How do hot-mounting consumables ensure the accuracy and stability of metallographic sample preparation?- Trojan (Suzhou) material technology Co., Ltd.

How do hot-mounting consumables ensure the accuracy and stability of metallographic sample preparation?

24-04-2025

Hot-mounting consumables are mainly divided into two categories: thermosetting resins and thermoplastic resins. Thermosetting resins undergo cross-linking polymerization chemical reactions under heating and pressure to form irreversible solidified structures. Taking phenolic resin as an example, it has the characteristics of low cost, diverse colors, and short curing time, which is very suitable for rapid sample preparation and multiple sample comparison experiments. Its structure after curing is stable and can effectively support the sample to prevent deformation or damage during subsequent grinding and polishing.

Epoxy resin is also a thermosetting resin. It has edge retention and adhesion capabilities, and can provide good protection and support for the edges of coatings or precision samples. Moreover, epoxy resin has good corrosion resistance to strong corrosive agents and solvents as well as heated corrosive agents, which can ensure the stability of samples in complex environments.

Thermoplastic resins only undergo physical changes, gradually softening and melting at high temperatures, and hardening when cooled. Acrylic (acrylic resin) is a common thermoplastic resin. Unfilled acrylic glue has transparency and can well observe the state of the sample. However, its hardness is relatively low and its shrinkage rate is average. The characteristics of thermoplastic resin make it suitable for pressure-sensitive samples, and damage to the sample can be avoided during the heating and softening process.

Universal resin uses conventional reinforcing fillers, has good rheology, moderate hardness, and is relatively economical. It is the most widely used hot mounting resin. It can meet the mounting needs of most conventional samples, provide basic support and protection for the samples, and ensure the smooth progress of the sample preparation process.

The reinforcing filler of edge-preserving resin is a harder and more wear-resistant mineral fiber with high hardness and good wear resistance. When grinding and polishing with harder samples, better material synchronous removal can be achieved, effectively avoiding the rounding phenomenon of the edge, and ensuring the accuracy of focused observation at the same depth of field. However, the rheology of this resin is relatively poor, and higher pressure is required to achieve tight filling during mounting, and a hydraulic mounting machine is usually required to complete the operation.

Functional resins are designed for special needs, such as conductivity and transparency. Conductive hot-mounting materials (black) contain graphite fillers and have conductivity. They are mainly used in areas that require high conductivity, such as electron microscope scanning. During the electron microscope scanning test, it can ensure that the sample has almost no voltage loss (less than 0.5%), providing a guarantee for accurate microstructure analysis. Transparent hot-mounting materials (such as acrylic + inorganic fillers) are convenient for observing the sample state and are suitable for scenes that require sample transparency.

Hot-mounting consumables can firmly wrap irregularly shaped and difficult-to-take tiny samples to form a stable whole. In the subsequent grinding and polishing process, the consumables can effectively prevent the sample edge from cracking and falling off, avoid the sample from being disturbed by external factors, and ensure the integrity of the sample and the retention of the original structure.

Different types of hot-mounting consumables have different shrinkage rates and hardness. Choosing the right consumables can control the size changes during the sample preparation process, ensuring that the size of the mounted sample is stable and meets the analysis requirements. For example, epoxy resin has a very low shrinkage rate, which can ensure that the size of the sample changes very little after mounting, providing a reliable basis for accurate size measurement and microstructure analysis.

Edge-preserving hot mounting materials and epoxy resins with good edge retention ability can effectively protect the edge of the sample during grinding and polishing to avoid chamfering or damage to the edge. This is crucial for observing the microstructural characteristics of the sample and can ensure the accuracy and reliability of the observation results.

Hot mounting consumables have good chemical stability and are resistant to general acids/alkalis/salts/mineral oils and low-grade alcohols. During sample preparation and subsequent analysis, it can effectively prevent the sample from being corroded by chemical substances, ensure that the chemical composition and microstructure of the sample do not change, and ensure the accuracy of the analysis results.

Key points for hot mounting consumables
Before hot mounting, the sample must be thoroughly cleaned to remove dirt and oil on the surface of the sample. It can be cleaned with solvents such as DI water, alcohol or acetone, and ultrasonic cleaning can be used if necessary. After cleaning, dry the sample to ensure that the sample surface is clean and dry to improve the bonding strength between the consumable and the sample.

According to different types of hot mounting consumables, reasonably set parameters such as mounting pressure, temperature and time. For example, for red, white, black and green phenolic resin mounting materials, the mounting pressure is generally 30±5MPa, the mounting temperature is 135±5℃, the mounting time is 10-15 minutes, and the cooling time is 10 minutes. For transparent hot mounting materials, the mounting temperature needs to be increased to 170±5℃, and the mounting time is extended to 15-20 minutes. Accurate parameter settings can ensure that the consumables are fully cured and form a stable mounting structure.

After the mounting is completed, use a suitable demolding agent for demolding to ensure that the sample can be smoothly removed from the mold while avoiding damage to the sample and the mold. For some special hot mounting materials, such as very hard epoxy mounting materials, it is recommended to use a special demolding agent and demold according to the correct operating method.