Is there a good reason that 203E is not mentioned or used much in pattern welded steel these days.
I have looked around, and there seems to be no ready source...
Do any of you old timers have any thoughts about this??
Yeah, 203e has very little carbon and about 3% nickel, while 15n20 has about .7% carbon and 2% nickel. Theoretically, the 203e should be a bit brighter in the etch than 15n20, but 15n20 will hold an edge and the 203e will not... I've used it recently in some composite blades where it was nowhere near the edge, mostly as an experiment to see how it looked. As the paper KenH linked says, if you mix it with a high carbon steel and fold it a few times the carbon content will equalize through the blade. This cannot be said for pure nickel, which some people use in damascus.
203E was all the rage "back in the day", before we discovered 15N20. As has been mentioned, its very low carbon, hence non-hardening. Once makers started finiding sources for 15N20, 203E quickly went by the wayside.