The analysis of microstructures, grain boundaries and layer thicknesses
Metallography is one of the most expensive processes in destructive materials testing. In metallography samples are taken from the material, ground, polished and etched. These preparatory steps are called sample preparation or sample preparation. In doing so, very careful attention is paid to not changing the initial properties and the structure of the material. Subsequently, the samples are digitally evaluated on the eyepiece of a microscope, on a screen or in the photo. There are three types of investigation in metallography. These are the structure investigation, the grain boundary determination and the layer thickness measurement. We offer all procedures and carry them out in our laboratory in Hasloch.
Why is metallography so important?
An important task of metallography is to find the connection between microstructure and properties of a material. An automatic structural characterization of cast iron is not feasible due to an irregular distribution and mixing of graphite particles. To facilitate the task for metallographers, the ideal cast iron structures with six different types of graphite were summarized in DIN EN ISO 945.
It has been proven that graphite type, shape, size and distribution have an influence on the properties of cast iron. However, the graphite type in cast iron with the same pearlitic matrix structure changes not only the mechanical but also the magnetic, electrical and thermal properties. Therefore, it is important to determine the volume fraction of individual graphite types and the size distribution of the graphite particles. The image analysis provides a reliable tool for this task and allows a characterization of the different microstructure types
Sample preparation at a glance
- Removal // a structural change is to be avoided
- Embed // for sharp cuts
- Grinding // to break down deformation layers
- Polishing // for a high surface quality
- Etching // to develop the structure
In microstructural investigations, specimens, either hot or cold embedded, are ground, polished and then etched into different grading stages. The microstructure made visible thereby provides information about the tempering and microstructure states – for example deformations, textures or victories – as well as other parameters such as contamination of the material.
Grain boundary determination
The grain boundary determination determines the grain sizes and their number in metallic materials. Among other things, the grain gives information about the strength and the corrosion properties of a metallic material. As in the microstructure analysis, specimens are ground, polished and etched for grain boundary determination. Then they are evaluated on the microscope, on a screen or in the photo.
Coating thickness measurement
The layer thickness measurement determines the thickness of different material layers in metallic materials. Similar to microstructural analysis, specimens are ground, polished and etched. Then they are evaluated on the eyepiece, on a screen or in the photo on the basis of the line cutting method or the circular cutting method.
We take over the transport
As with all destructive methods, we take over the entire transport of series. Thanks to our in-house vehicle fleet, we pick up the materials to be tested and return them after successful sampling.
Accredited for metallography
DIN EN ISO 945-1 2018-05 Cast-iron microstructure – Part 1: Graphite classification by visual evaluation