Metallographic Mounting Selecting 2025｜5 Key Considerations

Metallography is a science that uses laboratory equipment to study the internal structure of metals and their alloys. It plays a crucial role in materials science and engineering.

Through metallographic analysis, researchers can observe microstructural features such as grain structures, phase compositions, and defect distributions within metals using laboratory equipment. This information is vital for evaluating material performance, diagnosing failure causes, and developing new materials. However, obtaining high-quality metallographic images relies on meticulous sample preparation, which directly impacts subsequent analysis results.

Metallographic mounting is a critical step in the pre-treatment process, usually performed after cutting. After cutting, samples are often too small, fragile, or contain pores and cracks, making them difficult to handle during the grinding and polishing stages that follow.

Mounting the sample is essential to ensuring smooth progress in the preparation process. Below are the primary reasons for metallographic mounting:

1. Sample size is too small: When the sample is too small to be hand-held for grinding and polishing, mounting allows for easier handling and processing using laboratory equipment.

2. Fragile samples: For fragile samples with pores or cracks, metallographic mounting provides protection, preventing further damage during subsequent experiments.

3. Achieving good edge retention: Metallographic mounting ensures the integrity of the sample’s edges, preventing material loss during grinding and polishing, which results in more accurate analysis.

4. Compatibility with automatic grinding and polishing machines: Mounted samples can be more easily placed into automatic grinding and polishing machines, increasing efficiency and ensuring consistent results.

Additionally, mounting samples helps metallography personnel better secure the sample, providing a flat and stable surface, which is particularly important for precise analysis using other laboratory equipment.

The metallographic mounting process involves cleaning the sample, removing surface contaminants and oxidation layers, and ensuring the sample surface is free from contamination. The sample is then placed in a Cold Mounting Mold or a Hot Mounting Press, depending on the sample's characteristics, to select the appropriate mounting material.

Metallographic mounting is an indispensable step in the pre-treatment preparation process, aiming to protect and secure the sample, making it easier to handle during subsequent grinding and polishing stages.

Metallographic mounting techniques can generally be divided into two types: metallographic cold mounting and metallographic hot mounting.

For samples that cannot withstand high temperatures and pressures, such as resistors, passive components, and other non-metal electronic parts, metallographic cold mounting is typically used to encapsulate and process these samples.

For samples that can withstand high temperatures and pressures, metallographic hot mounting is used to prepare them for further laboratory equipment processing.

1. Metallographic Cold Mounting

Metallographic cold mounting involves encapsulating the sample in resin through a chemical reaction. The primary materials used are epoxy resin and hardener, which, when mixed, undergo a chemical reaction and gradually harden, making the sample suitable for subsequent laboratory equipment applications.

The advantages of this method include:

(1) Suitable for non-metal samples

Metallographic cold mounting is ideal for fragile, sensitive, or heat-sensitive non-metal samples such as ceramics, plastics, and biological materials.

(2) Low-temperature operation

Since metallographic cold mounting is performed at room temperature, it avoids the effects of high temperatures on the sample, making it particularly suitable for materials sensitive to temperature.

(3) Simple operation

The metallographic cold mounting process is relatively simple. The sample is placed in a mold, mixed epoxy resin and hardener are poured over it, and once hardened, the sample is ready for further laboratory equipment applications.

2. Metallographic Hot Mounting

Metallographic hot mounting uses high temperature and pressure to compress and form the sample.

Common metallographic mounting materials include bakelite powder and acrylic powder. The advantages of this method include:

(1) Suitable for metal samples

Metallographic hot mounting provides higher pressure and temperature, ensuring a strong bond between the metal sample and the mounting material. It is suitable for mounting metal and alloy samples for subsequent laboratory equipment applications.

(2) Short pre-treatment preparation time

Due to the high temperature and pressure used in metallographic hot mounting, the preparation time is shorter, typically completed within 20 minutes, making it ideal for large-scale, fast sample mounting.

(3) High strength

Metallographic hot mounting materials usually have high strength and hardness, providing stable support, especially suitable for high-strength operations with other laboratory equipment.

Mounting the sample provides a flat surface, protects the edges of fragile samples, and ensures that the sample remains intact during grinding and polishing processes.

Controlling the porosity and achieving good edge retention during the mounting process enhances the accuracy and consistency of the analysis results. Mounted samples are also well-suited for automated grinding and polishing machines, improving experimental efficiency.

In summary, metallographic cold mounting and metallographic hot mounting each have their advantages. The appropriate method should be selected based on the sample's characteristics and the requirements of the metallographic laboratory equipment, ensuring smooth pre-treatment preparation and precise final analysis results.

Metallographic mounting machines can be divided into two main categories: metallographic hot mounting machines and metallographic vacuum cold mounting machines.

1. Metallographic Vacuum Cold Mounting Machine

In the metallographic preparation process, metallographic vacuum cold mounting is a critical step. It is widely used in the preparation of various materials as it preserves the original state of the sample.

However, the cold mounting process often encounters issues with air bubbles, which can cause voids or cracks during grinding and polishing, thereby affecting the accuracy of metallographic analysis.

To solve this issue, laboratory equipment like metallographic vacuum cold mounting machines was developed.

When processing samples such as ICs, resistors, PCB boards, and other non-metal components that cannot withstand high temperatures and pressures, the mixing of resin and hardener can generate air bubbles.

If these air bubbles are not effectively removed, they can impact the results of subsequent experiments. Vacuum cold mounting machines effectively remove bubbles from the resin, ensuring the sample's integrity and the accuracy of observations.

The metallographic vacuum cold mounting technique relies on the negative pressure environment within the vacuum chamber to remove air bubbles.

Vacuum cold mounting machines use vacuum technology to effectively remove air bubbles from both the sample and the embedding resin, ensuring the resin penetrates the fine gaps in the sample.

This not only improves the quality of the mounting but also enhances the reliability of subsequent metallographic experimental analysis.

The process of removing air bubbles with a vacuum cold mounting machine is as follows:

(1) Place the mixed resin and hardener into the vacuum chamber during operation.

(2) The vacuum pump extracts the air from the chamber, causing the bubbles in the resin to expand and rise to the surface.

(3) As the pressure decreases further, the bubbles burst and are removed.

(4) Repeated cycles of vacuum and release thoroughly remove the air bubbles within the resin, ensuring the sample's stability and the precision of other laboratory equipment testing.

Metallographic vacuum cold mounting can also handle porous samples:

(1) Porous sample structures are complex, and bubbles tend to remain in tiny pores. Traditional bubble removal methods are ineffective, but vacuum cold mounting effectively solves this problem, making observation with other laboratory equipment easier.

(2) The vacuum cold mounting technique uses pressure differences to extract bubbles from the pores, ensuring no bubbles remain inside the sample, improving the processing efficiency and observation quality of other laboratory equipment.

Next, we will introduce the structure and operation of the metallographic vacuum cold mounting machine in detail, along with its applications in various fields, and explore its importance in metallography.

The metallographic vacuum cold mounting machine consists of several key components, each playing an important role in achieving an efficient mounting process. These components mainly include the vacuum pump, mounting mold, and control panel. Below is a detailed introduction of these components and their functions.

(1) Vacuum Pump

The vacuum pump is the core of the metallographic vacuum cold mounting machine, and its primary function is to lower the pressure inside the cold mounting mold, creating a vacuum environment.

(2) Cold Mounting Mold

The mounting mold of the vacuum cold mounting machine is the container where the sample and resin are placed, typically made of pressure-resistant materials to ensure no deformation or leakage under vacuum conditions.

The size and shape of the mold can be selected according to the sample's dimensions to maximize mounting efficiency and sample quality.

(3) Control Panel

The control panel is the primary interface for operating the vacuum cold mounting machine. It can be divided into traditional and LCD panels, allowing users to set parameters such as vacuum level, duration, and pressure.

Traditional panels use manual switches to control the vacuum level and time, while LCD panels allow for preset parameters, achieving automation.

The main functions and features of the metallographic vacuum cold mounting machine include the following:

(1) Vacuum Bubble Removal Function

Vacuum bubble removal is the most basic and essential function of the vacuum cold mounting machine. By reducing the pressure inside the cold mounting mold, bubbles are more easily released. This is especially important for porous materials and complex sample structures, facilitating observation with other laboratory equipment.

(2) Ease of Operation

Most vacuum cold mounting machines have a simple operation process. Most settings can be completed via the control panel. Users only need to place the sample, set the parameters, and activate the vacuum cold mounting machine.

(3) Improved Mounting Quality

Due to the vacuum technology in the vacuum cold mounting machine, bubbles are effectively removed from the epoxy resin. The final mounted sample exhibits better uniformity and integrity. When observing the microstructure with other laboratory equipment, a clear and bubble-free sample provides more accurate and reliable data.

(4) Wide Applications

Vacuum cold mounting machines are suitable for the pre-treatment of a wide range of materials, including metals, ceramics, composites, and electronic components. This technique is especially advantageous when dealing with fragile or complex samples, making them easier to detect with other laboratory equipment.

The operational steps of a vacuum cold mounting machine typically include sample preparation, resin selection and preparation, vacuum mounting steps, sample curing, and metallographic analysis. Each step is explained in detail below.

(1) Sample Preparation

Before mounting, the sample needs to be cleaned to remove surface oils, dust, or other contaminants that may affect the mounting process. The size and shape of the sample should match the cold mounting mold to ensure uniform resin coverage.

(2) Resin Selection and Preparation

The choice of cold mounting resin depends on the sample properties and analysis requirements. Common resin materials include epoxy resin and acrylic resin. The resin must be mixed according to the manufacturer’s recommended ratios to ensure stable post-curing performance and compatibility with other laboratory equipment.

(3) Vacuum Cold Mounting Operation Steps

Place the prepared sample into the cold mounting mold and add an appropriate amount of cold mounting resin. Activate the vacuum cold mounting machine, set the appropriate vacuum level and duration, and let the machine work.

Maintain the vacuum for a period to allow the resin to fully penetrate the sample’s fine pores, removing all bubbles.

(4) Sample Curing and Metallographic Analysis

After the vacuum process is complete, turn off the vacuum pump and allow the sample to cure at ambient pressure. The curing time depends on the resin type and ambient temperature. Once curing is complete, the sample can be removed and processed further on other laboratory equipment for metallographic analysis.

Currently, there are two types of vacuum cold mounting machines available: manual and automatic. Below is a comparison of both types and their applications:

(1) Manual Vacuum Cold Mounting Machine

Manual vacuum cold mounting machines require the operator to manually vacuum and release pressure. Although more labor-intensive, they are cost-effective and suitable for small-scale or specific laboratory and production environments. For example:

 Saving on the purchase cost of vacuum cold mounting machines

 Suitable for handling a small number of samples

 Flexible for various specific needs

(2) Automatic Vacuum Cold Mounting Machine

Automatic vacuum cold mounting machines complete the vacuum and pressure release process automatically, significantly reducing labor costs and operation time. They are suitable for high-volume sample processing or efficient production applications. For example:

 Reducing manpower

 Improving efficiency

Regardless of whether it is manual or automatic, vacuum cold mounting technology plays a critical role in modern materials science, electronic manufacturing, and scientific research. By removing bubbles, it ensures material quality and performance stability, improving the accuracy of laboratory equipment testing.

(1) In materials science, it is used for pre-treating porous materials to prevent observation inaccuracies in other laboratory equipment.

(2) In electronic manufacturing, it is suitable for samples that cannot withstand high temperatures and pressures, such as ICs, resistors, and PCB boards, solving the difficulties encountered in other laboratory equipment observations.

(3) In scientific research, it is used for sample preservation and analysis.

These techniques significantly enhance experimental and production efficiency and quality by optimizing sample edge protection and resin penetration, allowing the sample to be tested smoothly with other laboratory equipment.

By effectively removing bubbles during the mounting process, vacuum cold mounting machines significantly improve the uniformity and integrity of the samples, enabling more precise observations on other laboratory equipment, thereby enhancing the accuracy of metallographic analysis.

As materials science and engineering technology continue to advance, the application prospects for laboratory equipment like vacuum cold mounting machines will broaden. Whether in material research or industrial production, choosing the appropriate vacuum cold mounting machine is essential for ensuring product quality and improving research results with other laboratory equipment.

2. Metallographic Hot Mounting Machine

Metallographic hot mounting technology plays an indispensable role in modern materials science and metallographic analysis, particularly suitable for samples that can withstand high temperatures and pressures without easily cracking, such as steel and brass.

This technique primarily uses high temperatures and pressures, embedding samples with bakelite powder or acrylic powder to protect the edges and surface defects of the samples during metallographic pre-treatment, ensuring that the samples are not damaged and that their detection with other laboratory equipment is not affected.

Pressure and Mold Tube Size Effects

The pressure applied to the sample inside the mold tube is greatly influenced by the force exerted by the hydraulic cylinder and the size of the mold tube.

There are many types of metallographic hot mounting machines in laboratory equipment, and it is important to choose the right equipment based on different usage needs and budgets. Below is a detailed introduction to manual pressure compensation, automatic pressure compensation (fixed pressure), and automatic pressure compensation (adjustable pressure) features:

(1) Manual Pressure Compensation (Product: ML-MAI)

 Target Users: Users who require economical laboratory equipment or have pressure-sensitive samples.

 Operation: During the sample heating process, manual pressure compensation is used to shape the sample.

 Advantages: Lower cost, suitable for budget-conscious users, high flexibility, and the ability to manually adjust pressure according to sample needs.

(2) Automatic Pressure Compensation (Fixed Pressure) (Product: ML-C)

 Target Users: Laboratory equipment users who need to save time and do not have high pressure requirements.

 Operation: The machine automatically performs the pressurizing and cooling processes without manual intervention.

 Advantages: Fully automatic operation, simple to use, even for users unfamiliar with mounting machines, saving time and labor with higher efficiency.

(3) Automatic Pressure Compensation (Adjustable Pressure) (Products: ML-L1A/ML-L2)

 Target Users: Professional users of laboratory equipment who need a variety of pressure adjustment options.

 Operation: During the mounting process, the machine automatically completes pressurization and cooling, with adjustable pressure settings to meet different sample needs.

 Advantages: Adjustable pressure, wide range of applications, able to handle high-temperature and pressure-sensitive samples; parameters can be freely adjusted according to different materials, bakelite powder types, and pre-treatment needs to ensure the quality of metallographic pre-treatment and the applications of subsequent laboratory equipment.

Some laboratory equipment on the market, such as metallographic hot mounting machines, also come with a preheating mode. The preheating mode can significantly shorten the hot mounting time, and its functions and advantages are as follows:

(1) Shorten Mounting Time

The preheating mode can preheat the samples and materials in advance, shortening the heating time during the curing process, thereby improving overall preparation efficiency and optimizing the processes of other laboratory equipment.

(2) Uniform Temperature Distribution

Preheating also ensures uniform temperature distribution in the samples and mounting materials, further improving curing quality and increasing the processing efficiency of other laboratory equipment.

(3) Enhance Sample Stability

Preheating helps to fully protect the edges and surface defects of samples during the pre-treatment process, reducing stress and potential cracks caused during the cooling phase, and minimizing errors in observation with other laboratory equipment.

The selection of consumables differs between metallographic cold mounting and hot mounting. Metallographic cold mounting typically uses epoxy resin and hardener to solidify the sample, while hot mounting uses bakelite powder to encapsulate the sample. Choosing the right laboratory equipment ensures the accuracy and efficiency of the results.

1. Metallographic Cold Mounting

Metallographic cold mounting generally uses resin and hardener, which harden through chemical reactions. In such cold mounting operations, suitable laboratory equipment, such as vacuum cold mounting machines, can help remove bubbles and improve the quality of the sample.

The surface hardness of cold-mounted samples is usually lower, so when grinding and polishing harder samples (such as tungsten carbide), it is important to select the appropriate consumables and laboratory equipment to avoid excessive wear of the resin around the sample and to prevent the sample itself from not being properly ground (a phenomenon known as edge relief).

TopTech offers several types of cold mounting resins, including:

(1) Fast-Curing Epoxy Resin (Product: S0303A-1)

 Curing time: Approximately 45 minutes

 Odor: Strong

 Advantages: Competitive price and faster curing time

 Note: Most bubbles cannot be removed through the vacuum mounting process

(2) Acrylic Resin (Product: S0303A-3)

 Curing time: Approximately 10 minutes

 Odor: Strong

 Advantages: Faster curing time

 Note: Most bubbles cannot be removed through the vacuum mounting process

(3) High-Flow Epoxy Resin (Product: S0303A-2)

 Curing time: Approximately 24 hours

 Odor: None

 Advantages: Can remove most bubbles through the vacuum mounting process, resulting in a clear sample after curing

 Note: Longer curing time

Precautions When Using Cold Mounting Resin

(1) Handling Technique

When pouring epoxy resin and hardener, a stirrer should be used to pour the mixture slowly along the edge of the mixing cup to avoid generating too many bubbles before stirring.

(2) Stirring Method:

Stirring should be done in a consistent direction and speed to avoid introducing excess bubbles during the stirring process.

(3) Pouring Method:

After mixing the resin and hardener, pour the mixture slowly into the silicone mold cup using a stirrer. Alternatively, laboratory equipment such as vacuum cold mounting machines can be used to slowly draw the liquid along the edge of the silicone mold cup to minimize bubble formation. This type of equipment significantly improves the quality and efficiency of cold mounting.

When purchasing cold mounting resins, note any export and import restrictions. Always verify the Material Safety Data Sheet (MSDS) with the supplier to ensure compliance with legal import/export requirements.

2. Metallographic Hot Mounting

In the hot mounting process, common materials include bakelite powder and acrylic powder. Each of these materials has its characteristics and applications. Combined with appropriate laboratory equipment such as hot mounting presses, safe and efficient operation at high temperatures and pressures can be ensured.

(1) Bakelite Powder

There are two main types of bakelite powder: general bakelite powder and conductive bakelite powder. Bakelite powder, also known as phenolic resin, is characterized by its high-temperature resistance and non-absorbent properties, making it suitable for most metallographic analysis applications.

The preparation of bakelite powder is usually completed in about 15 minutes, including cooling time. While different brands may have slight differences in hot mounting parameters, the overall process remains largely the same.

 General Bakelite Powder: Suitable for general metallographic hot mounting, offering good edge protection and moderate shrinkage. It is an economical choice but requires specialized laboratory equipment for proper handling.

 Conductive Bakelite Powder: Ideal for samples requiring observation via SEM (Scanning Electron Microscope). Conductive bakelite powder ensures proper conductivity during metallographic pre-treatment, resulting in clear imaging and accurate analysis. SEM observation also relies on efficient laboratory equipment for successful execution.

(2) Acrylic Powder

Acrylic powder has transparent molding properties, making it suitable for metallographic tests requiring deep grinding, and the resulting samples are clear, allowing for easy metallographic examination.

The hot mounting time for acrylic powder is slightly longer, around 20 minutes, including cooling time. Different brands may have variations in hot mounting parameters, such as pressure, temperature, heating time, and cooling time. Professional laboratory equipment ensures precise control over each parameter.

Tested acrylic powder ensures the production of samples with the highest transparency, which is particularly important for metallographic tests requiring deep grinding observations and analysis. Using appropriate laboratory equipment and accurate parameter control greatly enhances the quality of transparent samples.

After curing, acrylic powder produces highly transparent samples, allowing for clear observation during the metallographic grinding and polishing process, preventing over-grinding, and maintaining the flatness and integrity of the sample surface.

Bakelite powder and acrylic powder have fewer export and import restrictions compared to epoxy resin and hardener. However, it is still recommended to request the Material Safety Data Sheet (MSDS) from the manufacturer before export to avoid any issues during the import/export process.

3. Sample Clamps

In metallographic analysis, samples that are too thin after cutting may not be able to stand on their own, requiring the use of sample clamps for stabilization and securing.

Specifically, plastic circular sample clamps are often used during the cold mounting process. These clamps can easily hold thin and small samples, ensuring stability during the mounting process.

Conversely, stainless steel circular sample clamps are more suitable for the hot mounting process. Due to their high-temperature and pressure resistance, these clamps provide strong support during the hot mounting process, maintaining the sample’s shape and stability.

Using the appropriate sample clamps ensures the safety and stability of the sample during the mounting process and improves the efficiency and accuracy of subsequent grinding, polishing, and other steps. Therefore, choosing the right sample clamps based on different mounting methods and sample characteristics is a critical step.

Throughout the entire metallographic analysis process, equipment such as cold mounting presses, hot mounting presses, and vacuum cold mounting machines play a key role. These laboratory equipment not only enhance the quality of the mounting but also significantly improve operational efficiency.

Purchasing a metallographic mounting machine is a significant equipment investment, whether in materials science research, electronics manufacturing, or other fields involving metallographic analysis. Careful consideration of the various costs related to the equipment is essential.

These costs are not limited to the purchase price of laboratory equipment but also include operational, maintenance, and other hidden costs. Below is a discussion of the costs that may be involved before and after purchasing a metallographic mounting machine.

1. Equipment Purchase Costs (1) The Price of the Laboratory Equipment Itself

The purchase cost of a metallographic mounting machine is usually the first step in the investment. Depending on the functions, brand, and technological level of the laboratory equipment, the price may vary significantly. Different types of laboratory equipment, such as metallographic hot mounting presses and metallographic vacuum cold mounting machines, have varying costs.

The initial cost of metallographic cold mounting is relatively low. If the consumer does not have special requirements for removing bubbles from the resin mixture, purchasing epoxy or acrylic resin is typically sufficient.

For metallographic hot mounting, both a hot mounting press and consumables must be purchased to proceed with the process.

(2) Training and Operation

To ensure the laboratory equipment operates correctly and efficiently, operator training costs are also an important expense. Manufacturers often provide training services, but these services may come at an additional cost. High-quality laboratory equipment often comes with more professional training services to ensure proper operation.

2. Operating Costs (1) Consumable Costs

In the metallographic mounting process, the consumption of consumables is one of the main daily operating costs.

For metallographic cold mounting, epoxy resin and hardener need to be purchased, while metallographic hot mounting requires the use of bakelite powder or acrylic powder. The amount of consumables used is directly related to the workload of the laboratory equipment.

Additionally, the use of sample clamps also incurs costs, as these clamps are considered consumable laboratory equipment accessories.

(2) Operation Time and Labor Costs

Manual metallographic mounting machines usually require more time and labor, meaning higher labor costs.

On the other hand, laboratory equipment with a higher degree of automation reduces manual labor, but the maintenance and calibration of the equipment still require professional technicians, which increases costs. For high-volume sample processing, the cumulative effect of time and labor costs becomes particularly significant. Therefore, choosing efficient laboratory equipment can reduce these hidden costs.

Metallography plays a crucial role in the fields of materials science and engineering, and metallographic mounting technology is an indispensable part of metallographic pre-treatment. Whether it is metallographic cold mounting or hot mounting, each has its unique application scenarios and technical advantages. Choosing the right laboratory equipment can greatly enhance the effectiveness of metallographic mounting.

Metallographic cold mounting is particularly suitable for handling fragile, heat-sensitive, or small samples. When paired with laboratory equipment such as vacuum cold mounting machines, it can effectively remove bubbles and improve the quality of the mounted sample.

On the other hand, metallographic hot mounting technology is more appropriate for samples that can withstand high temperatures and pressures, providing greater mounting strength and efficiency.

By selecting the appropriate metallographic mounting technique and laboratory equipment, choosing the correct consumables based on the sample's characteristics, and using suitable sample clamps, you can ensure the integrity and stability of metallographic samples, significantly improving the accuracy and reliability of subsequent metallographic analysis.

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