Comparison of Microstructure and Mechanical Properties of Mo40 Steel in Ferrite-Martensite dual phase and quenched tempered condition

In this research, has been compared fatigue behavior of Mo 40 steel in ferrite-martensite dual phase condition and quenched-tempered microstructure. The ferrite-martensite dual phase samples were prepared from intercritical annealing heat treatment process for 40 minute at ( α + γ ) dual phase region. The quenched martensite samples after heating at 860 ° C and quenched in water, were tempering heat treatment at 600 ° C for 3 0 minute. The Hardness, tensile and fatigue tests have been supplemented with optical and electron microscopies. The result shown that hardness of ferrite-martensite dual phase is more than quenched tempered sample. Also , tensile strength of ferrite martensite dual phase samples is lower than quenched-tempered sample, while the fatigue strength of samples is more than quenched-tempered sample. These results are rationalized to strengthening un tempered martensite phase in ferrite martensite dual phase sample compared to tempered martensite in quenched tempered sample.