For natural stone or concrete machining it is common to use monocrystalline synthetic diamonds with a grain size of 300–400 µm. Grinding segments which contain these small diamonds are directly brazed on circular saws or drill bits. The most common fabrication routes for grinding segments are vacuum sintering and hot-pressing.
The distribution and the crystallographic orientation of the diamond grains in the finally sintered grinding segments are purely statistical. This makes an exact determination of the correlation between diamond orientation and wear behavior particularly difficult.
Thus, a group of scientists from the Technical University of Dortmund, Germany, have introduced a new method to explore the crystalline orientation of the cubic diamond lattice by means of SEM-assisted electron backscatter diffraction. Generally, EBSD-mappings are performed on different metal alloys used for quality assurance and to get information about the microstructure regarding grain orientation, grain size and distribution. To determine the orientation of monocrystalline diamond grains, however, with an EBSD system is not conventional.
In a recently published paper, Wolfgang Tillmann and coworkers focus on this new field of application for the EBSD-technique. Both, the detailed preparation and the testing procedure were shown.
The investigations of the TU Dortmund researchers show the potential of this method. The first statistical evaluation was performed and revealed that grain orientation influences forces and tool wear. However, more detailed investigations of these influences are necessary and part of their actual work. Further investigations will show how the transformed grain orientation may be used improve prediction about forces and tool wear.
Image: MR LIGHTMAN / FreeDigitalPhotos.net
