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The entire process of metallographic sample preparation - from cutting to grinding and polishing, these details determine success or failure
2026-09-22
The accuracy of metallographic analysis results is directly related to the quality of sample preparation. Although some laboratories are equipped with high-end microscopes, it is still difficult to obtain clear metallographic structure diagrams, and the problem often occurs in the sample preparation process. Based on years of practical experience, LABTT has sorted out the technical details that need to be focused on in the entire process of metallographic sampling.
1、 Cutting: Control thermal effects and damage
Cutting is the first process of metallographic sampling, which aims to extract suitable samples for subsequent processing from large blocks of material. If the cutting is not done properly, the sample cutting surface may generate a heat affected zone and mechanical deformation layer, which will cause additional burden on the subsequent grinding and polishing process.
Key point 1: Adequate supply of coolant is required. The grinding heat during the cutting process is one of the main factors affecting the quality of the sample. The function of coolant is to timely remove heat and effectively control the temperature rise in the cutting area. It is necessary to ensure sufficient coolant flow and accurate spray angle, which can completely cover the cutting arc area and reduce the degree of thermal influence on the surface of the sample.
Key point 2: The selection of cutting consumables should match the material characteristics. For precision materials or hard and brittle materials, conventional cutting blades may cause significant cutting losses and damage layers. The ultra-thin diamond cutting blade has a small incision width and cutting resistance. When combined with the LABTT precision cutting machine, it can reduce the disturbance to the sample tissue during the cutting process.
2、 Mounting: solving the problem of clamping irregular samples
For samples with irregular shapes, small sizes, or requiring edge protection, mounting is a necessary preprocessing step. Reasonable selection of mounting methods and materials is helpful for the smooth progress of subsequent grinding and polishing processes.
Question 1: Selection of thermal sensitive material mounting. Traditional hot mounting has a high temperature, and some materials such as PCBs and coatings may be damaged. For this type of material, cold mounting can be used. The LUM series automatic light curing cold mounting machine adopts a low-temperature solidification mode, which can efficiently complete mounting and effectively protect thermal sensitive materials.
Question 2: Preventive measures for rounded edges. For surface coating, carburized layer or plated samples, edge rounding during grinding and polishing will directly affect the accuracy of thickness measurement. Choosing inlay materials with low shrinkage and high hardness, and controlling the pressure distribution during grinding and polishing, can reduce the occurrence of edge rounding.
3、 Grinding and polishing: removing damaged layers and controlling surface quality
The goal of the grinding and polishing process is to remove the damage layer introduced by cutting and rough grinding, and obtain a smooth, scratch free mirror surface. This stage has high requirements for operational standardization and process consistency.
Operation specification 1: Rotate the sample when replacing sandpaper. During the step-by-step grinding process with multiple layers of sandpaper, rotating the sample 90 ° for each finer sandpaper change can make the new and old scratches perpendicular to each other. This operation helps to determine whether the previous scratch has been completely removed under a metallographic microscope, thereby determining whether it can proceed to the next process.
Operation Specification 2: Application of Automatic Grinding and Polishing Equipment. A fully automatic grinding and polishing machine designed with a central loading force (such as the Naibo fully automatic metallographic grinding and polishing machine) can simultaneously fix multiple samples and maintain consistent stress states for each sample, which helps reduce batch differences introduced by manual operations and improve the consistency and repeatability of sample preparation.
In the process of metallographic sample preparation, cutting, embedding, grinding and polishing are interrelated, and the quality of the preceding processes directly affects the effectiveness of the subsequent processes. Standardizing and controlling details such as cutting cooling, embedding materials, and grinding and polishing techniques is a fundamental prerequisite for obtaining high-quality metallographic samples.
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