Metallurgy of Steel for Bladesmiths- Dr. Verhoeven

[EOU]

That does sound interesting Me2. Could you begin with an overview of phase diagrams for those of us unfamiliar with the subject?

[me2]

Sure, it's been a while since I've discussed them, so that's a good place for me to start as well.

First, the usual ones to start with are binary equilibrium phase diagrams. That means there are only 2 elements, and heating and cooling rates are very slow, ie at equilibrium. Adding even trace amounts of other elements can change the diagram. Heating or cooling rapidly will change them too. This leads to their main drawback. Few things are processed at equilibrium, and few systems are as simple as just two elements.

[me2]

So that's part of what it won't do. What it will do is allow one to estimate the temperature needed to get the phases desired, the relative amounts of those phases, and the approximate composition of the phases. Even though the binary equilibrium phase diagrams are simpler than what is used, they are still very useful as a starting point, and as a starting point for understanding ternary phase diagrams. I don't anymore, so won't go into those.

So, with the binary diagram for iron and carbon, one can choose a temperature for a steel like 1095 to get the phases desired for the hardening temperature. For a steel like 1065, a temperature can be chosen to remove undesired phases.

[EOU]

Thank you Me2! Part two of your post puts the subject into perspective for us. It is, however a horse of a different phase or a phase of a different color from the phase studies (non-metaluurgical) that we are familiar with. Thanks again.

[me2]

What kind are those?  

On a side note, I was exploring bronze for use in knives, and those diagrams are a fair bit more complicated than steel.  Various brasses and bronzes will form martensite too, just not as strong as steels.  Fyi, martensite does not appear on binary phase diagrams, as it is not an equilibrium phase.

[Mike Brubacher]

"What kind are those?" 

I'll answer your question for EOU here Me2. In a previous life I started a company that developed a new approach to an old idea called differential phase for the purpose of distance measurement. Three members of that old team are still here at EOU in one capacity or another. We adapted the principle to work in conjunction with laser diodes that were modulated at high frequency (100mghz). In fact, a single laser diode might be modulated at up to 4 different frequencies i.e 99, 99.2,99.4,99.6 during a single measurement event. The phases of both transmitted (via beam splitter) and received light, at each frequency, were compared to each other and then a reference frequency that was fixed at a very precise 455 Khz. The further the light had to travel (round trip) the greater the shift in phase. Sold the technology about a dozen years ago.

[me2]

Oh. I thought maybe it was related to power transmission.

I'll post more regarding diagrams when I get back to my laptop

[scott.livesey]

a related text of Dr. Verhoeven is Experiments in Knife Sharpening. here is a link you can download https://archive.org/details/Experiments_..._Verhoeven
Mike, you development sounds similar to the old time domain reflectometers we used in the navy to find cable or wave guide breaks.

[Jan]

Mr. Scott, Mr. Mike, I feel among you as in the Nikola Tesla family.

Jan

[Mike Brubacher]

Yes sir Scott. Spent a fair amount of time at Norfolk myself working with the Navy. Ships and planes run on fiber these days and have done so for some time now. Not up to date on how its done today but OTDRs used to either map and calculate attenuation in a fiber and/or actually tell you where a fault (break) was located. Fault location was done, in my day, using TOF (time of flight) techniques as opposed to phase. TOF is pretty straight forward when not much resolution is required. Generate a nanosecond pulse, start the clock, log the pulse reflection back in and stop the clock. If you know the speed of light and the index of refraction of the fiber you can locate the fault +/- a meter or so. Light travels about a foot per nanosecond in air so if you want to get high res with TOF then somebody has to invent a cheap picosecond clock (maybe they have for all I know) or do an interminable amount of averaging. Differential phase gave us about 1mm at 100mhz. I'd be surprised if they don't  do better than that today.