Checking the Pulse of Welding Inconel

As Inconel wires are exponentially more expensive than other common wires – and are ordered in very large amounts per project – deposition efficiency (not wasting materials through spatter) is important. This is made difficult by the fact that most of this work is done out-of-position.

Another challenge is in terms of dilution – the operator must strike a balance between too little dilution (the bead falling off the pipe) and too much dilution (pulling in properties from the base metal and degrading corrosion resistance).

Pulsed MIG welding is not new by any means, but the technology has advanced considerably in the last 5-10 years. Older technologies may lack many of the benefits afforded by newer systems, including new built-in programs specifically designed for Inconel (and other nickel-based alloys) and arc control capabilities that allow the operator to dial in performance to their preferences.

A few things to keep in mind:

• The importance of Pulsed MIG: Similar to TIG applications with an Inconel base metal, Inconel weld puddles in this application tend to be stiff. Additionally, a calm arc is important to minimize spatter, and heat input must be controlled to achieve proper dilution.

Conventional MIG applications didn’t allow for long spray columns and created transfer that was borderline globular, creating excessive spatter. Pulsed MIG is ideal in this case as it switches between a high peak current and a low background current.

That peak current pinches off a spray transfer droplet and propels it towards the weld. The background current maintains the arc, but is too low for metal transfer to occur – ultimately helping control heat input and deposition.

• Older Pulsed MIG technology from 15-20 years ago was a significant improvement over conventional MIG, but manufacturers have since built new programs based on data sets specifically surrounding high nickel and chrome wires such as Inconel, further improving the process. Manufacturers can also work with individual companies to develop programs specific to their operation.

• Putting more decisions and controls in the operator’s hands: Inconel cladding applications vary from pipe to pipe and welder to welder. Each operator tends to dial in the systems differently to achieve dilution and puddle control as they see fit.

Older technology, however, limits the user to a fairly finite set of options. Newer technologies, such as the XMT® 350 MPa, offer a broader feature set that can be enabled or disabled to meet the operator’s individual preference.

These include adaptive Pulsed MIG welding, where the equipment automatically reacts to changes in the arc at higher processing speeds to maintain arc consistency; synergic Pulsed MIG welding where the operator can adjust pulsing parameters to account for changing weld conditions simply by adjusting wire feed speed on the feeder; and arc cone modification settings that give the operator the ability to make the cone wider (increased fluidity/flatter bead) or narrower (stiffer bead).

These can be turned on and off and mixed and matched to achieve the perfect welding conditions to ensure optimal deposition efficiency and dilution.