Hypereutectoids

J

JamesBrock

Joined
Jun 4, 2013
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Need some insight:

I understand that quenching a hypereutectoid (W2 or 1095, for example) in too slow of a quenchant will obviously result in something less than optimal hardness, but is this actually detrimental to the integrity of the steel, or simply an overall reduction in Rc?

Thanks.
 
The reduction in hardness is due to forming structures other than martensite. The characteristics of a matrix contaminated with fine pearlite is not the same as a homogenous tempered martensite of the same hardness. One obvious flaw I've noticed is a reduction in fine edge stability.
 
01 is a hypereutectoid, as is 52100. These require a medium speed quench. All hypereutectoid steels are not the same.
 
Yes, but in the simple steels hypereutectoid are a fickle bunch.

So don't believe the charts, they're not specific to the steel you have in front of you. Within the definition 1095 it is possible to have a steel where the nose goes all the way over and touches the left hand side of the graph. So in some scenarios it is possible to have a steel that will form pearlite regardless of how fast you quench it. That may be true in W2 as well. Tricky stuff.
 
Not fully hardening would most likely cause edge rolling, or poor edge retention. Chipping is often the result of too thin of an edge, or too hard (too low tempering temperature.) Many of the alloying elements in O1 and 52100 are there to aid in grain refinement, carbide formation, and improve hardenability. Because of these elements, they are less likely to show a defined Hamon, but are more stable in quench. While it goes against common knowledge, the hypereuctoid steels MAY benefit from deep cooling/cryo to decrease retained austentite. I don't know enough to dismiss it, or fully agree, but from what I have read its a good possibility that it can work.
 
A lot of great information.

So then, using 52100, for instance, I could actually forego the Parks 50 and obtain homogenous martensite with a slower oil?
 
You would need to look up the specifics. Parks 50 is hard to find in my area. I have a Maxima oil that is faster than parks 50. I did O1 and 1084 in the Maxima oil, and they turned out great. I am doing a 52100 knife right now, and am considering professional heat treat because of the grain refining cycles, and soak needed to get the most from it (with possible cryo.) 52100 is a very high carbon steel with specific soak temps and times, and may benefit from cryo, so experiment and see what works. O1 can be quenched in canola oil if the heat treat is done right (canola at 120f for quench.)
 
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