Alan Williams makes this argument, based on metallographic analyses of a number of ulfberht swords. The two articles I linked are worth reading if you want to go deeper than the Nova documentary.

It's been a while since I've read his work, but I can offer a few comments. Hos work relies on a kethod called metallography where a sample is cut from the blade being studied, polished, and examined under a microscope. Iron forms crystaline structures, and these crystals vary in shape depending on the elements in the metal (like carbon) and the heating used in the forge. The crystal microstructures are what make steel harder than pure iron, and what make quenched and tempered steel harder and stronger than steel that's allowed to cool at room temperature. By observing these microstructures through a microscope, an archaeometallurgist can tell how the steel was manufactured and what physical properties the resulting object had.

Many of the ulfberht swords, as the nova documentary says, were made from steel that was manufactured using a different process than was common in western europe in the early middle ages, and the resulting product - crucible steel - was of a more consistent and reliable quality than the commonly available alternatives. Williams found, in his analysis, that the +Ulfberh+t swords were made with this superior steel, while many other swords (often labeled with +ulfberht+ and various other misspellings of the real workshop's name) were made by someone who lacked the superior materials (ie, they were cheap knock-offs).

This much all seems pretty clear from the analyses (though I should probably read them again, as it's been a few years). The next step in the argument is the piece that I find more suspect. The Nova documentary insists that crucible steel was imported from Asia, and generally dismisses western europe's ability to manufacture good steel. It's very possible (and Williams, in the first article i linked, argues for this idea) that someone in western Europe was trading for good steel from Asia. There was a lot of exchange moving through scandinavia between Frankia (where the genuine ulfberht swords were probably being made) and Baghdad, so it's not hard to imagine how wootz steel was able to cross so many thousands of miles.

I'm not convinced, however, that the technology was necessarily non-European. There's circumstantial evidence that some smiths were using bone ash to carburize iron into steel employing a process similar to that used to make crucible steel. It's possible that the workshop that made ulfberht swords perfected such a process, and didn't rely on imported metal. The Nova special turns the ulfberhts' crucible steel into a mystery that has to be solved (how were these swords made from metal centuries ahead of its time?!), but they may have simply been a technological experiment that worked but didn't catch on. Technological progress doesn't always follow a straight line, and some good ideas don't catch on in their time.

At all events, studies like the ones Williams did are really great. The metallographic tests do damage the artifacts (part of the sword has to be cut out with a saw), and as a result they don't happen as often as I would like. It's hard to convince museum curators to let you chop up a 1000 year old sword! But whe you do, the results can be very valuable.

I believe someone at York is working on an MA project about the Ulfberht swords. I haven't had a chance to meet this person yet, but I imagine it means we'll learn more soon!

Richard Furrer , the smith, has been doing research on Wootz for quite some time. He was a part of the Silk Road exhibition in Washington about ten years ago. Making and forging Wootz is a very time-consuming process ( you can't work it at a high heat, and it doesn't move much when you hit it) and , as he says, not at all certain. It is pretty amazing that he was able to pull off forging this sword.

Other than the closing of the Volga trade route, I'd like to know why such immensely costly swords couldn't have simply stopped getting enough buyers- wasn't it better, more effective, to spend, say, $500 on ten pretty-good swords for you and nine retainers than $500 on one good one for yourself, perhaps? There are other examples of high-value luxury work that changed. The laboriously cloisonne garnet-inlaid clasps and brooches, c. 7th century, also stopped being made, became simpler. ( I wouldn't dare suggest there was a connection between this and Wootz swords, only that markets for high-value items can change, for one reason or another)