The Pearlite-Cementite Microstructure of 08 Steel After Carbonitrided and Directly Quenched
08 steel is an alloy steel composed mostly of iron, carbon and manganese. After being treated with a process known as carbonitriding, this high strength steel can be directly quenched. Like many steel alloys, the microstructure of 08 steel is altered by quenching and can have different characteristics depending on the heat treatment it is subjected to. This paper will discuss the Pearlite-Cementite microstructure of 08 steel after its carbonitrided and quenching treatment.
At the basic level, 08 steel is composed of iron and carbon with small amounts of other elements such as manganese, chromium, silicon and sulfur. After carbonitriding, the structure of the steel changes significantly. The carbon content increases, which can make the steel harder, more resilient and better resistant to wear and fatigue. The microstructure of the steel also changes significantly depending on how the steel is subsequently treated. The most common microstructure for 08 steel after carbonitrided and quenched is pearlite-cementite.
Pearlite-cementite is characterized by thin layers of ferrite interspersed with layers of harder and more brittle cementite. The ferrite provides ductility and strength, while the cementite increases the hardness and wear resistance of the alloy. The thin layers of ferrite and cementite form during rapid cooling, creating a blocky and visually distinct microstructure. Pearlite-cementite is known for providing good strength and wear resistance while also remaining toughness and ductile.
The exact microstructure of 08 steel after carbonitriding and quenching will depend on the exact parameters of the heat treatment. Slow quenching will create a finer pearlite-cementite structure with thinner layers of ferrite and cementite, while faster quenching will create thicker layers. The rate of cooling and the time spent at different temperature ranges will also affect the microstructure of the alloy, as different types of breaking down and reforming of the individual phases will occur.
In addition, the chemical composition of the steel will also greatly influence the microstructure of the alloy. Higher amounts of carbon will create more cementite and lower amounts of ferrite, while higher amounts of manganese will create finer pearlite and finer pearlite-cementite structures. In general, higher manganese content will also make the alloy stronger, while higher levels of carbon will make the alloy harder and more wear resistant.
The microstructure of 08 steel after being carbonitrided and quenched is unique and important for understanding the characteristics of the steel. Pearlite-cementite provides good wear resistance and strength and is an important part of the steel’s overall performance. The exact microstructure and characteristics of the steel will depend on the exact heat treatment and chemical composition it was subjected to and should be closely monitored and controlled.
