Posted by Gordon England on March 12, 2003 at 01:25:29:
In Reply to: HVOF Brinnell Hardness posted by Rick Mohr on March 11, 2003 at 17:19:54:
: : : When moving fluidized silicon oxide (DE) through pumps, I am interested in extending useful life of the wetted parts. One means is to select materials by use of hardness scales of the base metals. Economics of alloys leads me to consider coatings on wetted parts, such that I could use the softest, cheapest alloys such as ductile iron or cast iron. In the case of either ductile or cast iron, which type of coating and application method would be recommended and proven to yield longest service life?
: : Hi Rick
: : HVOF coatings of tungsten carbide/cobalt chromium (86WC-10Co-4Cr)or possibly plasma sprayed chromium oxide could be suitable candidates.
: : Regards Gordon
:
: Thanks for the insight, Gordon. Can you advise what the Brinnell Hardness of the recommended HVOF coatings is; tungsten carbide/cobalt chromium versus chromium oxide?
Rick
You can not measure the hardness of these coatings using Brinell nor convert to this scale. See http://www.gordonengland.co.uk/hardness
HVOF WC-10Co-4Cr coating - 1000-1400 HV/0.3 HV/1
Plasma Chromium oxide - 1200-1800 HV/0.3 HV/1
These are typical Vickers microhardness values and the range covers various grades of coating. These are extremely hard and well above that covered by Brinell.
Be aware that hardness is only one factor in a coatings ability to resist wear.
Regards Gordon
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