S60V had been around longer than S90V and it was the first CPM stainless. So, naturally it gained a lot of attention. S90V eventually came out to replace S60V. I believe by then though factories had probably already made large purchases of S60V, so it was only wise to continue to market the alloy in their blades. Plus, I am unaware than S90V is available in large sheets like S60V. (Don't quote me on that last sentence though.)
S90V is more difficult to fabricate than S30V, more complex to heat treat for makers without proper equipment. So, in an effort to make these two primary tasks easier and cheaper, they dropped the alloy content essentially. Namely carbon and vanadium. It was marketed as a stainless 3V.
Something to keep in mind... When they lowered the carbon and vanadium content to essentially make S30V, it made a tougher end material in its intended function when compared to S90V. Makers liked that toughness. Even in pretty much all recommended heat treatments and hardnesses. To do this however, it takes a signifigant loss in wear resistance (compared to S90V). Corrosion resistance is still probably better on average than S90V, but not by a large margin and it will vary depending on heat treatment and finish. A negligible margin I feel. I use S90V as my exclusive stainless. I started using it after the S30V boom. I find it well engineered and very appropriate for the designs I make.
S30V has seen large popularity due to the fact that it is cheaper and easier to machine. For those who heat treat their own work, its austenitizing temps are within the limitations of their kilns and other heat treating equipment. Its also A LOT easier to finish in the hardened condition than S90V. Like day and night actually. Plus, its toughness is on the level and typically better than steels like ATS-34, 154-CM, BG-42, 440C etc. It can compete with some common tool steels as well, which is convenient for making large, hard use blades that need stainless properties. Like camping blades. It is ideal as the best 'balanced' material to most knifemakers. As far as all the aforementioned reasons. A good combination.
And yes, S90V will typically be tougher than S60V. Not by much, but it will be, with typical optimum heat treatments and hardnesses.
30=3,60=6,90=9... these are used as rough indications of comparitive wear resistance vales. The higher the better. They are also somewhat close to their respective vanadium percentage. Dual effect. Courtesy of Crucible.
-Jason
