Inconel 625 overlay on 8630 Forging blasted using alumin oxi

By davidanewton Date 11-05-2013 23:05

ALL, My Inspector tells me that a forging has been blasted using Aluminum Oxide. This has turned the 8630 material forging gray. I had see this some months ago. The part is in a part of the world that has extremely high humidity. It has not rusted. The part's ring grooves are now going to be clad using Inconel 625. The Contractor tells me that there is no problem cladding over the Aluminum Oxide finish. I have found papers on line that say it is a problem and some that say it is not a problem. I would like a definite answer one way or another if any of you have experience with this. My recommendation is to blast the areas to be clad using steel shot and grit, garnet, silica or black beauty to bring the steel to a near white finish and clad over that. I don't know how the Aluminum oxide interacts with the Inconel 625 and 8630 forging material. Maybe it can cause detrimental inclusions, lack of fusion? I just don't know but it would be great to hear your thoughts, experiences and credentials.

Thanks and I look forward to reading your replies.
Dave Newton

By cddolan74 (**)

Date 11-06-2013 12:17

What welding process and gas are you using

By MMyers

Date 11-08-2013 19:36

I think you'll get increased surface oxide formation on the 625. Whether it will be significant enough to produce LoF or inclusions is really up in the air given the number of variables (process, gas, procedure, ring groove design), but I agree with you, it'd be better to eliminate the possibility as opposed to fight a weld the entire time or produce a defective part.

Credentials? Oh, not much. I'm a professional button pusher and certified coffee drinker.

By 803056

Date 11-08-2013 21:26

Aluminum oxide has a high melting temperature; on the order of 3200 to 3600 degrees F. That is well above the melting temperature of nickel (2700 degrees F [rounded]) and many of its alloys. It seems plausible that the aluminum oxides could remain as solids during the welding process. If it does not form a barrier between the casting's surface and the nickel overlay, it could manifest as inclusions in the solidified overlay.

Credentials: spiffy dancer and sharp dresser.

Best regards - Al

By cddolan74 (**)

Date 11-11-2013 14:04

Dave,
Al is correct on the possibilties of these AlO becoming inclusions. the oxides being a lighter density than nickel will float on the surface of the weld pool. and when they collect togeather will form big black spots on the surface or can be pulled down becoming an inclusion. I asked what welding process and gas covering cause this will make a diffrence in that outcome. Then again better safe than sorry and would most likely remove AlO.

By Lawrence (*****)

Date 11-12-2013 18:09 Edited 11-12-2013 18:43

Pratt Whitney, General Electric, Allison, Rolls Royce standard practice manuals have all at one time or another, recommend aluminum oxide grit blasting for part cleaning on superalloys such as Inco 625, the Hastalloy's, Rene 41 and others both precipitation hardenable and non.

My experience is primarily in aerospace, with a little in turbines. Inco 625 and Inco 718 are both typical in hot sections that often require build-up or crack repair.

I'm not endorsing the method above all others mentioned... Just relating past experience

I don't believe the "grey" surface you see on your casting is smeared aluminum/oxide on your part. But you could always follow blasting with the hot zone getting extra prep via a carbide burr or silicon carbide disc/flapper

As others have mentioned, process variables may come into play... Also of course the amount of area you need prepped will factor in.

Aluminum oxide, along with it's high melting temp.. Is almost as hard as diamonds... Which is why it is such an excellent blast media.

Edit:
http://www.nickelinstitute.org/~/Media/Files/TechnicalLiterature/GuidelinesfortheWeldedFabricationofNickelAlloysforCorrosion_ResistantService_11012_.pdf

http://www.twi.co.uk/technical-knowledge/job-knowledge/welding-of-nickel-alloys-part-1-107/

http://www.haynesintl.com/pdf/h3073.pdf