MSR, mechanically self sustaining reaction.
When laser is used small explosions are observed, we think that they are a by effect of the temperature.
Try using diamond discs.
Kind regards,
Fernando Oliveira
You can use the EDM in my case it worked great for cutting composite zones samples of 85% vol. TiC.
Best Regards
Ewa
TiB2 and SiC are conductor so you could used of course electron discharge machining. That one reason we sinter this compound.
In my case, water cut has not worked.
The stream of water was diverted to carbides and cutting was very inaccurate.
The possibility to laser cut will depends on the laser type used and conditions applied. So you have to use appropriate laser and optimize conditions first.
1.Abrasive (CBN or Diamonds grains) water jet cutting is a solution.You may combine this with a ultrasonic vibration of the workpiece . 2. High speed cutting with a diamond wheel -in presence of a high efficiency cooling.
The composition of the material is 80%TiB2 and 20%SiC, we tried to cut it using EDM, but, it was not possible.The diamond tool option has been used, and it doesn't work, either. Finally, water jet cutting option has not been proved because we don't have the equipment to do it. Thx everybody for your ideas and comments! :D
That means that the mechanical properties are very high ... Not so bad as you think ....
I don't think the mechanical properties of these materials are bad, instead we suppose they're amazing, but we need to cut them to analyze the microstructure and to carry out a full mechanical properties evaluation.
There are a number of commercial abrasive WJC outfits - some are willing to do oneoffs/work with researchers to optimise odd materials as it can give them a commercial edge elsewhere or lead to longer contracts.
I also agree that water jet is a good solution. This technique is particularly useful to cut very stiff polymers reinforced with carbon fibers.
For such hard ceramic you should use LOW CONNCETRATION diamond wheel.
Water or oil coolant might work. Try to clean the wheel every 30 minutes or so. Good luck. It takes time.
We tried to cut it with a low concentration diamond wheel...and the rate was lower than 1mm per 24 hours (3 work days).
The sample is a cylinder, with a thickness of 12 mm and a diameter of 50 mm, so the previous heat treat, due to the extension of the cutting time, we think, would be useless.
We don't have the option of water jet cutting, and we don't know anybody with this technology close to us. If anybody has got this technique or knows somebody with it, please let me know, I am open to collaborate. Thank you so much for your help and comments! :)
JM
I cut my samples (80% ZrB2 + 20% SiC, similar mechanical properties) using the diamond wheel without problems. I think you only need to optimize the condition, such as the angle of the cutting, and sharpe the wheel during the cutting. EDM is a good option, but more complicate (specially if you don´t have direct access to it).
Can you tell me more details about: What kind of laser did you use (wavelength, pulsed or cw,...)? What is the shape that you would like to cut? The material thicknes to be cut is 12 mm, correct?
We am dealing with different kinds of laser cutting processes and maybe there are alternative solutions to be tested. When using a classical cw fusion laser cutting process this is causing significant heat impact. This may be the reason of the explosions. Temperature and heat impact can be reduced by short pulsed laser processes.
To carry out the laser tests, we used a CO2 laser source ROFIN model DC 035 3.5 kW peak power and beam quality factor K> 0.9. The optical path that guides the laser beam to the head is formed by copper crystals. It has employed a cutting head Precitec LD 30 C D50 Focal 5 ". The movement in X, Y, Z and rotating relative to the head piece, is achieved with a CNC table installed in the cell itself.
When laser processing or cutting ceramics heat impact needs to be minimized to prevent it from heat cracking and other damage. I made a study this year on ablation of different ceramics with one of our ultrafast laser sources ablating the material. I achieved ablation rates up to 27 mm³ per minute, depending on the material and parameters. 12 mm material thickness is in general very high for cutting with a laser ablation process and not very common (but not impossible). There are also some limitations. E.g. the angle of the cut edges is usually not exactly perpendicular meaning that the kerf has a slight "V"-shape in its cross section. I.e. the cut is wider at the top than at the bottom (which is notable at 12 mm material thickness). If EDM should not work fine, laser ablation could be worth thinking of.
Since EDM works with electrically conductive materials (workpiece and cutting tool), you might need to check the state of their conductivities. This would guild you to be able to select the appropirate EDM cutting tool that can cut it. Alternatively, if you discover that the composite's electrical conductivity is a bit low, you can try to create artifical conductivity on its surface by sticking a thin layer of copper powder on it. Once the machining process is initiated, the cutting would be sustained. You may wish to try.
Ahaha.. Though case.
If you need them for mechanical test you will need to grind them to remove surface damaged zone. Laser might introduce thermal shock damage. Barsoum proposed EDM which does not involve high temperature local heating. Have you considered his suggestion?
What is the material's hardness?
Dear J. Córdoba. I think you should not give up the posiblity to use wire EDM, maybe trying diferent parameters. We have recently used it to cut ZrB2/SiC samples and it worked very well. The electrical conductivity of TiB2 is higher than for ZrB2 so it should work, unless you have a very high percentage of SiC in your composition. Regarding water jet cutting we succesfully cut both ZrB2/SiC and SiC, but to achieve a high tolerance for the bars you need is very challenge. Good luck!
Dear Dr. Cordoba, I asked for the matrix hardness, I guess you missed my question.
There is another possibility to cut parallelepiped samples and it is by Ultrasonic cutter or Ultrasonic drill. In this method the sample is immersed in liquid that contains particle which are harder than the matrix to be cut. To this liquid a "drill" is inserted. This "drill" is just a hollow pattern (circular, rectangular etc.) made of say steel. This drill is connected to ultrasonic transducer that vibrates the liquid and the harder particles hit the surface and thus cut the material. This method is mainly used for TEM sample preparation, e.g. in:
http://www.fischione.com/products/conventional-specimen-preparation/model-170-ultrasonic-disk-cutter
But it can be used for other purposes. The process is tedious, takes time but works.
The important issue is to find a powder which is harder than the matrix. B4C and commercial diamond are two such powders.
Good luck
Dear Dr. Yeheskel,
Sorry for the delay in my answer, I have been on holidays for a while. The hardness of the material is aprox. 23 GPa.
José
Dear Dr. Cordoba,
A colleague of mine (Prof. N. Frage from Ben Gurion University-Israel) works with similar material. Here is his reply:
"We use disk diamond and modern cutting machine ( the later very important) which allow to vary speed and applied load. They have to try, try and again try." I guess what he means is that you will have to optimize wheel speed and load.
Good Luck.
Ori
BTW my previous reply regarding ultrasonic drill (UD) stil holds. If you succeed in cutting a plate/disc from your boul, you can then use UD and cut few samples from the same disc.
Dear Dr. Cordoba,
I machined composites with close 25 vol% diamond particles using high speed cutting saw (but the material hardness is ~ 15 GPa). As other researcher mentioned, angle is one of the important parameter. Also, keep high rotation speed but less feeding rate (or rate of cutting) while using 250 micron thick diamond disks.
Pathi
Dr, Cordoba,
In my work group we use the diamond disk and a cutting machine (well adjusted and lined up to minimize vibration). The same as presented by Dr. Yeheskel. We use to cut small samples of materials with hardness of ~20GPa.
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