Hi PV
to the Surface Engineering Forum.
Pre-heating in general should be beneficial for all thermal spray processes if done properly. Pre-heating in most cases is not employed with arc spray. Mainly, because the gun itself can not be used to pre-heat substrate. Also the arc spray process does not give off water as a bye-product of combustion so water condensation on cold substrates is far less of a problem. Assuming no contamination/oxidation of substrate surface - hotter substrates generally give better bonding than colder ones. Also, in some cases pre-expanding the substrate prior to spraying can have benefits in reducing stresses in the coating.
What is the substrate?
What is the coating?
How are you pre-heating and to what temperature?
One the whole I agree with Len's comments, but
Quote:'Flame torch' preheating directly onto prepared surface will cause surface oxidation that will be detrimental to bonding.
well this depends very much on how you do it