Hardening of steels requires that the material be heated to a high temperature followed by a quenching and tempering process. During the heating cycle, the room temperature phase is transformed into a face-centered cubic structure known as Austenite. During quenching, the Austenite will then transform into fresh Martensite, which is a very hard, but brittle phase. Thus, a tempering process is almost always undertaken to reduce the brittleness of the steel at the expense of a slight loss in hardness. In real life, however, the heat treeatment process is not as ideal as this. Often, some of the Austenite will be retained after quenching and tempering, which can lead to a degradation in the materials performance. This is due to the fact that the retained Austenite can be transformed into fresh, untempered Martensite by applied stresses while in use. Also, the transformation of the retained Austenite will cause a dimensional instability in the part, leading to QC problems.

We use the following sample preparation procedure:

1.) Cutting the sample with a water cooled abrasive disk. Cutting process must not damage or change the sample as this would lead to erroneous results.
2.) Sample mounting with cold or hot mounting method.
3.) Grinding samples on SiC papers with grit size of 180, 240, 320, 400 and 600.
4.) Mechanical polishing with 3 um diamond paste.
5.) 3 min electropolishing to remove interfering oxides and eliminate any plastically deformed surface layer.
6.) Specimens must be cleaned after each step, all grains from one grinding and polishing step must be completely removed from the specimen to avoid contamination, which would reduce the efficiency of the next preparation step. Clean, grease free surfaces are essential for subsequent chemical or electrolytic treatment. Residues, fingerprints, and inconspicuous films may interfere with etching, causing various areas to be attacked at different rates. Every single microsection preparation procedure must be followed by through cleaning, which can be performed in different ways. Rinsing is most frequently used and consists of holding specimen under a stream of running water and wiping the surafce with a soft brush or cotton swab. After cleaning, specimens may be dried rapidly by rinsing in alcohol, benzene, or other low-boiling-point liquids, then placed und a hot-air drier for sufficient time.