Now for some details, but first I would like to stress that my intentions were not to stump anybody, nor intimidate. Some of us have seen images like this in books but they may not have caught our interest, I thought these were different because they were captured by a knifemaker, in a steel commonly used by many of us, from a bar that a few knives have already been made using some of the techniques that developed the effects presented. I thought it could kind of bring it to a more personal level for us. Some of the things are indeed present in our blades.
O.K, here we go:
#1 is a sample of 1095 steel that was heated to approximately 1800F (hoping to grow the grain for better viewing) and then cooled to 1100F. and held for 15 minutes before quenching. This first image is not close enough to make out the pearlite, but it is there. What I was really surprised by was the amount of pro-eutectoid cementite (iron carbide in excess of .83% carbon) that precipitated in the grain boundaries. This is why there is a wide white outline to the prior austenite grains. This is a bad thing! Cementite is very brittle stuff and fracturing tends to occur following the grain boundaries, so you know what that means for toughness. You can see why it would be very important to completely re-austenitize this steel and dissolve this stuff before hardening.
#2 is the same sample at high enough magnification for us to see the lamellar nature of the pearlite. What is particularly cool is where it is oriented. You will notice the most prominent zones of it in a delta configuration starting at a corner. This is a nice illustration of the way pearlite likes to nucleate from the intersections of grain boundaries. As a stringer of high concentrated carbide forms it depletes the austenite to either side until it forms bands of ferrite, which prompts another thread of high carbon and so on until we get this layered lamellar effect. Cool, isnt it?
#3 is the edge of the same piece. To be honest the dark patch is more of a red herring, since I believe it is a dried bit of oil that got stuck the steel, sorry. What I really wanted to illustrate here was how the grain boundary pro-eutectoid cementite just sort of vanishes before it reaches the outer surface. Why is this?... The hint that it was not heated in something like my salts give it away, and mete spotted it right away. Decarb!
We dont have any pro-eutectoid cementite near the surface because there is not enough carbon left there to make it.
#4 is actually what mete spotted, I am sure in his job this stuff was his sworn enemy when working with high carbon steel. I was happy to get such interesting and pronounced patches of pro-eutectoid ferrite, from the decarburization. This is actually steel so depleted of carbon that it cant form carbide, it cant even form pearlite, since that requires the eutectoid (.83% carbon) all it has left is mostly iron (ferrite).
#5 Now here we have something we are all more familiar with wanting. This is a piece of 1095 quenched in water. For photography reasons I etched it much darker, since martensite is quite white under the microscope. Arcing across the top of the frame is a micro-crack from the water quench, please note that this crack was not visible to the naked eye before the sample was prepped. This makes it very clear why a quench must be fast enough yet not too fast, not all quench damage makes itself known. Also note how the crack followed the grain boundaries so well. Without the crack you could not make out those boundaries, since all that carbide has been used up to make the martensite. If one is very good (and lucky ) they may be able to make out the previous boundaries due to the orientation of the martensite needles, since they tend to nucleate out from the grain boundaries when they form.
#6 is the same hardened sample at the edge to once again show the effects of decarb. Notice how the nice little needles just sort of peter out and you get those big islands of ferritic material. If this was at you knife's edge how well would it keep cutting? You would need to get rid of that skin of ferrite before you could start getting top performance out of it.
O.K mete, feel free to dive in now; I would like to get your input on what else there may be there.
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" . To be honest, what you see here is the result of what some could call an obsession that was spawned by all the myths and missinformation in the knifemaking field. I tended to retain all that boring science stuff from school and an awful lot of what I was hearing and reading about bladesmithing just didn't jive with what I knew. When something catches my interest I will pursue it relentlessly to the exclusion of other things, until it, or I, am exhausted (a trait that drove my teachers crazy 
