Pure argon will be the major stumbling block for this weld.  You need a minor bit of O2 or CO2 to stabilize the arc.  With cladding you want to minimize dilution, so the tri-mix recommendation is ok, but since tri-mix contains helium to aid in penetration and wetting with short arc, you probably want either 1 or 2% oxygen/argon, or up to 5% CO2 for your pulsed spray cladding process to minimize penetration and dilution.  With steel spray arc, O2 tends to give a deep finger of penetration, and I'm not sure if this would be the case with inconel, but something to think about, maybe the CO2 would give a more uniform penetration shape.

A couple other things to think about.  A push torch angle give a flatter, lower penetration weld shape.  DCEN gives less penetration than DCEP with pulsed spray MIG.  20+ years ago I was involved with trying to develop a mechanized vertical down stainless steel cladding procedure with the Dimetrics pulsed spray MIG (the Metal Beam).  This machine was sophisticated for it's time with adjustable frequency to 1000 hz, but if you have a Lincoln Power Wave or similar machine, surely you can tune the wave form to make this process sing.

I did some work with this waveform for a Navy project and you will need to do tweaking.  This work was presented in Las Vegas this past year at the Weld Show.  We were working with 0.045 Alloy 625 up to 400 IPM.  The biggest problem I had with GMAW-P (we looked at SAW, PTA and GTAW too) was that the arc was very stiff and columnar, so you get great dig, which is not a good thing for cladding.  If you can feather out the arc, you should be more successful than I. 

We worked with two mixed gasses, 66 Ar - 33 He - 1 CO2 and there was good wetting but increased penetration, and Ar with just a touch (<1%) CO2 and there was low dilution but poor wetting.  You need He in the gas, but I think more like 10-20% would get the wetting without sacrificing the dilution.  You do not need much CO2 to stabilize the arc, with less than 1% we had a very stable arc. 

Because of the poor wetting, oscillating with this setup was very difficult.  We noted poor first layer dilution (>25%) with this process.  Basically at the edge of the oscillation you needed to dwell to get good tie in and give the puddle time to fill in the toe, but you sacrificed dilution. 

All of these issues, plus the Cr IV concerns pushed this process out.  We ended up with GTAW qualifying hot wire at over 10 lb/hr. 

When you talk to Lincoln, ask for the newest mode 175 waveform.  It is much smoother than the older versions of the waveform.