The microstructures of metallic materials have a direct influence on the technological properties, e.g. machinability, corrosion resistance, hardness and wear resistance. The diversity of materials and microstructures is characterized and compared with a wide range of standards and test procedures. The microstructures are predominantly classified with an image comparison or length measurements.
The grain size and grain alignment are decisive parameters for an evaluation of the mechanical – technological properties of a material.
Hereby, if possible, a material sample is taken lengthwise to the direction of rolling and is metallographically prepared. Subsequently the structure is made visible by a specific grain boundary caustic.
Under the light microscope the grain structure can be compared with indicatory series pictures and can be assigned to the corresponding grain size code.
Alternatively an ambulant sample preparation and structure etching can happen without destroying the component directly. For the light microscopical examination a structure mold with films is generated.
Normen: ASTM E 112, DIN EN ISO 643, AV 178
For the characterization of metallic, ceramic and organic layers and layer systems the layer thickness is an important parameter. With it, for example, the corrosion behavior , mechanical strength or the optics can be improved. Measuring the layer thickness happens in the metallographic specimen . Here you can perform any measurement variant from live measurements through an eyepiece to complex , automated image analysis.
Normen: DIN EN ISO 12345; DIN 1235, AV 1245
Cast irons are very important ferrous materials besides the steel. They are characterized by their good castability and machinability. The characteristic feature is the graphite phase. It has a decisive influence on the mechanical properties. Depending on the material, lammellar graphite (GG) globular graphite (GGG) or vermicular graphite (GGV) is distinguished.
The shape, size and arrangement of the graphite phase are evaluated with reference images. Thus a generally valid marking of the cast material can be created.
The purity of steel is defined by its nonmetallic inclusions. Inclusions such as oxides or sulfides represents a material separation because of their phase boundary. This can adversely affect the fatigue strength of highly stressed components.
A microscopic test is described in standard DIN 50602. A fixed sample area is analyzed for inclusion type, size and frequency. With a mathematical calculation, a characteristic value for the purity of the steel material is obtained.
Aluminum castings solidify predominantly dendritically. In order to characterize the microstructure, the secondary dendrite arm spacing is indicated. In the VDA P220 leaflet an analysis is determined how it is measured. Thus conclusions can be drawn about the solidification process.
Carbide plays an important role in hard iron materials. In steel, a wide variety of materials can be created from tough to brittle. This is achieved with heat treatments and carbide formation. Mechanical engineering uses this for transmissions and rolling bearing technology.
In the test instructions SEP1520, the shape, arrangement, size and proportion of the carbides are analyzed by microscopy. Thus, steel qualities can be defined and tested.