Using arc gun in place of PTA

[steve3884]

I am inviting thoughts and suggestions regarding the following app. We have a fly-ash conveyor screw that had the stub end previuosly PTA sprayed with Wc/Co. The stub rides in a support saddle coated with ceramic. We have an arc gun (no PTA) and would like to coat the stub with a wear and corrosion resistant material (subject to SO²) and apply a phenolic sealer. Any suggestions as to wire chemistry? Would an arc sprayed coating on this heavy screw be durable enough to withstand?
Thanks for any comments.

[djewell]

You can buy WC and CrC hardfacing wires to arc spray. You will be limited to max 50% carbide in the coating. It may work for a while, but it will not have nearly the bond strength of the PTA coating. I suggest you should look at a high velocity process. This will allow you to spray a higher carbide content coating and achieve a higher bond strength. Contact me off-line if I can help you with this. I have some experience spraying fly ash conveyor screws.

[Stephen Booth]

Hi Steve, I assume you are the owner of the Screw Conveyor, and want to repair the part yourself. If this is the case, and you do not want to invest in HVOF, then you might consider welding or brazing. In the past years before PTA was available these screws were welded (and continue to be welded) using a variety of processes, but FCAW and GMAW or GTAW would be my choices. Check with a Hard Facing Product company like Eutectic or Welding Alloys or Deloro Stellite for the consumable.

If you are a job shop, then like Mr. Jewell says a HVAF or HVOF is good for this most of the time, if you can get good surface preparation on the component.

Good luck, and let us all know how it works out

[Vijay Deshpande]

Spray Fuse process using tunsten carbides cobalt base self fluxing powders using flame spray gun will also work. Good luck