FATIGUE BEHAVIORA STUDY OF FERRITIC-MARTENSITIC CRYOGENICALLY TREATED USING 17Mn4 STEEL

Mechanical

Abstract

Based on the importance of impressive mechanical properties good ductility, reduced cost, superior formability and excellent surface finish in terms of Ferritic-martensitic steel, it has been given consideration over other high strength low alloy steels and as such, this research work has been carried out modifying the properties of 17Mn4 Ferritic-martensitic steel.
In this work, the 17Mn4 ferritic-martensitic steel specimens were made and cryogenically treated as the first step towards its modification. Fatigue, micro hardness and microstructure inspections were carried out for all treated and non-cryogenic treated 17Mn4 steel specimens. The results showed a significant increase in strength of the 17Mn4 steel compared to the commercial plain carbon steels. From the conducted experiments, the results showed that the fatigue limits for the dual and cryogenic specimens been obtained as (380MPa) and (400MPa) respectively. A considerable enhancement in the fatigue value for the cryogenic steel showed a 6.25%rise as well as the hardness value for the dual and cryogenic treated specimens increasing significantly to (186) and (198) respectively. Further investigation showed a remarkable enhancement in the hardness value to be 25% for the cryo-treated specimen. While the microstructure inspection showed that, the steel containing martensitic with less ferrite grains formed around it, the investigation proved an increment in them artensitic ratio and was seen after the cryogenic treatment was conducted.