Recently, a friend asked me: Mr. Li, the metallographic sandpaper in our laboratory has been used very old. The surface feels smooth and the grinding particles have been basically ground flat. However, the imported metallographic sandpaper is too expensive and it's a pity to throw it away. Moreover, the surface of the sample we ground with this old sandpaper looks smoother and has better reflectivity than the surface ground with the new sandpaper. Therefore, Is old sandpaper better at grinding than new sandpaper? Isn't it too wasteful to throw away metallographic sandpaper when it's worn out?

I have also consulted with the technical engineers of the manufacturer of metallographic sandpaper regarding this issue, and the conclusion given to me is" It's not like this;, Undoubtedly, the grinding effect of new sandpaper is definitely better than that of old sandpaper! So why?

The editor summarized the reasons explained by the technical engineers of metallographic sandpaper manufacturers as follows:

Taking the commonly used silicon carbide sandpaper as an example, the production of metallographic sandpaper uses adhesives (usually resin type) to fix sharp abrasive particles of silicon carbide on the paper base. Due to the fact that the grinding of metallographic sandpaper is a micro grinding process, the damage and shaping rheology caused by worn abrasive to the sample are greater than those caused by sharp abrasive particles. Listening is believing, seeing is believing. Below is a cross-sectional comparison of the new and old sandpaper, which clearly shows that the abrasive on the new metallographic sandpaper is sharp and sharp; After using metallographic sandpaper for a period of time, the abrasive has been broken, the edges and corners have been removed, and the abrasive particles are completely in the bonding layer. At this point, the material removal rate is quite slow, and the chances of rubbing and touching the paper substrate increase.

The grinding marks in the following photos were obtained by grinding with new and old metallographic sandpaper. Can you tell which one is better for preparing surfaces? Which one is ground with new sandpaper?

Do you need a hint? The grinding marks of the new sandpaper will be clearer, with one grinding mark stacked on top of another, presenting an image with a three-dimensional morphology. The grinding marks of old sandpaper no longer have a clear three-dimensional morphology, appearing to be on a flat surface; However, in this case, the depth of the deformation layer of the sample will increase exponentially, only because the wear marks are more planar, resulting in better reflectivity of the sample, creating a more successful fabrication illusion for you& Ldquo; What a painful realization& Rdquo;

Is it still a waste to throw away metallographic sandpaper when it's worn out? I know, based on the analysis provided by the editor above, I believe you already know the correct answer. Therefore, during the grinding process, do not be afraid of scratches. The clear, three-dimensional, and regular scratches brought by the new metallographic sandpaper represent the successful removal of the material. Timely replacement of metallographic sandpaper will help you obtain more ideal metallographic analysis samples.