PTAW vs. PAW (ASME IX Table QW-257.1)

[bekks]

I saw this question was asked previously, but I wasn't quite satisfied with the answer.
I've been doing some digging and can't determine the difference between PTAW and PAW. I read that the T is whether "it" is transferred and I have concluded that "it" is the arc that is transferred, but I haven't found a good description comparing non-transferred and transferred. I did come across multiple statements that seem to suggest that "it" is the filler metal being transferred via wire or powder, but I am fairly confident that is incorrect. I am not confident that any combination of wire and powder can be used with both PAW and PTAW. I would like to understand the differences between the two, but this boils down to whether I'm using Hard-facing Overlay (HFO) or Hard-facing Spray Fuse (HFSF) in Table QW-257.1.

 

[CWEng]

PAW can be transferred or non-transferred.
Whether the process is transferred or non-transferred is dependent on the welding current circuit. For transferred, the circuit/arc goes from the torch to the workpiece. For non-transferred, the circuit/arc does not go though the workpeice, but from the tungsten electrode to the torch nozzle.

 

[bekks]

Thank you CWEng. So with a transferred arc, you have the arc heating your workpiece in addition to the heat of the plasma? This way you can customize the melt of your base metal, whereas, with PAW you are melting your powder "onto" the workpiece. So your metallurgical bond with PAW is less predictable? Am I getting it?

 

[EdStainless]

I don't see that one is inherently better than the other.
In T you are working at much higher voltages for the same plasma energy.
If the arc is actually impinging on the work piece, then you aren't running Plasma are you?

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[CWEng]

The arc is somewhere around 10,000 degrees F with either method, so it sufficiently heats and melts the base metal with either method. The main difference is for keyhole welding, which you aren't doing.

 

[bekks]

Sorry, slow response.
I can certainly see the application for keyhole welding with PTAW. It seems that PTAW is also typically used for overlays and I'm leaning towards believing PAW is more appropriate for hard-facing spray fuse per Table QW 257.1
Thanks for the help, I think I've got it straight enough now.