Damascus vs. Super Steels - Testing a Dozen Different Damascus Steels!

I did a giant Damascus study with a bunch of different steel combinations in the Damascus and almost every single test surprised me for example every Damascus maker knows that the key to the best Edge retention Damascus is to have two high carbon Steels in the Damascus and instead what if I told you that when we use soft nickel with the high carbon steel that it cut longer than all of the double high carbon mixes I have studied many many of the available knife Steels carbon Steels High alloy steel stainless Steels high speed Steels you name it I have tested most of them what I have tested very little for knife steel nerds is Damascus steel which in some ways is surprising well my father is named Devin Thomas he's one of the greatest Damascus makers of all time we were asked by the blade show to present on some subject my father and I and we chose to do performance at Damascus it hasn't been studied that much really and so we did the biggest study ever performed on the performance of pattern welded Damascus and that's what I'm going to present to you Bill Moran famously reintroduced Damascus to the new Custom Knife industry in the early 1970s and at that time they were making all sorts of claims about the amazing performance of Damascus one of the things they talked about was the so-called Damascus cutting effect and they said that Damascus would outcut a plain steel because the soft layers would wear faster and the hard layers would stay sharp leading to a serration or a saw-like cutting effect and that that would lead to Damascus cutting logger so these were things that these guys were saying especially in the 1970s about Damascus they also said that toughness would be better they said it was similar to like plywood or a laminated bow that the laminated materials would be more resistant to fracture than a straight material and they also said all kinds of weird things you know like Damascus took hundreds of hours to make or so much coal that it didn't even make sense and so all kinds of stuff about how Damascus was this incredible material just like they talked about in the Legends so this is another thing that we wanted to test is were those old legends true or are they just myths that we are happy to move on from now one thing about the Damascus cutting effect is that they said it would happen by laminating low carbon and high carbon Steels together but carbon is a tiny element and it diffuses very rapidly especially at the temperatures required for forage welding steel together and they've done experiments and simulations on this such as from Dr verhoven and bladesmith Howard Clark and they determined that at normal layer counts and normal Forge welding temperature Carbon ends up fully equalized in the steel so you can start with low carbon steel and high carbon steel but you end up with medium carbon steel at the end because carbon just diffuses so rapidly and it wants to be even throughout the steel and so you end up with two hard Steels so sort of the fundamental basis of this Damascus cutting effect did not occur with these early knives however there are a couple of ways you can still make hard and soft layers in Damascus one is to use steel plus pure nickel because the carbon doesn't diffuse into the nickel and even if it did the nickel still wouldn't Harden like this deal does so you get hard steel and relatively soft nickel and you can get them Crossing at the edge depending on the layer the layering and the patterning another way to do it is to use two Steels with different Harden ability levels so Harden ability is how slow you can cool steel from high temperature and it's still Harden so a water hardening steel has low Harden ability you have to quench it in water or have a thin cross section and fast oil for it to harden a high hardened ability steel is air hardening so you heat it up hot and you can just leave it in air and it will harden so if you combine a water hardening steel and an air hardening steel and then cool it in air the air hardening steel hardens the water hardening steel does not and then you get hard and soft layers so it is possible to create the hard and soft layers which may lead to the Damascus cutting effect but we want to test does it actually happen if you do have hard and soft layers and would it be beneficial if you did have hard and soft layers would you get some kind of serration effect in a slicing cutting test so one of the test that we did was with 1095 and pure nickel so that we can look at this Damascus cutting effect we also looked at a whole range of different combinations you know popular ones like 1084 and 15 and 20 that's probably the most common uh combination especially in the last 20 years or so and 01 and L6 and then we looked at some so-called high performance combinations like crew Forge V with 15 and 20 or Apex Ultra and L6 to see if double high carbon combinations give us better Edge retention so we're going to look at those as well as the toughness of these different combinations first with the low Wildlife Steels because they're more common then we'll move into the high alloy and stainless stuff we look at so many things but let's let's just start here so another important aspect of Damascus is the patterning itself for example when you give the steel a ladder pattern the layers go in a wave along where the edge will be so when you have a thin Edge you get crisscrossing of the layers across that edge as opposed to a random pattern where they are straight layers when we did Catra slicing Edge retention testing we saw consistently that the latter pattern out cut the straight layer random pattern so for example here we have Apex Ultra which is a high carbon steel with Vanadium and tungsten additions for Edge retention along with L6 a 0.7 percent nickel steel for contrast it does get hard but its wear resistance is significantly lower than the Apex Ultra so I have that compared with 8670 which is a similar Steel to L6 so it gets lower Edge retention it's at a little bit lower hardness and it has less wear resistance than Apex Ultra so it tests lower but when we combine the two Steels Apex Ultra and L6 in a straight random pattern we get a test which is roughly in between Apex Ultra and 8670 or an L6 that makes sense we've got a 50 50 combination we get something roughly in the middle between the two Steels however when we did a ladder pattern when we got crisscrossing along the edge then it cut almost to the level of the straight Apex Ultra so this was a little bit of a surprise we thought the latter pattern might help but even introducing a lower wear resistant steel it cuts similarly to the higher wear resistance of the two Steels in this case the Apex Ultra now let's look at the other low alloy Steels that we tested so again you can see that 1.2419 and 15 and 20 cut very well 1.2419 is another high carbon tungsten alloy steel like Apex Ultra is uh crew Forge V is a Vanadium alloy steel and when it was used with 15 and 20 it did well uh o1 and L6 even though it was in a random pattern it did pretty good in this test in part due to its high hardness it actually did similarly to Apex Ultra and L6 in a random pattern uh oh I should also note that the crew Forge v15 N20 it performed about the same as straight crew Forge V so again the ladder patterning seems to have helped with its performance 1084 and 15 and 20 did okay you know again those are relatively low wear resistant Steels at 60 Rockwell in a random pattern so it did not do anything surprisingly awesome it did how we expect it to do and o1 L6 bainite it was lower in hardness and so it's at the bottom of this chart looking at the microstructures of some of those Steels you can see what gives the Steels higher Edge retention and higher wear resistance so for example a steel light crew Forge V it has a significant Vanadium addition and so there are hard Vanadium carbides in the microstructure you know here is a relatively large Vanadium carbide those hard carbides resist wear and therefore it cuts longer in a slicing Edge retention test and if we look at a low lower carbon combination like 1084 and 15 and 20. you know they are much lower in carbide there are not as many clearly evident carbides because they are close to the eutectoid composition meaning there's not extra carbide after you heat them up before quenching them and so that steel has lower Edge retention and there are Steels in the middle like o1 and L6 where there's some carbide in there in the 01 especially and 1.2419 there are fine iron and tungsten carbides throughout the structure and that gives it higher wear resistance and therefore higher slicing Edge retention however there is one low alloy combination that did better than all of the others and that was 1095 with nickel so yes we did it we proved that there is a Damascus cutting effect the one thing that I never thought I would say the Damascus cutting effect is a real thing in a slicing Edge retention test in this case the Catra the 1095 and nickel outperformed Apex Ultra and L6 it outperformed crew Forge V and 15n20 it outperformed all of the other steels now you can see that the composite hardness reading here is only about 51 that is misleading because the soft nickel reduces the measurement in the Rockwell hardness test however when I used a 60 Rockwell testing file it skated on the 1095 meaning the 1095 is harder I estimate it to be around 6162 Rockwell 1095. but we indeed showed at least in a ladder pattern that 1095 and nickel showed greatly improved Edge retention over straight 1095. so I looked at the worn Edge after the test and you can see black lines from the nickel wearing in the edge during the test so there's about eight percent nickel so there's not a huge amount of nickel but enough to make a difference and when you zoom in even further with high magnification you can see the worn layers of nickel and then at the very edge a little worn spot you know leading to potentially this serration effect so we confirmed the Damascus cutting effect I didn't think that was going to be found in this study but we found that looking at the microstructure it looks like normal 1095 along with nickel the nickel resists etching so you get nice bright layers from the nickel then these dark 1095 with small iron carbides throughout so some quick definitions about what Damascus we're looking at we're looking at pattern welded Damascus meaning two different materials two or more different materials laminated together and we frequently get the question by people what's better Damascus or the new super Steels this question doesn't really make sense because you can theoretically Forge weld any materials together so if you use two super Steels together then what are we even asking are two super Steels better than one super steel I guess just the question doesn't make sense the performance of the Damascus is going to be controlled by a variety of factors such as which materials did you forge weld together are they Forge welded properly or are there welding flaws or impurities between the layers what is the layer count how thick are the layers and what orientation are the layers when we pattern it it changes the shape and orientation of the layers which can impact our performance depending on the direction that we are testing so all these different things can affect Damascus and again this question of super Steels versus Damascus that question makes no sense and in this study we will test a couple of super steel combinations of Damascus another thing I did recently was publish a brand new book The Story of knife steel innovators behind modern Damascus and super Steels and this book was an exploration of the history of knife steel itself the metallurgists the knife makers the knife companies that introduce different Steels that looked at different Heat Treating techniques that pushed the boundaries in different areas and the book is not just a series of dates or just pictures though there are many many pictures color pictures in the book but I tried to get as many first-hand accounts as I could from knife makers and metallurgists so you hear the story from their own lips you hear why they did things how they got to different conclusions and it was just a really fun book to work on I spent probably a thousand hours on the book about 18 months of active work on it and one of the fun things is reading what were people saying about knives and steel at different times okay let's transition to toughness one really important aspect of toughness is the direction that you test in the main reason for this is because steel is hot rolled at the steel mill and therefore it has elongated features along the rolling Direction two big ones are manganese sulfides which are impurities in the steel so the steel companies try to minimize the sulfur content in the steel and they get it as low as they can and then to help with the rest of the sulfur they add manganese as iron sulfides are really bad but manganese sulfides are ductal at High rolling temperatures and therefore they elongate and they make the steel somewhat less tough when you have a crack growing along that direction another issue with tool Steels is that we have lots of carbide in this deal and carbides will also elongate along the rolling Direction so both of these factors carbide structure other microstructure features and impurities are all elongated along the rolling Direction and therefore when cracks grow in that direction toughness is lower so here is a schematic showing our rolling Direction and this is what's called a transverse toughness specimen and it breaks along the rolling Direction and so the cracks can form along those sulfides or carbide stringers or other microstructure features and therefore toughness is reduced however if we do a longitudinal specimen the crack grows perpendicular to The Rolling Direction and therefore the toughness is higher than a transverse specimen now with Damascus this is largely unaffected at least in the type of laminate that we're discussing here another type of toughness we could discuss is bending where we might get fractures that grow through the different layers but when we talk about a knife edge we are getting an impact sort of to the side where it matters if we're in the rolling direction or transverse Direction so if we have a knife blade that's along the rolling Direction like this one on the right and then we are chopping for example it is similar to a longitudinal toughness test and this is the orientation that I recommend in my book knife engineering however some knife makers will put knife blades in the alternate orientation perpendicular to The Rolling Direction and then when we're chopping then the cracks will grow in along the rolling Direction which reduces our toughness several years ago my father and I did a study on the toughness of crew Forge V and we measured in both orientations longitudinal and transverse and as expected the transverse toughness was significantly lower than the longitudinal toughness and this was consistent across hardness though the two values get closer together at higher hardness there's a bigger spread in the 61 and a half Rockwell specimens than in the 66 and a half Rockwell specimens however when we tested the crew Forge v15 and 20 Damascus in both orientations we found that the longitudinal and transverse toughness was very similar and this is a pattern that we saw with the rest of our materials and what I think is happening is that we have an effect of the patterning so this deal was made by Salem Straub with a W's ladder pattern and the latter pattern creates these lines that go across the rolling Direction so that cracks can grow through them however I did not expect this factor to be important because if you look at the cross section it's not like there are straight lines that go through everywhere there are more wavy lines but apparently this is enough to reduce our toughness and consistently we saw with ladder patterned steel that the longitudinal and transverse toughness was very similar so the latter patterning led to better Edge retention but worse longitudinal toughness another test we did was with the Apex Ultra L6 Damascus where we tested both ladder pattern and random straight layer Damascus in both orientations in this test we saw that the random pattern steel had better toughness than the ladder pattern uh in both orientations so the the random pattern was better ladder patterning led to a reduction in toughness especially in longitudinal toughness however we were very surprised at these toughness results because the Apex Ultra Damascus was significantly lower in toughness than Apex Ultra itself and especially so when compared with L6 Damascus so what is going on well we we looked at the microstructure and we found that the Damascus had a lot of grain boundary carbide now grain boundary carbide is an issue in high carbon low alloy Steels the higher in carbon you are the more that the carbide wants to form on grain boundaries and my father had forged at low temperature similar to the normalizing temperature and thought that this would eliminate the grain boundary carbide but that didn't happen so after we saw this low toughness and saw that the issue was grain boundary carbide we took the same steel and we normalized it at high temperature and plate quench to ensure no grain boundary carbide formed then we did a grain refinement from 1450 and annealed from 1450. and then retested this time we looked at two patterns one in ladder pattern and another in a pattern called snakeskin so this was to test if patterning itself is having some effect on the toughness or if we have a different type of pattern if toughness improves so unlike ladder pattern where there are lines that are perpendicular to The Rolling Direction snake skin is not it's in the opposite orientation and they're rounder features when we tested snakeskin the toughness was slightly better than Apex Ultra on its own so some benefit of the L6 and the latter pattern was reduced versus straight Apex Ultra so ladder patterning improves Edge retention but it is worse for longitudinal toughness now another thing to note is that the toughness even of the snake skin is very similar to Apex Ultra alone even though it has that tougher L6 in the mix and this is another thing that you will see with our other combinations tested that the toughness is mostly controlled by the less tough of the two Steels so this is like a fracture begins at the weakest link scenario so when you've got a tough steel and a less tough steel that tough steel isn't doing that much for the overall toughness at least in this type of toughness test and this fact was confirmed with an even more extreme case which was 1095 and nickel so nickel is a soft very ductal High toughness material in combination with the 1095 but this 1095 nickel combination tested similarly to 62 Rockwell 1095 on its own the nickel did not really benefit it for toughness we also had both 01 L6 in martensite and in bainite as expected the bay night did better because this was a random straight layer Damascus the o1 L6 was its toughness was relatively good again you can see on this chart the difference between ladder pattern and snakeskin on the Apex Ultra L6 we already discussed the crew Forge v15920 the 1.241 915 and 20 Damascus was also not very high in part because of its ladder patterning the best deal that we tested in the low alloy category was the 1084-15 and 20. so both of these are high toughness Steels so the 15 and 20 is tougher because of its nickel content but 1084 is no slouch either so it tested similarly to 1084. more similar to 1084 than the higher toughness 15 and 20. but also it was in random pattern which helped its toughness versus the latter patterned conditions another thing to note is that 1080 4 and 15 and 20 was the only broken specimen where there were visible welding flaws or at least delaminations and this did was not detrimental to the toughness somewhat surprisingly these welding flaws were also visible in the microstructure of this deal there were some of these black lines in between the 1084 and 15 and 20 layers so again they were visible in the fractured specimens and in the microstructure but they did not negatively affect the toughness in this test so I should also talk about the people who made the Damascus that we tested the 1084 15 and 20 came from Gambler custom made by Peyton pelland the 01 L6 was from Casey Lund with samples that were machined by Will Brigham another Damascus maker the crew Forge v15 and 20 was made by Salem Straub my father Devin Thomas made the Apex Ultra L6 and the 1095 pure nickel and the 1.2419 15 and 20. High alloy Steels that we're about to get to I got some damasteel which is made with rwl 34 and pmc27 I also got some s90v20cv from Seth Burton of Cosmo knives and then the rest of the high alloy stainless combinations came from Devin Thomas so those included 3v154cm 19c27 with 302 19c 27 was 716 aebl was 716 and abl with 154 cm now Damascus studies are very expensive because the steel is very labor intensive so I bought steel from most of these knife makers and I also paid my father to make a bunch of the specific steel combinations for study you know he can't just take two three four weeks from working to make a bunch of Steel for fun science studies he has to make a living as well so between all of that purchase deal and paying my dad this is one of the most expensive tests that I've ever done for knife steel nerds so you know Damascus is expensive material this study was around 10 grand and I bring this up to say that if you like this type of work you should support us on patreon so I use the patreon to fund these types of studies there's no way I could get away with spending 10 grand on a fun knife still study just because I want to that's just too much money and that's what patreon lets us do I've been doing patreon for a couple of years now originally I had no plans on getting any money for knife Stone nerds but when I started to think about what would be possible with some money I set up the patreon for that and I just spend that money like it's free so I've spent a surprising amount of money on the experiments that have been done for this website and the YouTube channel and it's been amazing we've done you know this is the biggest Damascus performance study ever performed and it's all because of patreon so if you're interested please go on patreon.com knife still nerds and that funds this type of research biggest of the studies that I did with my father for this set of experiments was on whether or not we can improve the microstructure of Steel through high layer count Damascus so we chose abl and 154cm in a 50 50 ratio abl has a really fine microstructure due to its design and processing by udahome so its microstructure is finer than most powder Metallurgy Steels just through sheer metallurgy but 154cm has relatively coarse carbides like other non-powder Metallurgy Steels there are powder Metallurgy versions available including cpm154 and rwl34 but for this study we wanted to see can we decrease the size of the carbides through forging so for example if you've got a steel with a really high layer count we can get the layers thinner than like one micron which is significantly smaller than these carbides in the normal conventionally available steel so can we Forge down this deal to the point where these carbides are submicron through a high layer count that is the question we wanted to answer so we did a series of different layer counts so we had 25 layers 125 layers 625 layers 3125 layers and we had that most of them were in ladder pattern but we had one condition where the 3000 layer was forged down further so it remained unpatterned So Random straight layers rather than the ladder pattern like the others so if we look at the microstructure in the 25 layer steel the microstructures of the two Steels look basically the same so we have regular 154cm with relatively large carbides and we have abl with its fine carbides at 125 layers the distinction between the two layers is not as sharp in 25 layers but they're still pretty consistent we've got 154cm with larger carbides and aabl with fine carbides you can also see where some of the carbides are starting to be across the boundary between the two Steels so it seems like those carbides once the steel is homogeneous the carbides are able to go outside of that transition once we get to 625 layers the layers are more difficult to see and the transitions are more diffuse so earlier in this video I talked about how carbon diffuses very rapidly and that it's not carbon that leads to differences between the two Steels the difference in etching Behavior comes from other alloying elements and when you combine aebl and 154cm the reason why they have contrast after etching is primarily because 154cm has four percent Molly while aabl has none however as we get to higher and higher layer counts those layers get thinner and thinner they spent more time at high temperature there's more diffusion and so we're getting more diffusion of molybdenum between the two Steels and so we get these more diffuse transitions between the two Steels and also the carbides are getting smaller but we're also seeing them cross the transition boundaries between the two steels at 3125 layers we can no longer see the layers so you can't see them really at all and we can tell for sure that the carbides are not smaller than our estimated two Micron layer thickness however the carbides are smaller than in the original 154cm steel and if we look at the unpattern 3000 layer count again the microstructure looks pretty similar so without a full statistical analysis we can't really tell how much smaller the carbides got however we can look at did our toughness improve by going down to thinner and thinner layers so we tested in both longitudinal and transverse directions and when they were ladder patterned the longitudinal transverse toughness was almost identical however the toughness did improve as we went to smaller layers thinner layers and a higher layer count when we tested the unpatterned steel which had approximately one micron thick layers if the layers are even still a thing there was a gap again between the longitudinal and transverse toughness to about the extent that we would expect again the toughness was closer to 154 CM than it was to abl but in this case we did see a benefit to having the two materials together especially in a high layer count so the lower layer count material was closest to 154 CM as we got up to a high layer count it was a little more in between the two steels however the problem with having a high layer count is that you know you can no longer see layers so what is the point of Damascus if there's no longer a pattern so we did get an improvement in properties but at the cost of a beautiful pattern one thing I noticed when analyzing the fractured specimens especially in the low layer count ladder patterned material is it did look like the crack was growing through individual layers so you can see that we had a crack growing through this layer and then the crack moved over to another layer and traveled up there and then it moved to another layer and then traveled up that one so this seems to confirm that the ladder patterning is leading to worse toughness because it has these preferential places where the crack can grow in an orientation consistent with the pattern so that seems to be what ladder patterning is doing we also measured Edge retention of the aebl154cm and we found no effect of layer count so in this case no effect on edge retention though a sizable effect on toughness uh so this makes some sense and it's still a little bit surprising and because it was in ladder pattern The Edge retention was much closer to 154 CM than it was to aebl however this was actually surprising because the very first Catra study that my father and I ever did was on aebl 154cm Damascus and in that case we found the Damascus to be right in between straight aebl and 154cm Steels and in that study we had three knives an aabl knife a 154 CM knife and then a 50 50 ladder pattern mix and so we found Catra Edge retention right in between the two and we're like okay that makes sense but we were using a Catra tester at Spyderco they were very generous in letting us use that we brought unsharpened knives and let Spyderco sharpen them because we thought that they would have a specialized method for it though they really did not at the time at that time they were just sharpening on a belt grinder and this may have been a case where just the sharpening of the abl154cm Damascus was not as good as the straight 154cm and made this satisfying uh split between the two Steels but in our new testing it really seems like in a ladder pattern that the edge retention is closer to the higher wear resistance Steel in this case 154 cm so I wanted to point out that some of our new results were the latter pattern leads to Edge retention closer to that higher wear resistance deal it contradicts our earlier study so we also tested a bunch of other high alloy Steels in different combinations so aebl is a standard razor steel we already discussed and 154cm it's an old standby bearing stainless steel 19c27 is a high carbon steel made by Sandvik now called Alima 716 is a 420 Steel on the upper end of carbon 302 is an austenitic stainless steel very low in carbon doesn't normally Harden rwl 34 is a powder Metallurgy version of 154cm and ATS 34 PMC 27 is a powder Metallurgy version of 12C 27 s90v and 20cv are very high carbon High Vanadium powder Metallurgy Steels and 3v is a popular powder Metallurgy High toughness non-stainless Steel so of course we also already talked about the aebl 154cm Damascus we also talked we're also going to talk about damasteal odama steel is a common stainless Damascus that's available made with two powder metal or G Steels rw34 and pmc27 I also tested some aabl 716 and 19c27 716 this is similar to the composition that Alima is starting to offer which is a 19c27 7c 27m02 steel so 7c27 mo2 is the same as 716. so my father had made some 19c 27 716 in the past and so we're able to compare with how a Lima steel is likely to perform though I wasn't able to get any in time we also looked at 19c 27 302 and abl 302 I have an old test that I will also compare with then two of the highest wear resistance Steels ever combined in Damascus s90v and 20cv from Seth Burton then we also have 3v 154cm so lots of high Ally Steels that we're going to be able to compare okay starting with the toughness the aebl 154cm we can see how its toughness changed relative to other Steels at different layer counts and the patterning so the 3000 layer random pattern Damascus it did almost as well as the damage deal somewhat surprisingly in part because the dam of Steel RDU wl-34 still has significantly finer carbides than the 154cm big carbides that we had at 3000 layers so that 3000 layer random did quite well the s90v 20cv also did very well so similar in toughness to those two Steels individually our best steel was aebl 716 so two high toughness stainless Steels combined together they had excellent toughness even in a ladder pattern so the random pattern we would expect to do even a little bit better however one minor surprise is that the abl 302 did relatively low this is the old test that I was talking about one that had a big surprise early on abl and 302 are both High toughness steel so why did we get such low toughness the 19c27 302 makes more sense because 19c27 has larger carbides in it so its toughness is not as high but the abl 302 these are both tough steel so what happened well when we looked at the microstructure we found that the 302 where normally it has no carbide was forming a significant amount of carbide and very large carbides earlier we talked about diffusion between two Steels because 302 has almost no carbon in it there is a lot of carbon diffusion that comes from the abl into the 302 and so carbides are going to form though it's surprising how big the carbides are it could be that we're getting some melting at the interface between the two Steels because when you go higher in carbon the melting temperature still goes down this is why cast iron has really high carbon so it melts at a lower temperature hence why it's called cast iron so they add a bunch of carbon to it the melting temperature is lower so when a lot of carbon is going into the 302 there is carbon that builds up at the interface between the two Steels and perhaps that is high enough where you get melting and then when it re-solidifies big carbides are forming though maybe there is some other mechanism in place all I know is that looking at this steel there are big carbides in the 302 those big carbides act as places where cracks can nucleate and then the toughness is low similar to other large carbide stainless Steels we saw something similar in the 19c 27 302 Damascus so there are already large carbides in the 19c27 but then there are also big carbites in the 302 from carbon diffusion from the 19c27 into the 302 so the 19c27 302 Damascus had similar toughness to the 19c 27 716 even though we might think that the 302 layers would help us for toughness but really they didn't the 3v154cm Damascus again its toughness is much closer to 154 CM than it is to the high toughness 3v so just like we've been discussing the less tough of the two Steels primarily controls the toughness behavior of the steel and adding a tougher steel to it does not help that much looking at Edge retention for these high alloy and stainless Steels as expected the s90v 20cv did excellent on the test this is despite the fact that it was not ladder patterned it had something that looks closer to snakeskin pattern which also helped its toughness but the edge retention was much higher than everything else due to those high carbon and lots of vanadium carbide in the steel so just like we would expect two high wear resistant Steels equals a high Edge retention Steel in a slicing Catra test the aebl154cm and damasteel did similar uh a minor surprise is this 19c 27 716 which did similarly to what we would expect 19 c27 might do on its own probably helped by the latter patterning and it actually did very similar to damasteel even though damasteel has the higher carbon rwl-34 in it the 3v154cm did about where we would expect it to go and the lowest was the aebl 716. so again these are the the lowest carbon combination that we tested so there's much less carbide in the abl716 and it did lower in Edge retention than the other higher carbon Steels as we would expect however it did very similarly to how aebl would do on its own presumably because the latter patterning boosted its Edge retention back up to the level of abl despite the lower carbon 716. another thing to note is that almost all of these Steels did better than any of the low alloy Steels because the chromium carbides in them are harder than iron carbide and that gives them better Edge retention in the Catra test so we'll also go through some of the micrographs of the high alloy Steels to discuss why they behave the way they did uh the 3v154cm Damascus you can see the large chromium carbides in the 154cm and the relatively smaller carbides in the 3v you can also see that there was significantly less 154 CM than 3v in this particular Damascus which even though it was mostly 3v the toughness still mostly reflected the coarser carbides and the 154cm and the reason for that is that the toughness is often greatly limited by crack initiation and so cracks initiate much easier in bigger carbides bigger carbides are just more brittle they fracture under less stress and so if a crack initiates then it's going to grow pretty rapidly you know these are very high hardness materials these knife Steels so crack growth is pretty rapid so the 154cm really reduced the toughness of the 3v154cm combination but if we look at aebl 716 these are both Steels designed for a very fine microstructure even though they're not powder Metallurgy and we see very fine carbides in both of the materials that are in the Damascus with 19c 27 and 716 we see fine carbides in the 716 though we didn't have the issue of large carbites forming like we did in the 302 combinations though fine carbides were still present in the 716 and the 19c27 had its typical microstructure with some bigger carbides present which reduces toughness with the s90v20cv Damascus it was almost sort of hard to tell where one material would begin and the other would end both are pretty high carbide Steels made with powder Metallurgy so they've got a lot of medium small carbides from that powder Metallurgy process both have a lot of chromium carbide and some Vanadium carbide in it but the overall microstructure is relatively fine when we look at the damask deal with rwl 34 and pmc27 there were some more diffuse transitions between the layers in this material which I believe is because they layer up powder itself rather than solid steel made from the powder so sometimes the layer transitions look a little bit different than the two solid materials that were used in other combinations we tested uh but the main thing to note is that the carbides are very fine throughout and that the carbides in the rwl-34 layers are in general finer than in our heavily forged 154cm Damascus here's another look at the broader microstructure so this is lower magnification you can see the Micron bar is a full millimeter and another thing to note is that the way this damage steel is made that the layers are straighter and more similar to straight random pattern at the edges of the bars so as you get to the edge it looks more and more like random pattern and as you get to the center then you get more of the wavy look so the damask deal was somewhat unique in that it had a combination of straight layers at the edges and then the wavy layers at the center so it would be fun if we could do some more tests specifically on this to see you know how does it affect things if we're in those straight layer regions or in the wavy layer regions but that will have to wait for another time if I'm ready to spend several hundred dollars on more damage deal so to summarize we found some big things in this study this is the largest study ever done on the performance of pattern welded Damascus and we've got some big conclusions the one is that we confirmed that the Damascus cutting effect is real which again is something I never thought I would say when we had hard 1095 and soft nickel and we tested it in an edge retention test we got a serration effect and higher slicing Edge retention ladder patterning led to better slicing Edge retention but worse longitudinal toughness due to the orientation of the layers when we tested toughness it was largely controlled by the less tough of the two Steels and adding a more tough steel really didn't help so the weakest link is what would lead to fracture initiation and then those cracks would grow through the steel there so there's no free lunch even when it comes to Damascus patterning you know you can manipulate performance through patterning but when you improve one thing you'll reduce another using low carbon 302 led to reduced toughness so there wasn't really a benefit from those soft layers for toughness in fact it was detrimental though abl and 302 are both two tough Steels and when we combine the two of them we got a not tough steel so sometimes there are steel combinations which are not really good for toughness at least uh we saw some delamination or welding flaws in the 1084-15 and 20 but that did not affect the performance of the steel which is a little bit surprising we also did that big high layer Damascus count study with aebl and 154cm so we did reduce the carbide size of the 154cm and the toughness did get better but the carbides were not smaller than the layer thickness because eventually once you have a homogeneous material that's Forge welded those carbides can go outside of the layer transition and a one micron layer thickness does not mean sub 1 micron carbides but by changing the layer count we did not see any change in Edge retention so there was a performance benefit we got higher toughness by greater reduction higher layer count and no change in Edge retention so there was an improvement but you also lose all of your pattern by doing that a higher wear resistance deals in Damascus like using Apex Ultra in low Ally Damascus or s90v and 20cv and stainless Damascus led to Greater slicing Edge retention this is totally expected when you use higher wear resistance Steels the knife Cuts longer so that is all anticipated I suppose though with how many surprises we found who knows but so that made perfect sense in our testing so one more time I would like to bring up my book again the story of knife steel I spent so much time on that book more time than anything I've ever worked on for my website or this YouTube channel and I really want people to read it I'm very proud of it some amazing stories in there from great knife makers and metallurgists so read their words I think you will be surprised by how they came to the conclusions that they did how they tested certain things why they had this idea or that one there's so much to learn in here uh you know you can really learn the history of how the knife industry itself formed you know how did we get to hear how to custom knives develop how did the production knife companies get better how did things evolve in China that's all in the book so even if you just want to learn about the knife industry in general and don't care about steel I think this book is great I also want to mention the patreon again patreon.com knife still nerds again this is the biggest study ever done in Damascus one of the most expensive I've ever done I would not be able to do these types of tests without support from patreon so thank you my patreon supporters so we do some fun stuff on there extra discussion some exclusive content I report early tests of things like for example I tested early I showed early tests of Magna cut on my patreon before anybody else saw those tests so that's an example of exclusive things you get as a patreon supporter so please come join us on patreon and hopefully we do more fun tests so everybody thanks for watching I hope you learned something

Channel: Knife Steel Nerds

Views: 45,945

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Id: T-fuk0ypQHI

Length: 50min 32sec (3032 seconds)

Published: Thu Jul 13 2023