Occasionally, some users ask me, 'The surface of a sample ground with worn out old metallographic sandpaper looks smoother and more reflective than the surface ground with new metallographic sandpaper. Therefore, is it possible that old metallographic sandpaper has a better grinding effect than new metallographic sandpaper?'?


Conclusion: That's not the case. Undoubtedly, the grinding effect of new sandpaper is definitely better than that of old sandpaper! Based on what I have learned, Chain Energy Metallography Editor will analyze for you:


Let's take the more common silicon carbide metallographic sandpaper as an example. The production process of sandpaper is to use adhesives (usually resins) to fix sharp abrasive particles on the paper base. Due to the fact that the grinding of metallographic sandpaper is a micro grinding process, the damage or shaping rheology caused by worn old abrasive particles to the sample is greater than that of sharp new abrasive particles.

    As shown in the above figure, when looking at the cross-section of the new and old metallographic sandpaper under the microscope, a clear contrast can be seen between the two. The abrasive on the new metallographic sandpaper is sharp and protruding, and after a period of use, the abrasive will break, the edges and corners will be cut off, and the abrasive particles will also be completely in the bonding layer. At this time, the removal rate of abrasive particles on the material is relatively slow, and the chances of rubbing contact increase.

    The grinding marks shown in the above figure are obtained by grinding with new and old sandpaper, respectively. What do you think is a better way to prepare surfaces?


Here's a hint for you: The grinding marks on the new sandpaper will be clearer, with a three-dimensional image, where one grinding mark is stacked on top of another. The grinding marks of old sandpaper no longer have a clear three-dimensional morphology, appearing to be on a flat surface; But in this case, the depth of the sample deformation layer will increase exponentially. It is only because the grinding marks are more planar and the sample has better reflectivity that it gives people a more successful illusion.


With so much talk, I believe you, the smart one, already know the correct answer. So, during the grinding process of metallographic samples, do not be afraid of scratches. The clear, three-dimensional, and regular scratches brought by new sandpaper represent the successful removal of the material. Timely replacement of sandpaper will help you obtain samples with less residual damage.

    Therefore, in order to obtain an ideal metallographic grinding surface, it is necessary to use it when necessary, and replace it with old metallographic sandpaper! As long as you don't waste, make the most of everything.