HVOF coating the bores of thin wall sleeves
06-23-2011, 12:27 PM, (This post was last modified: 06-23-2011, 12:32 PM by SDA.)
#1
HVOF coating the bores of thin wall sleeves
Hello All,

I currently have an issue with cracking of 86/10/4 coatings in the bores of thin wall sleeves. We pre-heat to 100 deegrees and run a feed speed of 60mm/min on a 250mm bore. The temperature is kept between 100-160 and the gun angle is approximately 30 degrees whilst keeping to standard Praxair settings. Can anybody help improve this method to reduce the likelyhood of cracking ?

Thanks.
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06-23-2011, 03:08 PM,
#2
RE: HVOF coating the bores of thin wall sleeves
What is the material of the sleeve? Is it stainless steel or carbon steel? Are you seeing compressive or tensile cracks?
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06-23-2011, 03:26 PM,
#3
RE: HVOF coating the bores of thin wall sleeves
Hi,

It is a Stainless Steel and the cracks appear to be tensile.
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06-23-2011, 10:00 PM,
#4
RE: HVOF coating the bores of thin wall sleeves
If the cracks are tensile, then the coating is contracting more than the stainless steel. Therefore, you must get the substrate hotter or cool the coating while spraying to increase compressive stress. If, on the other hand, the cracks are compressive, then you must do the opposite. Are you reporting temperatures in celcius or fahrenheit?
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06-24-2011, 01:23 PM,
#5
RE: HVOF coating the bores of thin wall sleeves
Thanks, temperatures are Celcius. I have also increased the feed rate to achieve 0.00035" per pass and will have the results on Monday.
Reply
06-27-2011, 04:51 AM,
#6
RE: HVOF coating the bores of thin wall sleeves
try changing your spray angle if you can. hvof likes to be sprayed straight on to the substrate.
Reply




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