Effect of Tempering on Corrosion Properties of Mold Steel

Abstract

Abstract Proper heat treatment of mold steel is an effective way to improve its mechanical properties, but there are currently few research reports on the effect of heat treatment on the corrosion performance of mold steel. In this paper, the corrosion resistance of 3Cr17NiMoV mold steel after 500 °C tempering treatment was analyzed using Zeiss microscope, scanning electron microscope, laser confocal microscopy, 3.5 wt.% NaCl solution immersion experiment, electrochemical testing, and other research methods. The results show that after 500 °C tempering treatment, the microstructure of 3Cr17NiMoV mold steel is transformed from martensite to tempered sorbite, the inclusion is still Al2O3, and its size do not change significantly. After 500 °C tempering treatment, the corrosion rate of the sample increased from 9.56 mm/a to 12.75 mm/a, the area and depth of the pitting pits correspondingly increased from 1280.64 μm2 and 1.083 μm to 2115.08 μm2 and 1.818 μm, respectively. And the corrosion current density of the sample increases from 3.09×10−6 A/cm2 to 4.56×10−6 A/cm2. After 500 °C tempering treatment, the corrosion resistance of 3Cr17NiMoV mold steel was slightly reduced, so in engineering practice, it is necessary to carefully design heat treatment processes to balance mechanical properties and corrosion resistance.