can someone explain this :)
10-03-2007, 02:44 PM,
#1
can someone explain this :)
Higher particle temperature can also result in higher tensile stresses in coatings which is undesirable.

Can someone tell me why this is the case and why it is not desired???

thank you Smile
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10-05-2007, 02:55 PM,
#2
RE: can someone explain this :)
Hi Intel55

Quote:Higher particle temperature can also result in higher tensile stresses in coatings which is undesirable.
It is important really to know in what context this statement was made.

First, tensile stresses in many thermal spray coatings are a fact of life, they form mainly from solidification and cooling shrinkage (see https://gordonengland.co.uk/tsc.htm#STRESS. The higher the tensile stress the more likely cracking and delamination will occur in the coating. Coating thickness plays a big part here as well, the higher the tensile stress the lower the coating thickness limitation.

I assume the statement is in context with thermal spray process types, like comparing plasma to HVOF to cold spray (cold gas-dynamic spraying). Both particle temperature and velocity are important. Generally the lower the temperature and the higher the velocity of particles the less tensile stresses are generated. In fact some HVOF and cold spray produce coatings with compressive stress. This is because there is less solidification and cooling shrinkage involve and an increase in mechanical deformation of the particles on impact.

Hope that helps Big Grin
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10-08-2007, 01:58 PM,
#3
RE: can someone explain this :)
Thanks for the help Gordon.

I got the question from a friend when we were discussing the pros/cons of the JP5000 gun versus the DJ2700. The JP5000 coats in compression b/c of the lower particle temps versus the DJ. But the DJ is better on CrC b/c of the higher temps than the JP, in his opinion. JP wins on WC-Co though.Cool
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