Are CPM ( Powder Steels ) More prone to chipping?

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Steel130

Steel130

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I have heard some talk that powder steels such as CPM154 and S30V ect. are more prone to chipping? I thoughthat were powdered because this gave them a finer grain structure thus making them stronger? I am trying to get into a little more of the metallurgy side of things as well. So are powdered steels stronger as in being able to take more load on the edge and lateral pressure and highly wear resistant due to the larger amount of carbides in them, but not as tough?
 
All else being equal, the PM version of a given steel -- for instance, CPM-154 versus 154CM or CPM-M4 versus M4 -- should be less prone to chipping for the reason you mentioned (finer grain structure).
 
Some of the confusion comes from anecdotal complaints. People who unwittingly abuse the edge and think it's the steel or the heat treat at fault. Or sometimes the heat treat IS at fault, not the steel.
 
Esav Benyamin said:
Some of the confusion comes from anecdotal complaints. People who unwittingly abuse the edge and think it's the steel or the heat treat at fault. Or sometimes the heat treat IS at fault, not the steel.
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^ +1.

all the conditions/factors must be taken into account. here's one example, some people kept saying ZDP-189 was "chippy" and prone to chipping. i took one of my knives in ZDP and did some metal cutting with it and it held up very well. turns out, one of the people complaining about chipping set their knife's edge bevel to less than 10 degrees per side, which caused their results.
 
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Has more to do with the heat treatment and tempering process.
 
Steel130 said:
I have heard some talk that powder steels such as CPM154 and S30V ect. are more prone to chipping? I thoughthat were powdered because this gave them a finer grain structure thus making them stronger?
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Fine carbide structure doesn't automatically equate to tough. It allows a given area to be more carbide-rich.

Steel130 said:
...are powdered steels stronger as in being able to take more load on the edge and lateral pressure...
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Charpy results are not formulated by lateral flexing(sideways bending). Powder steels will not flex and return to true like ingot steels can. They will shear.

Steel130 said:
...and highly wear resistant due to the larger amount of carbides in them, but not as tough?
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Carbide volume doesn't automatically reflect wear reisistance. A lower volume of harder carbides(V, for example) may prove more wear resistant than a larger volume of softer carbides(Cr, for example).
Carbide type, carbide volume, and the heat treat will ultimately determine wear resistance and toughness.
 
Powder steels seem easier to sharpen ( say a DMT diafold, for instance) than their ingot steel counterparts of similar composition and hardness. Is it my imagination or is it a real thing? I don't recall ever seeing the claim made by a steel company or knife manufacturer.

154cm vs CPM 154 both @ or around rc 59-60

and....

D2 vs. CPM D2 Both @ or around RC 62

These are the ones I have the most experience with and are closest in hardness figures claimed ( not tested by me) by manufacturers.

?

Joe
 
Buck_110 said:
Powder steels will not flex and return to true like ingot steels can. They will shear.
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Steel flexes within the elastic range, no matter the composition, no matter the production method, no matter the hardness. You go beyond the elastic range, and then it bends or fractures. The amount of load to reach this transition is where the differences in alloy, dimension, and composition lies, but all steel can flex.
 
All I know is, I found bigger chips on softer 154CM steel at Rc 57-59(Emerson CQC-7) than I did on CPM-154(Galyean Pro Turbulence) at Rc 60-62 when I accidentally ran the edge onto metal. Also found that M390 at Rc 62 still tends to roll rather than chip on thick cardboard. So I suppose fine grain structure is a plus to toughness.
 
hardheart said:
Steel flexes within the elastic range, no matter the composition, no matter the production method, no matter the hardness. You go beyond the elastic range, and then it bends or fractures. The amount of load to reach this transition is where the differences in alloy, dimension, and composition lies, but all steel can flex.
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True. The range of powder steel is much more narrow, though.
 
Noctis3880 said:
All I know is, I found bigger chips on softer 154CM steel at Rc 57-59(Emerson CQC-7) than I did on CPM-154(Galyean Pro Turbulence) at Rc 60-62 when I accidentally ran the edge onto metal. Also found that M390 at Rc 62 still tends to roll rather than chip on thick cardboard. So I suppose fine grain structure is a plus to toughness.
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How so?
Is it really a surprise that metal taxed the edge more than cardboard?
 
Fine grain structure is a plus because reducing grain size increases the stress needed to allow dislocations to cross the grain boundary. This increases the yield strength. A crack changes orientation at a grain boundary, so many small boundaries resists crack propagation by deflecting the cleavage from whatever plane it is on.
 
The finer the grain size the tougher the steel ! Don't confuse grain size with carbide size !!
Powder steels have substantially higher transverse impact strength ! Toughness means impact strength.
Powder steels ARE easier to sharpen.
 
The more even distribution of the carbides helps the PM steels as well. Having carbides clump up in strings or whatever makes for a chippier blade.
 
mete said:
Powder steels have substantially higher transverse impact strength ! Toughness means impact strength.
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If this is the case, then why are turbine engine blades, firearm barrels/chambers, revolver cylinders, railroad tracks, vital pieces of infrastructure, etc. produced from ingot steel?

While Charpy test results may look impressive on paper, how well do they really represent real-world scenarios? Until skyscrapers are erected with powder steel I beams and aircraft carriers hulls are constructed from powder steel, I am personally not convinced.
 
Buck_110 said:
If this is the case, then why are turbine engine blades, firearm barrels/chambers, revolver cylinders, railroad tracks, vital pieces of infrastructure, etc. produced from ingot steel?

While Charpy test results may look impressive on paper, how well do they really represent real-world scenarios? Until skyscrapers are erected with powder steel I beams and aircraft carriers hulls are constructed from powder steel, I am personally not convinced.
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Cost, availability ect have a lot to do with it. ;)

In those types of things the jobs go to the lowest bidders so cost of materials are a big factor.

The aerospace industry is a whole different world and there are some powered steels that are and have been used.

The steel treatments are at a much higher standard than in other industries, HT in 30 Bar+ Furnaces.
 
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Ankerson said:
The aerospace industry is a whole different world and there are some powdered steels that are and have been used.
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Are these parts highly stressed?
Are they critical parts that have to endure impact and flexion to keep the plane in the air? If so, which powder steels are employed? I'd be interested in knowing, as my two favorite ingot knife steels are 154 CM and BG-42; which are both utilized by the aerospace industry.
 
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