Microstructural Modifications in AISI 1080 Eutectoid Steel Under Combined Cyclic Heat Treatment

In this research work annealed AISI 1080 steel bars are subjected to a typical combined cyclic heat treatment involving two cycles. The first cycle consist of inserting the specimen in an electric resistance furnace at a temperature of 775 °C (in fully austenitic region) and holding for a short duration (6 min), followed by forced air cooling to the room temperature. In second cycle holding temperature and time being same, the specimen is subjected to oil quenching. Such a typical combined thermal cycling results in the evolution of a novel microstructure that comprises of submicroscopic cementite spheroids and fine microscopic cementite clusters in a matrix of martensite. Accordingly, very high hardness (894 HV) is achieved which envisaged a new heat treatment route of the development of plain carbon tool steel.