Effect of heat treatment on the grain size, microhardness and corrosion behavior of the cold-working tool steels AISI D2 and AISI O1

Abstract

The current work focuses on the effect of heat treatment on the grain size, microhardness and corrosion behavior of AISI D2 and O1 tools steels. Samples of the investigated steels were subjected to different heat treatment (quenching and tempering) regimes. The hardening temperatures for AISI D2 steel were in the range 850-1000 C with 50 C step and in the range 780-870 C with 30 C step for AISI O1 steel. The tempering temperatures were fixed for AISI D2 and O1 specimens at 550 C and 450 C, respectively, to investigate the influence of the hardening temperature only. The results show that the grain size of heat-treated steels decreased by increasing the hardening temperature and thus the microhardness number increased due to the dense grain-boundary areas in the fine structures. The corrosion behaviors of the steel specimens were assessed in 0.1-M HCl solution using a potentiostatic polarization technique. The immersed AISI D2 specimens showed better corrosion resistance than that of AISI O1 due to the presence of high alloying elements, which may help in forming a protective layer against corrosion. The corrosion rates of the coarse-grained structures were less than that of the fine-grained structures, because the finer the grains, the greater the anodic areas, which leads to higher corrosion rates. Keywords: microhardness, heat treatment