Welding Tips and Tricks

I am going to take a welding certification test in a couple of weeks at an aircraft engine repair station that overhauls thrust reversers . The Test is on .032" Inconel . Butt joint and Tee joint.
Butt joint is flat and t joint is horizontal. I need this job. What are some tips to help me pass? what can i expect?
I have welded stainless steel but not inconel. What is the difference?

Inconel alloys are oxidation and corrosion resistant materials well suited for service in extreme environments. When heated, Inconel forms a thick, stable, passivating oxide layer protecting the surface from further attack.

Inconel can be welded using conventional stainless steel TIG welding techniques. Inconel Filler Metal 625 rod is used to weld Inconel to Inconel as well as to dissimilar metals including stainless steel. Inconel weldments are high strength and are highly resistant to corrosion and oxidation. Many welders describe that welding Inconel as "dirty". In other words, the weld pool appears to be under a "skin" and is not well defined. In addition, the weld pool is somewhat "sluggish" as compared with steel or stainless steel. These characteristics tend to result in a "coarse" appearing weldment as compared to stainless steel. Welding Inconel is not necessarily more difficult to weld than stainless, just different.

Good answer there romij,

inconel 718 and a few others actually contain a bit of aluminum content to allow heat treatment strengthening. that little 1 percent or so of aluminum really makes the puddle sluggish...especially if you ever let the hot tip of your rod get outside the argon shielding coming out of the cup. Using a bigger cup helps too by giving you a bigger argon sheild area.
Inconel takes about 2/3 the amperage to weld than the average stainless steel. Its a nickel alloy and a poor conductor of heat.
It is also succeptible to crater cracks if you taper amperage too quickly. I have found that tapering amperage while continuing to move the torch helps prevent crater cracks.

Jody aka Admin

I think romij forgot to site his sources...

"Inconel alloys are oxidation and corrosion resistant materials well suited for service in extreme environments. When heated, Inconel forms a thick, stable, passivating oxide layer protecting the surface from further attack."

Taken from Wikipedia, under properties.

"Inconel 625 can be welded using conventional stainless steel TIG welding techniques. Inconel Filler Metal 625 rod is used to weld Inconel to Inconel as well as to dissimilar metals including stainless steel. Inconel weldments are high strength and are highly resistant to corrosion and oxidation. Many welders describe that welding Inconel as "dirty". In other words, the weld pool appears to be under a "skin" and is not well defined. In addition, the weld pool is somewhat "sluggish" as compared with steel or stainless steel. These characteristics tend to result in a "coarse" appearing weldment as compared to stainless steel. Welding Inconel is not necessarily more difficult to weld than stainless, just different. By following the welding procedures outlined in the header construction tips article, successful welds with Inconel 625 are possible."

Is taken from
http://www.burnsstainless.com/TechArtic ... ticle.html
the last paragraph.

I love google.