... I see references on the forum to HC steels are fine on soft materials if you do not mind a dull blade for long term cutting...
I have come to the conclusion that some of the differences of opinion regarding high carbide steel relates to how "sharp" is defined.
I know that seems silly, but I think that my "sharp" is somebody else's "dull".
There seems to be a base assumption by such folk that a low-grit edge for abrasive cutting (what HC steels excel at) is
already "dull" and unusable for harder materials/use like carving wood (e.g. planar blades) or for delicate push-cutting like shaving or surgery. The lateral stresses inherent in carving hard materials call for a more refined high-grit edge and also a thicker apex-angle for a stable geometry that would not be preferred in abrasive cutting and shaving. In razor-blades the goal is a
very thin very polished and refined apex that would not well withstand the lateral stresses of carving nor abrasive cutting.
The thing is, the low-grit edge for abrasive-cutting is "sharper" than the refined edge sharpened to the same angle because the low-grit edge has "teeth" that penetrate more easily than a high-grit edge, focusing cutting-force onto a smaller area. And the low-grit edge retains this "toothed" profile through more abrasive cuts than the "un-toothed" edge that smooths out. But the low-grit edge does not push-cut as well as the high-grit edge because the teeth have rough ("dull" less acute) spots between them where material can pile up on a push, and the teeth can gouge into the material being cut and experience lateral stress that bends/breaks them as they lack support from material at their sides. Thus push-cutting with a plain-edge evinces higher apparent sharpness and durability at the same apex angle,
regardless of high- or low-carbide.
Low-grit vs high-grit is a matter of sharpening/finishing, not a matter of steel-type.
"Sharp" should refer to average apex diameter along the edge. Low-carbide steel (<10% carbide) can achieve an average apex-diameter (at best) ~0.5um. It is limited by the hardness of the matrix, carbides+binder. A tungsten-carbide or diamond microtome blade (>80% carbide) can achieve an apex diameter ~0.005um,
100X sharper, due to its superior hardness. High-carbide steel (>10% carbide) can achieve a blade
sharper than a low-carbide blade through shaping carbides at the apex, but the difference should be imperceptible to a user as the percentage of carbides
in the apex isn't really all that different. In abrasive cutting, the high-carbide steel holds this sharp edge
longer than a low-carbide blade as those carbides function as plates to prevent the binder (which stabilizes the edge) from being abraded away, whether the edge is finished to a high-grit or a low-grit. In non-abrasive cutting of soft materials (e.g. food), high-carbide steel can take the same level of edge refinement as a low-carbide steel, it just requires better (sharper/harder) sharpening equipment, and it will hold that edge just as well as low-carbide steels. Now if you start testing impact or lateral strength at very thin geometries (e.g. <12-dps) carving hard materials, you might notice that higher carbide leads to lower fracture-toughness, but I have doubts about the significance of such tests in common use of knives since the impact-toughness threshold is fairly low for most steels at knife-hardness levels (20-50J compared to >150J in steels like S7), and the threshold edge-angle for avoiding chipping in planar blades is ~15-dps. Geometry is the dominating factor
The assertion of taking a "dull" edge and holding it forever is founded on either poorly prepared steel or poor sharpening equipment/technique. Depending on one's use, one could certainly get-by with 420HC or 440A or 13C26 or even 1084 or 1075, and those are much cheaper, but they are not "sharper" than a high-carbide steel like S110V, they are just easier to HT and to grind to a high-grit polished edge. They also dull quickly.
