I'm still curious about Vanadis 4 extra Superclean. ZT is putting it out there, and the data sheets are available, but no one seems to know much about a steel that Bohler itself says is great for knives because it balances the toughness of 3v with the edge retention of M390. Surprises me.
http://www.uddeholm.com/knife_steel.htm
"Other knife steel grades
Receommended steel grades for hand knives
Uddeholm Vanadis 4 Extra
This is a PM tool steel grade designed for maximum toughness and is recommended for use in tactical utility knifes, where a high reliability is needed. Although it can be hardened to 64 HRC, the recommended hardness range is 58-62 HRC.
Uddeholm Vanadis 4 Extra.pdf
Uddeholm Vanadis 23
A PM high speed steel, similar to PM M4. It is the right choice for knifes demanding maximum hardness and high wear resistance, as a hardness of 66 HRC can be attained.
Uddeholm Vanadis 23.pdf
Uddeholm Vanadis 10
Very high alloy content with 10% vanadium and a hardness of 60-66 HRC makes this our most wear resistant PM grade. It is suitable for knives n prolonged (professional) use in abrasive environments, where the demand on toughness is not predominant.
Uddeholm Vanadis 10.pdf
Uddeholm Sleipner
Uddeholm's modern version of the classic D2 tool steel, with improved toughness to better fit active knife use. Even though this is not a PM steel, the finer steel structure in Uddeholm Sleipner gives better machinabilty, polishabilty and edge retention. The hardness range is 58-64 HRC."