Metallographic

Metallography is the study of the physical structure and components of metals, typically using microscopy.
Metallographic, micrographic and macrographic inspections are among the most important analytic techniques to evaluate the characteristics of metallic materials.

Indeed, the structure strongly affects the properties of the material. These tests do not result in figures as they are inspections (by the microscope, the stereomicroscope or visual). Therefore, the skills and experience of the technician are basic for the success of the inspection and for obtaining as much information as possible from that inspection.

The connection between the structural constituents found out, the defect causes these could have determined on the examined sample, the actions to implement in the production cycle to avoid the repeated occurrence of the defect etc., are considerations requiring a deep metallurgic knowledge and a long lab experience.

Micrographic inspections
Micrographic metallographic inspections are widely used in the analysis aimed at determining the structural state of the concerned sample.
As a matter of fact, the structure strongly affects the mechanical characteristics of the material, thus the great interest in this kind of tests. There are countless applications ranging from the determination of the supply status of a rolled section to the study of the failure of a mechanical component.
It is kind of analysis, the deep knowledge and experience of the technician play a very big role.

Scanning electron microscope (SEM) inspections
The electron microscope can enlarge the observed image till 300,000 times, making highly accurate investigations possible.
For example, the SEM gives a decisive contribution in studying the failure surfaces of mechanical parts (fractograph). Moreover, used with the energy dispersion sound, it allows chemical analysis in extremely limited areas. In this way, after having found out an inclusion or a corrosion product of a few micron, you can carry out its chemical analysis and determine its composition and thus its origin.
Obviously, it is an extremely powerful and versatile instrument, which becomes completely useless if not used by a highly experienced technician in this field.

Macrographic inspections
These are carried out by a stereomicroscope, a special instrument allowing observation with a certain number of magnifications without losing the depth of the field of view, thus keeping a three-dimensional view of the object.
Macrographic inspections have several applications: from the study of the fracture surfaces (search for failure causes of mechanical parts) to the observation of a welded structure, to the survey of sulphur and lead distributions (Bauman impression and Wragge impression) in certain steels.


 
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