Determination of martensite start temperature using an electromagnetic nondestructive technology

Assessment of martensite start temperature in alloy steels is of critical importance for many industrial applications of hardenable steels. To determine this, dilatometry is often carried out by characterizing the volume changes in the sample during cooling from austenitizing temperature. The method is destructive and costly, thus, is not normally utilized in quality inspection of the heat treated parts in the related industries. In the present paper, an electromagnetic technique has been explored to be utilized as a nondestructive tool to determine martensite start temperature in AISI D2 cold work tool steels. To detect the temperature, a designed NDE method was applied during cooling (from about 450 °C to 25 °C) of the samples austenitized in a range of 1000-1150 °C. The results show an acceptable accuracy of the proposed nondestructive method in comparison to the dilatometry as well as Andrew empirical equation in determining Ms temperatures.