One problem with forging 154 CM is the air hardening when it cools.
I have read some of Wayne Goddards writing and he sends the stainless alloys to Paul Bos for heat treating.
154 CM and others, such as D2, ATS 34, and 440C have a tendency to decarbonize when heated in a standard furnace. That is the reason these steels are heat treated in a vacuum or controled atmosphere furnace.
Heating in a forge would be exposing the steel to the atmosphere, and the contact with the Oxygen in the air could cause it to decarborize, which, in my opinion would cause the steel to be worthless as a cutting tool. I don't know if it could be hardened if it decarborized very much.
But, that might depend on the depth of decarborizing. If the decarborized depth is shallow, then the blade could be ground down after forging, removing the decarborized skin, unless it decarborized all the way through. But then, it would have to be annealed, stress relieved, then heat treated in a controlled atmosphere or vacuum furnace if it only surface decarborized.
That is one reason why forgers prefer steels like 52100, 01, W2, 1095 because they can be heat treated with a torch or in a forge. Apparently steels in this class do not decarbonize when exposed to oxygen when heated.
Some people do make layered stainless steel blades, but I don't know anything about how they prevent the stainless from decarbonizing. It is possible they let it decarbonize anyway, or use something like 303 stainless and layer it with 01, 52100, or one of the other carbon steels to get the layers or carbon and heat treatable steel.
My opinion, and I don't have a way to prove it, is that 154 CM and other stainless steels will slightly decarborize even when heat treated in a controled atmosphere furnace. This would be only a surface decarborization to a shallow depth.
I base this on the fact that most of my blades do not hold an edge very well on their first sharpening. They seem to hold an edge much better when some of the outside is ground or sharpened away.
Even blades that are very sharp initially will show a slight dulling even if they are not used. This could be from the lack of carbon, and formation of rust on the finely sharpened edge.
