Levan Engineering Ltd

I use a light microscope to examine fractures and microstructures for failure analysis and fitness for service. But the SEM is a more useful tool for many projects.

The SEM uses an electron beam instead of a light beam and magnifications up to 5000X are possible. The light microscope has a maximum magnification of 800X. The higher magnification of the SEM is useful to detect creep cavities and microstructure degradation, both of which occur at high temperature.

An example of using the SEM for in-situ metallography is included below. It would be difficult to determine if these are carbides or creep cavities at the grain boundaries if I had used a low magnification light microscope.

The SEM is also used to examine fractures. The surface features indicate the damage mechanism. Click on the image below of a cleavage fracture of a high carbon cast steel. The casting was brittle.

In-situ metallography of Incoloy 800HT pigtail after high temperature service. The microstructure consists of carbides at the austenite grain boundaries.