Study On Effects Of Heat-treatment Processes On Microstructures And Properties Of4Cr13Martensitic Stainless Steel

A certain volume fraction of retained austenite was introduced in the microstructure of martensitic steel by quenching and partitioning treatment which could increase strength and plasticity of martensitic steel. In this work, the feasibility of quenching and partitioning treatment imposed on commercial4Crl3martensitic stainless steel was mainly investigated. The effect of different Q&P heat treatment process and parameters on the microstructure evolution and mechanical properties of4Cr13martensitic stainless steel was investigated, using optical microscope (OM), scanning electron microscope(SEM) and transmission electron microscope(SEM), as well as mechanical performance test. The main results of this paper are as follows:1. When heating The annealed4Cr13steel has to austennitization,the temperature must be above1100℃in order to achieve complete austenitization, the mixed structure of lath and acicular martensite are acquired after cooling down at the same time; Below1100℃, the mixed structure of carbide particles and lath martensite are acquired because of the not fully austenitic annealed4Crl3steel.2. The fully austenitic4Cr13martensitic stainless steel is firstly quenched at different temperatures, and then partition treatment at400℃is followed. When the quenching temperature is gradually reduced, retained austenite volume fraction first increases and then decreases, which could be found peak value30%at80℃. When the time of partition treatment is constant, the increasing temperatures from350℃to400℃only make a small volume fraction of retained austenite increase, when the temperature rise to450℃, the volume fraction of retained austenite is greatly improved. The volume fraction of retained austenite increases slightly with extension of time.3. Although a centain volume fraction of retained austenite is introduced into the microstructure of the4Crl3steel by Q&P treatment, the level of strength and plasticity does not significantly increase, leading to a brittle fracture, which could be ascribed to the formation of acicula martensite in the process of quenching.4. The organizations of not fully austenitic4Cr13steel experienced Q&P treatment are retained austenite, lath martensite and carbides. Compared to reducing the volume traction of retained austenite of fully austenite, the peak temperature increase. Compared to fully austenite, the yield strength. Tensile strength, elongation of incompletability austenite has been greatly improved, but little change in toughness.