The steel used in most US-made Kershaws is Sandvik 14C28N. This is very likely the steel you're thinking of, and the owner of knifesteelnerds.com rated it as his favorite budget steel[0]. It has extremely high toughness (resistance to chipping/breaking) and a fine grain structure that allows it to take a very sharp edge without microscopic rolling/chipping. Some other steels are used, including 420HC on low-end models, CPM154 on automatics, and several steels commonly found on more expensive knives in special editions.
Chinese Kershaws usually use 8Cr13MoV, and don't put much effort into heat treatment. Some use D2, which is semi-stainless, somewhat hard to sharpen, and low-toughness (it chips easily), but high in wear resistance. Some low-end models use even cheaper steels.
[0] https://knifesteelnerds.com/2020/06/15/what-is-the-best-budg...
Kershaw's lower end line are often full of really cheap Chinese steels. Same with CRKT.
I've taken a "buy good knives" stance. My favorite is definitely not cheap, but it gets a ton of carry time. I'd also hate myself if I lost it lol
But if you're the type to carry a knife, a good knife goes a long way and getting a knife steel on it that can last is also a good way to go. Modern super steels are insane.
The company that owns Kershaw also owns Zero Tolerance, which is a higher end brand. They use steels like S35VN and 20CV, which are fairly high end steels. 20CV is roughly equivalent to M390.
Not many steels sharpen really easily and stay sharp long. Usually you lose edge retention for ease of sharpening. M390 and 20CV are hard to sharpen but hold an edge really well.
My personal favorite is M4, it has superb edge retention, is tough to sharpen, but isn't as stainless so is often coated to prevent rust. Definitely my favorite though. It's just a joy to use.
Like many makers, they use many different steels across their collection, so you'll need to be more specific. See: https://kershaw.kaiusa.com/blade-steels
I had an S30V leek I got from CK& T and carried for many years that I eventually lost to airport severity.
I wouldn't call S30V easy to sharpen though.
Anyone happen to know where they're sourced from?