False Porosity

Example: Superalloy after 5 min polishing, Mag. 500x.

Some materials have natural porosity, e.g.cast metals, spray coatings or ceramic. It is important to get the correct values, and not wrong readings because of preparation faults. Depending on the properties of a material, two contrary effects regarding porosity can be seen. Soft and ductile materials can be deformed easily. Therefore pores can be covered by smeared material. Hard, brittle materials often get fractured at the surface during the first mechanical preparation steps. Contrary to the ductile material, where the initial porosity seems to be low and the pores have to be opened, brittle materials seem to have a high porosity. The apparent fracturing of the surface has to be removed.

Reference: Metalog Guide, page 82-85, Struers A/S, 2610 Rodovre, Dennmark. Note: Image and text by courtesy of Struers A/S company.

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