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Common knowledge about metallographic samples—clarified for you by the manufacturer of metallographic grinding and polishing machines.
Release Date:
2022-04-19
Metallographic polishing and mounting machine manufacturers believe that the purpose of mounting metallographic specimens is to adapt samples with unsuitable shapes or dimensions to the subsequent grinding and polishing steps, thereby obtaining the desired examination surface. For certain special materials, mounting is also intended to protect the edges or to prevent surface defects that may arise during sample preparation. In all cases, mounting must not compromise the metallographic microstructure of the specimen. During the mounting process, applied pressure and heat are the primary sources of microstructural damage.
Metallographic mounting machine manufacturers recognize that there are many types of metallographic mounting machines, ranging from simple laboratory heaters and molding die assemblies to fully automatic metallographic mounting machines. The automated metallographic mounting machine is a highly advanced hot-press mounting device that allows for convenient control over the shape and size of mounted specimens. Because the mounted specimens are easy to handle, they can be readily hand-polished and finished.
Metallographic grinding and polishing machine manufacturers believe that the key to the metallographic analysis process lies in the quality of sample preparation. A high-quality, flawless sample can accurately reflect the material’s microstructure, providing a reliable basis for the analytical data generated by metallographers. In addition to selecting the right equipment, the choice of consumables is equally important. Proper selection of consumables not only enables the production of perfect samples but also significantly enhances the efficiency of sample preparation. Let us now examine, one by one, the consumables we commonly use:
Mounting: Metallographic polishing and grinding machine manufacturers point out that when the material for metallographic examination is too small in size or has an irregular shape—such as wires, strips, foils, or tubes—it is difficult to hold securely. Therefore, mounting is employed to produce specimens of appropriate size and regular shape. Hot mounting utilizes a mounting press together with thermosetting materials such as bakelite (phenolic molding compound) and resins; these materials are opaque and available in a variety of colors, with black being the most common color for metallographic specimen mounting.
According to manufacturers of metallographic polishing and mounting machines, cold mounting consists of metallographic mounting powder and a metallographic curing agent. When mixed at room temperature and thoroughly stirred, the mixture cures within 15 minutes to form a transparent, rigid material that is ready for polishing and further processing. This material features low exothermic heat during curing, minimal thermal shrinkage, and excellent heat resistance, making it suitable for use in the electronics industry as a microchip mounting adhesive, as well as for cold mounting and sample preparation of various microstructural specimens.
Metallographic polishing and grinding machine manufacturers emphasize that the primary purpose of polishing is to visually reveal the true microstructure of the sample. The surface of the specimen to be examined is polished to a bright, flawless mirror finish, after which etching is employed to enable detailed analysis of the microstructural features. These manufacturers further note that the anti-adhesive platen of the polishing machine is coated with a special non-stick layer, allowing sandpaper or back-adhesive polishing cloths to be securely affixed; such attachments can be easily replaced without leaving any residual adhesive. Silicon carbide metallographic sandpaper is commonly used, typically in the form of wet sandpaper, and requires only water during the grinding process. Metallographic sandpaper is an essential step in both coarse and fine grinding during routine metallographic sample preparation. During grinding, careful observation should be conducted continuously. For polishing, a velvet cloth impregnated with diamond polishing compound or polishing paste is employed.
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