Westinghouse Bettis inconel electron beam weld cracking specification

The only welding code Tom knew of that allows cracks to pass spec — used to make the point that liquation cracking is so endemic to nickel-based alloys that the Navy nuclear parts code at Bettis tolerates millimeter-scale cracks within bounds. The thirty-percent-overlap electron beam weld procedure is cited as the context where the grain-boundary liquid film forms.

Okay, one of the things you need to know about nickel-based alloys — I told you a little bit about this the other day, when I mentioned the one welding code, out of Westinghouse Bettis, where they make Navy nuclear parts. They were welding some Inconels with electron beam welds, and that's the only code I ever knew of that would allow you to have cracks in your welds and pass the spec. There was a minimum size and a maximum size — I think it couldn't be more than about a millimeter in length. When you heat up these nickel-base alloys you get something called liquation cracking, which means it forms a liquid. I've talked about a Slurpee — you have solid crystals surrounded by liquid, and this stuff flows like a snow cone or Slurpee at high temperatures.

Eastern Massachusetts EB shop making pipe welds for Navy reactors in nickel-based alloys. The Bettis specification is "the first spec and the only spec I've ever seen in welding where cracks are allowed" — cracks permitted below ~1mm, justified by fracture mechanics. Tom was qualifying samples for six months; the shop kept failing the spec. Tom was kept out of the technical details due to lack of security clearance.

The only spec I've ever seen — and I had to try to qualify this for a company — I told you, for five years I did hundreds of failure analyses for a consulting engineering firm down south. There is a company in eastern Massachusetts that was making some pipe welds for Navy reactors, in these nickel-based alloys, and they're so prone to cracking that Bettis — Westinghouse Bettis, one of the Navy's two labs for reactor materials and design, along with General Electric KAPL [Knolls Atomic Power Lab] — they've been downsized a lot since they designed the reactors in the 50s and 60s, but they still exist. It's one of the two areas of the government where you still have competing labs, which is an expensive way to go.