N690 or N690Co as it is sometimes called, is a Cobalt-enriched stainless steel from Austrian steel company Bohler. N690 shares some similarities with it's other Cobalt-steel bretheren such as ATS-55 and VG-10. N690 is similar to a sophisticated 440C with better edge-holding and stain resistance. The steel is extremely fine grained. When it comes to edge-holding, it is agreed that the finer the steel grain, the better.

Chemical composition (nominal) %:
C 1.07, Co 1.5, Cr 17, Mn 0.4, Mo 1.1, Ni -, P -, Si 0.4, S -, W -, V 0.1

Various alloying elements (chromium, vanadium, phosphorous, manganese, molybdenum, nitrogen, etc.) used in blade steel, particularly in the family of corrosion-resistant “stainless,” produce certain desirable properties (edge retention, hardness, corrosion resistance, impact strength, etc.).

One of the most exotic alloying elements is cobalt, which is known to increase hardness and strength, as well as intensifying the effects of other elements in a particular steel formulation. Typically, N690 is hardened to a factor of Rockwell 58-60. Obviously, the key here is the addition of cobalt in the steel matrix. The cobalt allows the creation of a very uniform structure within the steel. When used in blade steel, this provides a fine and consistent edge, enhancing edge retention and sharpening receptivity.

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