Roentgenographic determination of the residual austenite proportion as a quality assessment for implemented heat treatment or as a conformity test as to whether a specified residual austenite threshold value was complied with.
After the hardening or case hardening, the material can still contain residual austenite (RA) – an austenite that has not converted into martensite and is still present at room temperature.
In general, residual austenite is undesired, as it is very soft and, under certain circumstances, can convert into martensite at a later time. High proportions of residual austenite reduce wear resistance and dimensional stability significantly and they increase the risk of grinding cracks.
For this reason, knowledge of the residual austenite content is extremely important in many cases. The X-ray diffractometer analysis (RDA, XRD) has established itself over many years as a process for determining the residual austenite content according to ASTM E 975-13, as it is significantly more reliable, more accurate and more meaningful than a purely optical estimate using a light microscope.