In simple terms,
Without temperature control It's just easy to make higher carbon plain steels more brittle and less strong at the same time.
Temperature Control is Carbon Control.
More Carbon means it needs more Temperature Control.
In detail,
Temperature controls how much carbon is put in solution and with 1095 there is enough carbon to cause problems if one doesn't have control of temperatures to manage it.
With 1095 and no control it's very easy to put too much carbon in solution or even not enough trying to avoid the pitfalls I'll get into below.
All this is important because its the level of carbon in solution can change the mechanical properties of the structure (martensite) that makes the steel hard after quenching and also how much of the previous structure (Austenite) will convert to the harder phase to make the steel hard after quenching.
Too much carbon in solution not only makes the harder structure more brittle (plate martensite) but can also "clog" up the transformation during quenching and there will be some leftover (Retained Austenite) unstable, soft areas hidden throughout the structure.
Another consequence of no temp control is one can dissolve all the carbides which will also make the grains blow up in size without carbides to pin them in place, larger grains means poor strength and toughness which is two fold.
So, having more carbon and less temperature control means it's easier to make less desirable features in the steel (larger grains, high retained austenite, plate martensite) which leads to a more brittle knife even at lower hardness.
There is nothing 1095 can offer that 80crv2,8670 or 1080,1084 can't do better when one is limited by temp control I feel.
Don't get me wrong,
with better temperature control ANY steel will have better consistency of features and performance.
I feel 1095 does offer some advantage with temp control over 1080 range stuff with being able to run harder, and have slightly more strength and more wear resistance but iron carbides are still the softest carbides so it's not ground breaking.
There are plenty of folks that run forge HT with no temp control on 1095 just fine but they could be getting a lot more performance out of the steel with better control. Same goes for any on the higher carbon simpler steel like 01, Cruforge V, 52100 etc.
Some folks just like the "1095" name and it's built a reputation no one questions and is more well known.
At the end of the day, if toughness is more desired than the lower carbon steels are superior for shock resistance and impact.
Personally, I use 1095 for thin slicers at high hardness.
Overall, these details are some of the many reasons why one person's HRC in the same steel can have different performance than the same HRC and steel on another persons knife.
It's the Microstructure.
I recommend
this book
by
@Larrin to dig deeper if curiosity takes you.
