Jominy specimen

Test piece for determining hardenability by means of the end-quench test according to W. E. Jominy (DIN EN ISO 642).

The Jominy test is a standardized test procedure for assessing the hardness of a material. It consists of heating a standardized specimen having a diameter of ø 25mm and a length of 100mm to the austenitization temperature of 980–1010°C and then cooling it using a standardized water jet directed at one end (end-quench test). After cooling, hardness is measured starting from the quenched end (Fig. 1). This is primarily based on the HRC and HV 30 test methods (see Hardness test).

The differences in hardness along the test surface result from the various micro-structures produced by the differing cooling rates during the end-quench test. The cooling rate increases as the distance to the end surface decreases.

  • Fig. 1: Left: end-quench test (schematic); right: change in hardness (schematic and greatly enlarged, source: Wikipedia, Cdang)