I love this steel for big choppers and hatchets. It is basically 1070 carbon steel, with small additions of Vanadium, Molybden, Chromium, Nickel, and Silicon. The first three are intended to form some carbides for increased wear resistance (over the plain carbon steel), while Si and Ni are there mainly to improve toughness and ductility at high hardnesses, thus making this steel more resistant to impacts and more resistant to cracks, breaks, and chipping.
It is one of the very rare steels suitable to form and hold a decent edge, but which do not become brittle even at very low temperatures. Time ago I read a story about an exploratory team which needed to chop frozen meat in Antarctica, at -60 Celsius. At such temperatures, any material on earth becomes significantly more brittle than in normal conditions, including steel. They had all of the knives they had tried broken or badly chipped, all the way until a custom knife maker made them some knives out of L6 specifically for that purpose).
Gransfors Bruks uses a version of L6 in their axes and hatchets, as it is a very tough any easy to forge. My experience with their stuff is outstanding. It sharpens extremely easy to a shaving sharp edge and holds that edge very long in use (although not razor sharp). At 57 HRC, that edge can take direct rock impacts resulting in only plastic deformation and no chipping at all.
As it comes to knives intended to cut only, which are not necessary intended for impacts or heavy use, in this sort of application, L6 is mediocre to medium and you can find a lot of steels which highly outperform it.
Like someone mentioned above, one downside for L6 is also the fact that it is too permisive as a specification. The amounts of C, V, Cr, Mn, Ni, and Si have too wide ranges associated in the L6 specification, rather than a target fixed amount of each. This makes it possible that L6 from different sources to be so much different in properties from each other. I think this is one of the reasons why it is not too oftenly encountered in knives from reputable manufacturers (who prefer consistency). The heat treatment is also more complex and costly than in the case of plain carbon steel. For the cost of heat treating this steel in a way to properly form uniform carbide frome those elements (V, Mo, Cr), requiring deep cryogenic cycles, the manufacturers who have the tools to achieve that will rather prefer to do this with steels that offer better wear resistance and better corrosion resistance, at a close (even not equal) toughness.
PS: L6 was originally a bandsaw steel.
