" ... Also out of curiosity if all this is true then why aren't AEB-L and friends used in plane blades and chisels at all? ...."
Because a plane iron has to keep the edge. You can't disassemble the plane and re-hone the blade every few cuts. Simple steels with high carbon, and a tad of tungsten/vanadium, are the usual suspects for plane blades. 1095, W2, Hitachi white, etc.
While AEB-L can achieve an edge approaching 3 microns, that isn't a very strong edge. This is why your razor blade only lasts a few shaves.
Lets use some large scale imagery to explain it. You have several materials to make a blade edge out of. One is made from concrete blocks, one from bricks, one from gravel, and ones from sand. The binder is mortar. The mortar is the steel, and the material is the carbides.
1) The concrete block blade edge will be very strong, but with the large joints ( grain boundaries), it will crack fairly easily. Also, the edge can not get very thin, as once you get it tapered to the size of a concrete block the blocks just fall out ... leaving a very rough edge. So, this is a very tough edge, but not a very high sharpness edge. It is difficult to re-sharpen this edge because it takes a lot of energy to shear away the concrete blocks and make a new edge. This is what the steels with lots of large carbide formers creates. D-2 or the high alloy super steels would be examples.
2) The brick blade will be stronger, because the joints are both stronger and smaller. The edge can get finer because the bricks are smaller than the concrete blocks, but still is limited to the size of the bricks. It is a bit easier to sharpen this blade, as the bricks are smaller and somewhat easier to remove in abrading. This is what most general knife steels are like. O-1, 52100, etc. would be like this.
3) The blade made from pebbles and small rocks will have a finer edge, but there is some tradeoff, and the joints between them ( grain boundaries) are not as well arranged nor tightly bound together. The edge will be the size of the pebbles. This is a great cutter, but not necessarily as strong, and the edge can be damaged fairly easily with abuse. This is a pretty easy edge to sharpen, but you have to take care not to damage it by making it too thin and having pieces of the matrix fall off. This is what whittling and culinary blades are like. Steels like 1095, W2. Hitachi white, etc. fit this category.
4) The blade with the sand and mortar make-up will have the finest edge possible. The size of the sand is the only restriction as to how thin you can shape it. But the tradeoff is that at that thinness and with the very small and weak joints between the sand, it will wear away fast ... and become a wider and duller blade. The good thing is that it is easy to abrade the sand back to a sharp edge. This is AEB-L. When you want the sharpest edge, but can tolerate the short edge life ... AEB-L is the steel you want.
So, as you can see, there is a place for AEB-L, but it is not the panacea for making knife blades. For blades that can be easily touched up regularly ( kitchen blades) it works well.
. I’m still rather amazed with just how well these steels preform. I also have to admit I’m a total sucker for impracticality sharp hyper polished edges. I know steels like m4 are monstrous preformers with toothy edges but hyper polished edges give me a certain sense of satisfaction and I love it when they stay that sharp for a while.
