[jimmontg]

Hi everybody I was going through some old notes from my machine shop heat treat/TIG welder days. I also did some extra research for some actual science versus anecdotal stories. Thought I put a few things out there.

tribology, tribological
"Tribology is a branch of mechanical engineering and materials science. Tribology is the science and engineering of interacting surfaces in relative motion. It includes the study and application of the principles of friction, lubrication and wear. In knifemaking, tribological studies play a role in determining steel wear characteristics and this is the only scientific, accepted method to determine the relative wear resistance of steel. Cutting tests do not; they are too variable, and knife blades can not be consistently created to any high degree of accuracy. In tribological testing, wear surfaces, indentation, loss of mass, and friction are all considered and calculated. This is ASTM and AISI approved testing of the wear resistance of steels and it is the only recognized standard."

O1: This high alloy oil-hardening tool steel is a standard in the industry for a reason. It's a great hyper-eutectoid tool steel with about .9% carbon and the version I use has high tungsten and vanadium with a bit of chromium, though not enough to be stainless steel. I use it when clients want a great performing black colored blade, because the finish and bluing is excellent on this steel. On one website about steels used in woodworker's tools, the writer claims that because O1 has a higher martensitic conversion than other steels, cryogenic treatment is not effective. This is flat-out wrong. While O1 does perform well with conventional heat treating, cryogenic treatment vastly improves this performance. How does it benefit from cryogenic treatment? O-1 can have up to 8.5% retained austenite when quenched to room temperature (20?C). While this does not seem to be a lot, it is significant, and proves that at the very least, O1 should be quenched to sub-zero temps and held there to reduce the amount of retained austenite. So much for the woodworker's assessment of O1. Now here's the really important result and proven by highly specific and controlled technical scientific studies: in treating O1 to shallow cryogenic treatment (SCryo), the wear resistance was improved 221%. In treating O1 to deep cryogenic treatments (DCryo), the wear resistance was improved 418%. Simply put, either of these treatments dramatically and substantially improves the wear resistance while making the blade tougher, and the finish better overall! Why not do this?

I came across this. I never knew the name of the science of cutting basically. I found a wealth of information on carbide formation. I also now know the scientific reason I alway shallow cryo my O1, ie pack in dry ice until it evaporates with my homemade ice chest it takes almost 3 days. It definitely makes a difference as measured scientifically. It held an edge longer, but I couldn't say about toughness as I tell my customers it isn't a pry bar. Leastways I haven't had one come back because it broke. Liquid nitrogen Deep Cryo improves it even more and that's just O1. D2 is through the roof with both types especially with LN cryo. I have to get after my heat treating company, guy told me my steel only needed 2 hours, but it needs at least 6 in LN for 154cm and same for 440C, actually all high chrome knife steel.

I got most of this stuff from Jay Fisher's Knifemaker website.

Just some food for thought. Here's a few references. There's much more than this though.

Cryogenic Quenching of Steel Revisited, Zbigniew Zureki, 2005

Cryogenic Treatment and its Effect on Tool Steel, Yugandhar, Krishnan, Rao, Kalidas,

Effect of Deep Cryogenic Treatment on the Carbide Precipitation and Tribological Behavior of D2 Steel, Das, Dutta, Topo, and Ray, 2007

Comparison of Wear Properties of Tool Steels AISI D2 and O1 With the Same Hardness, Bourithis, Papadimitriou, Sideris, Tribology International 39 (2006)