Here is something from Teller Canyon Forge:
"5160, 52100 Steels
The vast majority of the non-damascus knives we make are made from new H-grade 5160 (a relatively clean chrome alloy spring steel) or E52100 (an aircraft-grade bearing steel). 5160 is also commonly used for automotive suspension springs, bumpers and floor pans. 52100 is frequently used to make cutting tools for non-ferrous materials. Good ball bearings are almost all made from 52100 while the not-so-good cheaper ones are frequently made from stainless steel.
One might, at this point, ask the question: Why aren't these steels used in making mass-produced knives whether by forging or stock-reduction? The reason 5160 and 52100 aren't (or at least shouldn't be) is that these steels only become superior knife steels when hammer-forged to shape. You can't just jam the stuff in a drop-forge or for that matter simply grind a blade from them and produce a really good quality knife. The steels only exhibit their truly outstanding qualities when forged to shape through multiple heat and forging cycles followed by multiple normalization cycles prior to differential heat treatment with three hardening and tempering cycles along with some sub-zero chilling at appropriate points in the process. The bottom line is that all of this is too labor-intensive for mass production to be practical.
Mass producers of knives don't have bladesmiths on their payrolls and stock removal doesn't involve forging and heat-cycling of the steel. The simple fact is that if you're going to mass-produce a product you want relatively few steps and little or no individual attention to each object being produced. Additionally, a desired result of mass production is relatively low product price. The process required to produce a really good knife from 5160 or 52100 is labor-intensive and not conducive to a low price."
Busse's heat treat is legendary, and may be even more involved than TCF's. When you buy a Swamp Rat, Scrap Yard, or Busse Combat, you are paying for the best knife blades in the industry. After nearly a year of testing Busse-made knives on very hard wood, I have never seriously damaged a blade.
