In this article, the martensitic microstructure of AISI 420/DIN 1.4028/GB 0Cr13/JIS SUS420J2/3Cr13 (860℃ quenching) stainless steel will be discussed. AISI 420 is a martensitic stainless steel, which is mainly used for high-strength structural applications such as knives and scissors. By controlling the heat treat conditions, different types of martensitic microstructures were obtained in AISI 420 steel. The aim of this article is to provide a brief overview of the martensitic microstructures of the AISI 420 steel with the 860℃ quenching.
The AISI 420 steel is composed of iron, carbon and other alloying elements. The alloying elements present in the steel include Cr, Ni, Mn and Mo. The steel is heat treated to obtain a martensitic microstructure. When the steel is heated to 860℃ and quenched, it results in a mixture of ferrite and martensite. The heat treatment alters the microstructure and gives rise to different structures like lath, grain boundaries, banding and dendrites.
The laths or ledges are rod-like structures which are formed due to the recrystallization of grains. These laths are usually formed around the grain boundaries and can be seen in the macrograph of the specimen. The grain boundaries define the boundaries between the grains. The banding is formed due to the accumulation of martensite on the grain boundaries. This results in the formation of bands which exhibit distinct shades. The dendrites are tree-like structures which can be seen as a result of the rapid quenching of the steel.
The martensitic microstructures of the AISI 420 steel with the 860℃ quenching can be divided into two main categories: ferritic-martensitic microstructures and martensite grains. The ferritic-martensitic microstructures consist of laths, grain boundaries, banding, and dendrites. The martensite grains are uniform grains of martensite which are formed after heat treatment.
The mechanical properties of the AISI 420 steel depend primarily on the martensitic microstructure. The strength and hardness of the material are enhanced due to the presence of the martensite grains. The ductility and fracture toughness are improved due to the presence of the lath structure, grain boundaries, and banding.
In conclusion, the AISI 420 steel with the 860℃ quenching exhibits a martensitic microstructure composed of ferrite, martensite and other structural features such as lath, grain boundaries and banding. This microstructure enhances the strength, hardness and toughness of the material. Therefore, this steel is ideal for use in applications which require high strength and toughness.
