM,
#5
RE: smooth as-sprayed carbide coatings
Yep, I think I got it. The confusing part was that the Ra of the grit -> Ra conversion doesn't actually refer to the abrasive itself (even though grit does), and that a rough surface can produce a finish smoother than itself (makes sense though).

Basically, my 320 grit coating will produce a 14 Ra steel surface finish, but the actual Ra of the coating proper is much higher.

Thanks!
Reply




Possibly Related Threads…
Thread Author Replies Views Last Post
  Machining of thermal sprayed coatings ServiceTech 4 9,520 08-14-2023, 09:00 PM
Last Post: J!m
  Request for solution to reduce porosity in HVOF Tungsten Carbide Coatings sreenuvundela 7 12,266 07-22-2020, 08:01 AM
Last Post: Simon Kim
  Environmental affect on plasma sprayed coatings nshepher 0 2,293 06-26-2018, 09:43 PM
Last Post: nshepher
  Tungsten Carbide coatings Sealants sorousheti 5 7,813 11-23-2015, 10:18 AM
Last Post: sorousheti
Information Chrome oxide thermal sprayed coatings shelf life Leanne 1 4,387 02-14-2013, 02:18 PM
Last Post: Gordon
Exclamation Cleaning Ceramic (Chrome oxide) coatings - as-sprayed Leanne 1 4,641 02-04-2013, 08:18 PM
Last Post: kschewe
  Buffer or build up layers under HVOF Carbide Coatings Stephen Booth 12 18,875 05-19-2011, 11:00 PM
Last Post: Met.Eng.
  How to smooth TBC or DVC coating derek 3 5,360 04-20-2011, 11:30 AM
Last Post: wilfred1963
  Importance of NiCr in Chromium Carbide Coatings DJr9515 2 7,751 07-17-2007, 01:31 AM
Last Post: Gordon
  SHRINKAGE OF ARC SPRAYED COATINGS Vijay Deshpande 3 10,181 02-12-2007, 11:25 PM
Last Post: Gordon
  ULTRASONIC TESTING OF THERMAL SPRAYED COATINGS Vijay Deshpande 4 11,063 01-04-2007, 08:37 AM
Last Post: Alexangel1226



Users browsing this thread: 1 Guest(s)





Surface Engineering Forum Sponsor - Alphatek Hyperformance Coatings Ltd