@not2sharp
There are a lot of modern steels that can run 60rc without significant loss of toughness and can even be tougher than other steels at 55hrc.
HRC will not tell you all the mechanical properties of a steel. Structures and features that make a steel tougher and more durable don't show up when testing HRC although there is a link between raw toughness and lower hardness just like higher hardness and wear resistance but on the chart you can also see the higher HRC doesn't always mean it more wear resistant. Carbide volume and type is significant.
An an extreme example of this effect but in opposite would be Rex121 at 55rc which will likely have lower impact toughness than 8670 at 60hrc due to the higher carbide volume dropping the impact toughness/shock resistance.
So if raw toughness is the ultimate goal I'd pick a steel that dumps the carbide volume, remove the less desirable features in the Microstructure with a bomber HT with solid time and temp selection and execution and you can rock 60rc all day for higher toughness operations given sufficient geometry.
The graphs in the article should show you that everything is a trade off and the wonderful complexity of it all. It never gets old, always more things to play with.
55rc is not realistic or desired for a quality cutting knife with a small thin blade.
55rc would limit the geometry since it's not strong enough to support a more desirable thinner geometry. The edge at 55rc will be more difficult to deburr, it will roll and blunt smooth faster in use. A small knife is also unlikely to be swung like an axe to see any benifit of the added shock resistance. Mostly folks just want an edge that doesn't chip and shock resistance isn't the only factor for that either.
I'd invest less in a specific HRC applied to ALL STEELS and invest more into understanding the features each steel can offer.
Lots of other cool articles to read on knifesteelnerds.com to build a solid foundation of knowledge if you want to go further down the rabbit hole.
-Shawn
That was an excellent read. My only question would be regarding the hardness target. Typical knife harness tends to be in the mid 50s(RC), especially for fixed blades. Was there any particular reason for testing at 60+, and would you expect a significant change in ranking performance if the test had targeted 55RC?
n2s