Posted by Gordon England on March 19, 2004 at 01:53:59:
In Reply to: Ceramic coating on Polyurethane posted by Chris on March 16, 2004 at 18:00:53:
: Dear Sir,
: Is ceramic coating on polyurethane possible ?
: The component is made of polyurethane on which slurry, iron ore and coal circulate at ambient temprature. The material has a tendency to adverse against the polyurethane surface. PH value is normal. The rotating speed is a min of 2 meters per cubic hour with a maximum of 10. We would like to know -
: What kind of ceramic can be used ?
: What is the maximum thickness that can be built up ?
: Can 9 Mohr scale hardness be acheived with ceramics ?
: We would also like to know if tungesten carbide can be sprayed on polyurethane surface.
: If yes what are the pre cautions that need to be taken.
: Are there any other options ?
: Thank you in advance.
: Chris
:
Hi Chris
A cautious yes to your first question. Most oxide ceramic and carbide type materials that can be thermal sprayed may be possible with the right preparation, bond coat and thermal spray procedure.
I have sprayed chromium oxide, alumina and tungsten carbide/17% cobalt onto specially prepared glass and carbon fibre reinforced polymer tubes to 0.012 - 0.016" but unfortunately this does not always apply in every case. Some plastic substrates just reject any coating.
The hardest thermal spray ceramic that I know of is chromium oxide reaching about 1800 HV/1 (8-9 moh's)at best. Alumina is normally around 1000 HV as the coatings contain softer metastable phases unlike the hard alpha phase found in bulk alumina ceramics.
The only way to know for sure if a thermal spray coating can be successfully applied is to try it. In my experience some development work is usually required in each new application case. Spraying onto polymers is extremely technique dependent and following the general guidelines for spraying onto metallic substrates will almost certainly result in failure.
Other options - ceramic tiles?
Why polyuretane substrate?
Regards Gordon
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