What is tougher?

[ZMW]

Cool info, I appreciate it. It would be fun to see more steels on that toughness chart for comparison. The Powder metallurgy process is the same that makes PS27 tougher then ingot D2 - is that right?

[Pelagic]

Spyderco's k390 is ran at a lower hardness than their Rex45 which could be the determining factor.

[JacksonKnives]

Cool info, I appreciate it. It would be fun to see more steels on that toughness chart for comparison. The Powder metallurgy process is the same that makes PS27 tougher then ingot D2 - is that right?

Correct. Larrin analyses some tests of cast vs PM D2 equivalents in the middle of the page here: https://knifesteelnerds.com/2018/05/28/ ... -of-edges/

It's not magic or anything; high carbide volume still allows more crack propogation than low carbide volume.

In some scenarios (large cracks already present, in the tests Larrin analyses they're looking at shearing dies) the conventional D2 is actually tougher.

The big carbides are a part of what some people love about D2 edges, so as always YMMV.

[ZMW]

Cool info, I appreciate it. It would be fun to see more steels on that toughness chart for comparison. The Powder metallurgy process is the same that makes PS27 tougher then ingot D2 - is that right?

Correct. Larrin analyses some tests of cast vs PM D2 equivalents in the middle of the page here: https://knifesteelnerds.com/2018/05/28/ ... -of-edges/

It's not magic or anything; high carbide volume still allows more crack propogation than low carbide volume.

In some scenarios (large cracks already present, in the tests Larrin analyses they're looking at shearing dies) the conventional D2 is actually tougher.

The big carbides are a part of what some people love about D2 edges, so as always YMMV.

Wow - that is some awesome research! It is amazing how metallurgy is its own in depth science, and that your average person has zero idea about the subject

[xceptnl]

I don't have enough use to compare yet, but I have not seen a noticeable difference (no chipping or deformation) when comparing K390 to HAP-40. This use did include some woodcarving with lateral edge stresses, but no knots to speak of.

[jpm2]

I don't have enough use to compare yet, but I have not seen a noticeable difference (no chipping or deformation) when comparing K390 to HAP-40. This use did include some woodcarving with lateral edge stresses, but no knots to speak of.

Speaking of Spyderco k390 and hap40, k390 takes slightly less damage than hap40. Again when I speak of damage, I'm referring to either rolling or chipping. In this case, hap40 rolls slightly before k390 chips or rolls with equal force. k390 also has significant more wear resistance.

There's no comparison between Spyderco's hap40 and rex45 when it comes to edge damage or wear resistance, even though they are almost equal composition, rex45 is superior in all aspects. The heat treat makes all the difference. hap40 could be what rex45 is, but isn't it's current Spyderco form.

[JacksonKnives]

The difference that can be made with a targeted heat treat are pretty amazing.

I don't doubt that the team in Seki had access to great resources (including Hitachi's input on what's best), but it doesn't entirely surprise me if Golden has tweaked things a little bit more, or that their standards line up with ours more closely.

Tradition and authority play a funny role in the manufacturing process. You don't want a factory boss who is just making it up as he goes along, or worse, just following whatever whims come from a design team without checking against his own standards.