Gordon England Surface Engineering Forum



Re: T800 Coating Thickness limit by HVOF

Posted by Alex (192.35.25.6) on 01:38:13 31/03/06

In Reply to: Re: T800 Coating Thickness limit by HVOF posted by Alexei Goncharov

Thanks for all the recommendation.
To update, I have tried some preventive action and seems the lifting or delamination has been improved significantly.
1. As recommended by Gordon, I have put part temperature monitoring into place, making sure that the part temp. would not exceed 120oC at all time. stop-spray method,for sufficient part cooling-off period.
2. I make sure the preheating is done with the preheating temp. of 120oC~~130oC. Would it be ok? too much or higher better?
3. I have changed corrodum grit size from 60 to 46, creating a much rougher surface. and make sure all best practises observed after grit blasting. And make sure all edges are blasting effectivel with Ra above 150 uin.
4. Use M.E.K to wipe the part if any touching is done to remove contamination.
5. I have also chamfered the edges to about 30o. As the edges of flange thickness is limited, so, it's hard for me to have a 45o chamfering. What would be the best undercutting or chamfering angle in this case?
6. Also, I practise clearing of overhang coating at each stop(cooling) to allow exccesice ooverhang coating build-up.
These area some practice I would like to share to have put a stop to the lifting problem.
The next problem I have is the edges chippings during benching of the overhang coating. I m still trying to solving this problem like reviewing the benching methods and so on. Any opinion and advice on this area?
Thanks for all the advice.
Regards,
Alex Chan


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