Here's the old Crucible comparator.
https://www.crucible.com/eselector/general/generalpart6a.html
CPM M4 is more than twice as wear resistant as D2 while being 50% tougher.
IME (limited to a couple blades) D2 is too subject to chipping thin edges. (not tough enough) I have been satisfied that CPM M4 at Rc62 is tough enough and have not experienced "chippyness". For me that excluded CPM10V which has insane wear resistance, but only D2 toughness.
Going the other direction, CPM 3V is tougher than necessary at the expense of wear resistance, which is less than CPM M4
CPM 9V could be worth experimenting with - 50% more wear resistance than CPM M4 & almost double the toughness. Except those values are at RC 54.
People tend to think of "hardness" as the only quality of a knife edge, but it really has a very minor role in the attributes we actually need from that edge. An edge has to be hard enough that it does not bend when thinned to the geometry and applied to the work we want to do with it. Hardness is essentially a proxy for strength. (not directly wear resistance).
It is important for most practical woodworking tools that they be relatively easy to grind and especially to hone. I consider M2 relatively easy to grind. CPM M4 has the same grindability value. The value for straight M4 is aproximately 3.5 times lower.
https://www.crucible.com/eselector/general/generalpart5a.html
I chose (or impecuniousness forced
) me to not look at cutting materials that were less tough than D2. I would rather hone an iron that gets dull from wear, than one that is delicate and chips in difficult wood. But i would be happy to be funded to explore further.
I have several closely hoarded strips of tantung and it is my go-to material for tipping woodworking machine cutters. I have not gotten around to trying it as a plane iron. It might cover most of the bases, if you can make a thin edge without it chipping.
Richard, I prefer the soft shank welded to hard consumable edge. I "feel" (no experiments) that it adds a little to vibration damping. But the big factor is the convenience it provides to make hardened, un-machined blanks; which can be later machined to suit the plane they are needed for. There is a lot of value and economic efficiency in that model for a niche maker.
If this were resolved on a "production" basis, the savings over all HSS blanks is also significant. I was buying such small quantities (direct from Crucible) that I kind of doubt there was much price consideration, but if memory serves (it often doesn't
) the price for an approximately 2-1/4" wide x 1' long bar of 3/16" (the thinnest rolled plate available at the time) was around $90 - $120. I bought several bars at different times within approximately that range.
So the material would have cost about $80 for a 2-3/8" wide plane iron.
Or it could be cut either direction and yield bits for irons from 1/2" wide through a #8 jointer with 2-5/8" wide iron, and get maybe as many as a dozen bits. In my metric, A36 is practically free. So basic steel materials before welding gasses and filler rod was either approximately $80 per solid jack plane size blade, or approximately $10 per welded up version. And again, I have a faint feeling the welded up is "better".
Lately I tend to buy specialty steels from Hudson. Their prices on CPM M4 look good, but they don't list any thinner than 1/2" thick online. I'll try to remember to call them tomorrow and order some if they stock it thinner.
smt