Thermophysical properties and microstructure of 32CrMoV12-28 hot-work tool steel

Measurements of thermal diffusivity, heat capacity and thermal expansion of hot work tool steel 32CrMoV12-28 have been carried out in the temperature range from room temperature (RT) to 1000℃. 32CrMoV12-28 steel has been tested for military applications as steel for gun barrels. The thermophysical properties of this steel can be used as input data for numerical simulations of heat transfer in gun barrels. Both the LFA 427 laser flash apparatus in the RT1000℃ temperature range and the LFA 467 light flash apparatus in the RT500℃ temperature range were used for thermal diffusivity tests. Specific heat capacity was investigated in the range RT1000℃. The specific heat was determined by two methods, i.e. the classical method, the so-called continuous-scanning method and the stepwise-scanning method according to EN ISO 11357-4. The paper compares both methods and assesses their suitability for testing the specific heat capacity of barrel steels. Thermal expansion was investigated in the range RT1000℃. Inconel 600 was selected as the reference material during the thermal diffusivity test using LFA 467. Light microscopy (LM), scanning electron microscopy (SEM), and Vickers microhardness measurements were performed to detect changes in the microstructure before and after thermo-physical measurements. We compared the results of measurements of the thermophysical properties of 32CrMoV12-28 steel with the results of our tests for other barrel steels with medium carbon content, i.e. X37CrMoV5-1 (1.2343), 38HMJ (1.8509) and 30HN2MFA. The comparison was made in terms of shifting the effect of material shrinkage towards higher temperatures.