Tempering effects on a martensitic high carbon steel

We study the effect of tempering on a martensitic steel containing 1.23 wt.% carbon, in the temperature range 300–800 K, correlating the results obtained by measurements of thermoelectric power (TEP), Young’s modulus, calorimetry, nanoindentation, and the observations by transmission electron microscopy (TEM). Two tempering stages are observed, one between 350 and 430 K, and the other between 470 and 550 K. They are attributed to two stages of carbon precipitation. The evolution of Young’s modulus, TEP, and hardness is mainly attributed to the change of the amount of interstitial carbon in iron.