Effects of Quenching Process on Microstructure and Properties of Powder Metallurgy High Carbon and High Chromium Mold Steel

The u se of powder metallurgy process to prepare mold steel can significantly refine the carbide size, and prolong its service life. The effects of quenching process on the microstructure and mechanical properties of powder metallurgical high-carbon and high-chromium mold steel were studied. Results show that, after quenching between 900-1200℃, with the increase of quenching temperature, the volume fraction of（Fe, Cr, Mo, V）₇C₃ phase decreases and the volume fraction and morphology of（Nb, V）C phase do not change much. The matrix gradually changes from ferrite to martensite, and the matrix hardness increases, while the residual austenite volume fraction increases.After quenching at 1150 ℃ and the following low-temperature tempering process, the hardness reaches 60 HRC, with the impact energy of 15 J, and the flexural strength of 2618 MPa. The volume fraction of（Fe, Cr, Mo, V）₇C₃ phase is 27.3vol% with an average size of 3 μm, whilst the volume fraction of（Nb, V）C phase is 2vol% with an average size of 0.5 μm.