DMT Aligner to sharpen, freehand stropping at a pretty consistent angle (very little apex deformation). I've tested M390 and gotten the same results from multiple companies, Benchmade, ZT, Kershaw, Steel Will, TRM, William Henry, Rike, and Kizer. S35VN I've had from even more companies, only WE and Factor Equipment gave me a properly lasting S35VN edge. None of the S35VN or M390 performed poorly, aside from the rather quick loss of razor edges, but M390 was the big disappointment for how long it will hold an edge overall. I like linear dulling, not some weird wavy pattern.
Grain size
- Simple explanation: Steel is made up of grains, smaller grains means greater toughness and strength. In depth: Smiths can vary heat treatment and forging processes to yield a finer grain size, though different steels are more easily heat treated for a finer grain size than others, this generally has to do with the alloy added, carbides "pin" the grain boundaries and prevent them from growing. The alloys with the highest melting point prevent grain growth the best. Vanadium and Niobium (Columbium) are often added to steels for finer grain. The reasons for grain size contributing to toughness and strength would require too much space to explain here. (Auth. Larrin Thomas)
ASTM definition of the Grain Size - The dimensions of the grains or crystals in a polycrystalline metal, exclusive of twinned regions and subgrains when present.
Strength
- Simple description: To resist deformation or rolling.
In depth: Strength is most greatly controlled by the Rockwell hardness scale, abbreviated Rc, though different steels can have different yield or tensile strength even with the same Rockwell hardness. The things that factor into this are grain size and alloy in solution. According to Takefu steel (the makers of VG-10) Cobalt strengthens the matrix of steel, regardless of Rockwell hardness. Carpenter steel offers tensile and yield strength numbers of their steels at various hardnesses and the variety of strength numbers while at the same hardness for different steels can be observed. Generally strength and toughness are opposed to each other, raising the hardness lowers toughness. Only decreasing grain size increases both strength and toughness. Higher strength means the edge can be thinner, because the edge is less prone to rolling.(Auth. Larrin Thomas)
Toughness
- Simple explanation: Ability to resist chipping or breakage.
In depth: Toughness is controlled by amount of carbon in solution, the hardness the steel is heat treated to, the carbide size and volume, and the other alloy in solution. High amounts of chromium weaken grain boundaries (though generally carbide size and volume is the limiting factor as far as toughness in stainless steels). Nickel and silicon in moderate amounts increase toughness without effecting strength. Carbide size and volume are probably the greatest controlling factor for toughness. (Auth. Larrin Thomas)
Wear Resistance
- Simple explanation: The ability to resist abrasive wear.
In depth: Important when slicing, especially when slicing abrasive materials like rope and cardboard. Wear resistance is important for edge holding in many types of knives, but less important in general when it comes to kitchen knives, because edge stability, strength, and toughness are more important for holding an acute, polished edge. If a cook uses a slicing cut and the edge is thick (compared to Japanese and other thin kitchen knives), then wear resistance is beneficial. Generally greater wear resistance means it is more difficult to sharpen, so even with a knife that will benefit from a steel of greater wear resistance, less wear resistance may be preferred for easier resharpening.(Auth. Larrin Thomas)
Edge Stability
- Simple explanation: Ability to hold a fine, acute, polished edge.
In depth: Edge stability is controlled most by carbide size and volume. The finer the carbide structure, the better a steel is at holding sharpness when sharpened very acutely and at a high polish. Evidences of a steel with low edge stability are losing initial sharpness quickly or chipping either while cutting or while sharpening with an acute bevel. The finer the edge and the finer the polish the more this will be apparent. Edge stability and toughness are often connected, but not always the same. Sometimes a steel can have high edge stability with fairly low toughness, or a steel with low edge stability can have moderate toughness. Blue Super has fairly high edge stability but low toughness; D2 has low edge stability but moderate toughness. Generally wear resistance and edge stability are opposed to each other since a greater volume of carbides means greater wear resistance but less toughness and edge stability, meaning one of the most important factors for selecting a steel are how much slicing it will be doing and how thick the edge will be. Usually edge stability is more important in kitchen knives.(Auth. Larrin Thomas)
Found this last bit to be rather interesting.
