Repair welding Inconel 718 with Hastelloy W?

[KirbyWan]

Howdy all,

I'm designing a repair for an Inconel 718 skin ~.070 thick with a crack in it. It is right next to a brazed doubler and the welder is worried about the braze metal contaminating the weld joint. He recommended using Hastelloy W weld filler metal instead of 718 to prevent any problems incase the braze metal mixes with the weld pool. I have looked around, but can not find any reference that says Hastelloy W is a valid filler wire for welding Inconel 718. Can anyone provide a reference or talk about Hastelloy W's compatability with precipitation hardenable Inconels? I'll be doing a precipitation heat treatment then an age heat treatment after welding as a stress relief.

Thanks,

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.

 

[unclesyd]

Here are two brochures from Haynes concerning Inco 718 and Hastelloy W. The 718 brochure has some information on welding with Hastelloy S or W. I would definately give Haynes a call. Make sure your welder uses a dressed Tungsten and uses a short arc

http://www.haynesintl.com/pdf/h3017.pdf

http://www.haynesintl.com/pdf/h3055.pdf

 

[metengr]

If you have not done so already, make sure you qualify a welding procedure for this repair.

 

[KirbyWan]

metengr,

I don't usually go outside of the manual in a welding repair, (and by I, I mean our very experienced welder, I'm just an engineer.) could you describe what is involved in qualifying a welding procedure? For what I'm doing I'm following the welding procedure in a manual, but making changes because the crack is beyond the limits in the manual. It was cracked and previously repaired, then cracked again, I think because they did not do a stress relief. I'm adding the stress relief and swithcing the filler wire from 718 to Hastelloy W.

unclesyd,

Great information. That was what i was looking for. I wanted to make sure that the two metals were compatible in a weld.

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.

 

[boo1]

While you did not indicate what industry you in,from your title I assume we can discuss, Aerospace industry.

AWS D17.1 Specification for Fusion Welding Aerospace Applications

The Engineering Authority shall design the weldement and define the requrements. Performance and procedure qualifications must be maintained. Welding processes are developed to ensure quality welds. Two of the critical elements to the weld procedure are base metals and filler rods. These assignments have been based on comparable base metal characteristics, such as: Composition, Weldability, Mechanical Properties. Indiscriminant substitution of materials in a set of welding rod Group Numbers may lead to problems or potentially failures.

Hastelloy W metal is in group IIIA
Inconel 718 metal is in group IIIB

Engineering assessment is necessary prior to a change in materials, joint requalification is required.

 

[KirbyWan]

boo1,

So what goes into requalifying a joint? Is there a standard set of tests that I can run on a set of weld specimens? Is this going to require a fatige study? I'm still a fairly new engineer, and havent' done a weld requalification before.

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.

 

[metengr]

Review AWS D17.1.

 

[boo1]

FFA certificate number F8WR457X, Limited Rating for Welding requires you to follow AWS D17-1 and The Limitations are: "Use the methods, techniques and practices prescribed in the current manufactures maintaince manual or Instructions for Continued Airworthiness, or other methods and practices acceptable to the Administrator."

To deviate from the approved weld procedure, you must both qualify the new weld procedure (test coupons) and sign off on the deviation (analysis). Refer to Advisory Circular 00-56, ASA 100 Standard and your Quality Assurance Program.

As the agent of the certificate holder are you the authorized design agent for the part or a repair depot?

 

[KirbyWan]

I'll check out the Advisory Circular and look at AWS d17.1 again. I'm not sure what the authorized design agent is. We work with an independent DER.

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.

 

[Duwe6]

Further note: make d@mn sure that the crack has been *fully* removed prior to attempting any welding. Usually the welder quits grinding when he can no longer see the crack. Because of the tiny size of cracks, this leaves both ends left in the basemetal, guaranteeing that the crack will reappear. Use red, visible Dye Penn - PT - to track the crack. After PT, start grinding. Redevelop the area during each stop in grinding. Keep grinding until all the *red* is gone. It will take going farther and deeper than you were able to see prior to the PT. *Now* the welder is ready to start with the repair weld.

 

[KirbyWan]

I use the boeing procedure for stop drilling cracks. We use florescent dye pen to mark the crack tip, then drill beyond the crack tip to catch the edge of the crack with the diameter of the drill bit. That way we know we have captured the end of the crack. After that we go back and pin route the crack before welding.

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.

 

[boo1]

Working under an independent DER you are not the authorized design agent. It's not that your process will not work, its that changing the filler metal (filler is a critical element of the weld process), you are not following the weld process.

Devations from approved repair procedures, opens both you and your employer to legal liabilty .