Thermal Sray Newbie
11-02-2011, 04:38 AM,
Thermal Sray Newbie
Hello I am new to this forum and the world of thermal spray. I have been given the task of HVOF operator at my workplace. I have had training in the start up of our equipment (Tafa JP-5000) but no formal training on the application of coatings. Some of the info I do have comes from books, what I have read about on this site ( I think we are referred to as lurkers Big Grin ) and a co-worker running our twin arc wire.
One quick question would be does rotational direction of the substrate matter in relation to the gun? And also the height above or below center line? I have tons of other questions but I will wait on them till I have some spray time behind me.
11-16-2011, 11:35 PM,
RE: Thermal Sray Newbie
Hi Brent,

As far as rotational direction goes this makes no difference to the coating application, however the centre line does have an effect on the coating deposition if it is too high/too low the deposition will be reduced. Ideally you want the spray to be dead in the centre of the part at a 90° to the surface.

If you need anything just give me a shout I'll let you know if I can help

11-17-2011, 05:42 AM,
RE: Thermal Sray Newbie
Totally agree with Kev on the rotational direction having no impact on coating. I always believed that the gun/spray stream should be straight through the middle (Antipodal point)......But recent evidence supports spraying slightly off centre particularly with HVOF. The reason is that some spray bounce back occurs from the work-piece surface back into the spray stream. The ‘spent’ and re-entrapped particles results in ‘undesirables’ and subsequently compromised coating quality. Obviously going further and further away from the centreline will result in increasing lesser coating quality and DE.
Len Wood
Ph: +64 9 4730705
Fax: +64 9 4730706
11-17-2011, 05:50 AM,
RE: Thermal Sray Newbie
Everyday is a school day ! Cheers for that

11-19-2011, 05:19 AM,
RE: Thermal Sray Newbie
Yes everyday has been like a school day learning to successfully setup and spray parts. Thanks for your replies, the jobs I have done in the last few weeks is with the gun just above the center-line (4-6"dia.part) and rotating counterclockwise. My biggest challenge now is keeping the parts cool. I have a airline pointed from underneath at a fixed position cooling while I am spraying. I may try and make a couple air lines that follow on either side of the spray stream and see how that works for more even cooling.

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