Originally Posted by CliffordK

That one is listed as Chromoly. That would be either 4130 or 4140 steel. It should be a solid alloy, but it isn't as hard as can be. I'd hope most cassettes would be a version of chromoly, but I rarely see it specified, so perhaps not.

The SRAM Red
https://www.sram.com/en/sram/models/cs-xg-1190-a2

Is listed as being made out of heat-treated high grade tool steel. I don't see it listed on the 12 speed, but I assume it is similar. That is a big class of metals, but it has about twice the carbon content of the chromoly, and would be what would be used to cut chromoly. Heat treating is critical with a fine line between toughness and brittleness.