Effect of austenitizing temperature on microstructure transformation and properties of 40Cr2Ni4MoV steel

The selection of austenitizing temperature has a significant impact on the solid-state phase transformation of test steel. The microstructure transformation and properties of 40Cr2Ni4MoV steel at different austenitizing temperatures were investigated by analytical techniques such as quenching thermal dilatometer and laser confocal microscope. The results showed that as the continuous increase of austenitizing temperature, the microstructure gradually changed from a mixture of martensite and a small amount of bainite to all martensite. The undissolved carbides gradually changed from a few precipitations along the grain boundaries to a large number of precipitations, and eventually the precipitation mode developed into a combined precipitation at both grain boundaries and within the grains. The average hardness of samples also increased with the increase of austenitizing temperature. Therefore, under the condition of ensuring the microstructure and properties of 40Cr2Ni4MoV steel, the preferred austenitizing temperature was 920 ℃.