Interessant! Der stirnseitige Abbrandkrater ist überraschend, das hätt ich nicht erwartet. Das Schliffbild der neuen Elektrode ist echt komisch, auch hier, hätte nicht gedacht das Wolfram zum schmieren neigt, normal ist das Zeug so hart/spröde, da hätt ich eher feine Ausbrüche erwartet.
Grüss Dich, Stefan! Danke für deinen netten Kommentar, verfolge deine Videos immer mit großem Interesse! Hoffe wir sehen uns irgendwann mal wider. PS: Das mikroskopische Schmieren hat vmtl. mit der lokalen Erhitzung zu tun.
Every solid at room temperature is just a frozen liquid, so when you add enough heat and/or pressure, it will flow like a liquid. So even Tungsten flows like a viscous liquid, at the cut edge of the chip. If the chips are small enough then the pressure is high enough and the surface looks like someone has dragged a scoop through the ice cream. Also, the sharp geometry of the tip hugely magnifies the current density and electric field, you can likely change this end crater size by flatter geometry at the tip but also by changing amps and ramps.
electron microscopy for the win on machining youtube! So as material science! So as Dr. Wang! Glory Glory for everyone! *Sorry about going a little bit crazy here, but it is a long time since I have seen such deeply satisfactory content - science and practice hand in hand, science in our everyday life - on display. I wonder if it would be interesting to see robrenz flat stone under the microscope, hm
I would love to know what's below the surface. I re-grind my electrodes by skinning the tip, as if sanding the contamination off and then a little into the W. Always works, so i've always assumed that contamination is only skin deep.
Really nice work! My only wish is that you examined some cross sections to evaluate the depth of penetration. By the way, La2O3 has a lower boiling point than W (4200C vs. 5500C). So it stands to reason that part of the cause of the La depleted regions is not just differing diffusion rates but the La2O3 boiling off!
Alex, just found your channel through your milling machine rebuild. Absolutely super content and especially the heat distortion series. I enjoyed it very much and finally managed to understand reasons behind it. The quality of your videos will surely make you much more popular here on RU-vid... if only more people would watch it from educational rather than entertainment purposes. Viele Grüsse aus Finnland! Jonas
Thank you very much for your kind comment, Jonas. I'm glad if you find the content useful. I fully agree with you, people seem to use the internet (and also youtube) mostly for entertainment. Kind greetings, Alex
Great content on your channel Alex! I heard you mentioned in one of Stefan's videos. Excellent series on the weld distortion stuff BTW. For this video it was also very informative. One thing to note with Tungsten is any little flake of W that contaminates the weld is generally bad. This is especially true on RT welds (radiographed) because the W with really stick out in a radiograph since W is so dense, most welds that are RT'd will fail the inspector. One really good practice is to run the electrode in at or slightly above normal weld current for maybe 10 or 15 seconds on a scrap piece. That way any little W flake will likely fall of in the scrap weld bead and not contaminate the good weld. P.S. I like to polish my electrodes and slightly ball the tip smooth.
Isn't the crater more likely due to sputtering, similar to DCEP cleaning cycle when welding aluminium? Argon and other gas gets ionized and hits the negative electrode, where it causes sputtering or oxidation.
Very interesting topic and great presentation of the material... I guess it doesn't hurt to have access to an SEM just laying around the shop. Keep up the great work, it's really appreciated. Also, think it would be nice if you ever get the chance to do an in-depth review of the SEM and its processes.
EDX can probe a couple of microns into the surface, which might help answer your question at 5:38. You'd need synchrotron XPS, sputtering, or a FIB cross-section to really be able to do depth profiling. We have a FIB/SEM + EDX at work, if you send an electrode I might be able to provide a FIB cut with EDX.
i wonder what the abrsive properties will be of the fat part were the aluminium with the tungsten crystals.....whould that behave like a lap? always intresting, the microscopic world.....there in the crater of minerals looks almost organic, like a coral reef with al sorts of creatures......
Great video,that cavity looks scary, Also watch you video on restoration of the Micron incredibly. I don't know where you learned all that so young,but I just know thet I'll follow you from now on. Keep going....
A good question. I assume the cavity will be larger, the higher the current. If I find the time I'll take some pictures of electrodes that had different amperages.
Nice video. From the scales I saw in the pictures, is there any reason why this could not be viewed with an ordinary metallurgical microscope? Beyond the xray specturm analysis of course.
Actually, a standard metallurgical microscope should be fine for this, too. However the electron beam microscope has much more depth of field and contrast, which may be a benefit.
I was always told you're not supposed to radial grind tungsten but instead grind it so the striations are vertical or axially aligned with the electrode, supposedly makes a more stable arc.
