SRS-15 - Japanese powder metallurgical (PM) steel. Excellent choice for kitchen knives. Ref - SRS-15 PM Steel Composition . Very high carbon content, and in combination with Tungsten and Vanadium this steel type gets a very high wear resistance. In general, this steel can be hardened to 64-65HRC without problems.
Haruyuki-Tsunehisa (formerly Akifusa) and Kagemitsu are one of the few producers making blades from SRS-15 steel.