In the preparation process of metallographic samples, whether it is metal, composite materials, electronic materials, etc., the use of metallographic sandpaper is basically the first step in sample preparation, with the aim of removing damage and deformation layers caused during the cutting process. It belongs to the rough grinding process and prepares for subsequent polishing. Therefore, this process is a crucial step. If not handled properly, it will affect the effectiveness of subsequent processes and even cause the sample to not be ground out, Unable to conduct subsequent metallographic analysis. In view of this, the Chain Metallography editor has a few suggestions to share with friends, and I believe they can be helpful for your sample preparation work.
Suggestion 1: Replace metallographic sandpaper in a timely manner

From the above figure, it can be clearly seen that the new metallographic sandpaper grinding particles are sharp and sharp; The edges and corners of the abrasive particles are ground and broken using old metallographic sandpaper, and the abrasive particles are completely buried in the bonding layer. At this time, the metallographic sandpaper has poor grinding ability, low removal rate, and an increased chance of rubbing the paper base. The surface of the ground sample is shown in the comparison diagram below.

The left image in the above figure shows the wear marks of old metallographic sandpaper, while the right image shows the wear marks of new metallographic sandpaper. The obvious wear marks on the right are clearer, with one wear mark stacked on top of another, presenting an image with a three-dimensional morphology. However, the grinding marks on the old sandpaper in the left image do not have a clear three-dimensional morphology, and it appears to be in a smooth plane. Does the left image seem to have a better effect? Wrong! Because in this case, the depth of the deformation layer on the surface of the sample will increase exponentially, only because the wear marks are flattened, so the surface of the sample has better reflectivity, creating a more successful illusion for you. Therefore, remember to replace the metallographic sandpaper in a timely manner when it is worn out, and do not hesitate!
Recommendation 2: Thoroughly rinse the sample

After grinding each grade of metallographic sandpaper, the sample must be thoroughly rinsed, and this step must not be omitted to avoid cross contamination. Otherwise, the large grinding particles remaining in the previous process will cause more and deeper scratches on the surface of the sample, which are difficult to remove, and sometimes even lead to more severe grinding. I have personally experienced it before, but I can't help but make a new sample. Therefore, please remember to thoroughly rinse the samples and grinding discs before replacing different grades of metallographic sandpaper.
Recommendation 3: Avoid embedding grinding particles

When using metallographic sandpaper to prepare softer low melting point metals, it is common to embed small grinding particles. This can be done by applying paraffin or candle wax to the surface of the metallographic sandpaper before grinding, and then conducting normal grinding to effectively avoid embedding problems. Of course, you need to be careful not to apply the wax layer too thick. Otherwise, it will significantly reduce the removal rate of metallographic sandpaper. Just lightly apply a little, and you can master it by trying a few times.
Of course, to avoid embedding, polishing paste can also be used instead of metallographic sandpaper, or diamond grinding discs can also be used. Whether these methods are used mainly depends on the material of the prepared sample and the experimental purpose, which you can flexibly grasp.
The above are some suggestions shared by the metallographic editor of Lianneng. I believe that when using metallographic sandpaper for grinding and polishing, these sincere suggestions are enough for you to grind the sample to the desired shape!
If you encounter any problems that cannot be solved by the above suggestions, please contact the application engineer of Chain Metallography. Professional advice will definitely help you cope easily. There are solutions to any problem, and we will face and explore together with you.