Fatigue Behavior Analysis of Medium Carbon Steel

Nowadays medium carbon steel is widely used in various industries for different machine applications.The most important alloying element of steel is carbon. In case of medium carbon steel the carbon composition varies form 0.25 % to 0.68 %. Mechanical properties of steels are strongly related to their microstructure. Since the microstructure of steel is greatly affected by the heat treatment method, the mechanical properties are also different for different microstructures whichare obtained after different heat treatment methods. The significance of fatigue failure of materials is a critical theme in the field of mechanical behavior of materials, since 90 % of failures are happened due to the fatigue. Rotary bending machine has been used for all fatigue testsin the present work. In this work, the fatigue behavior of medium carbon steel (rail steel, 0.62% carbon) is studied. The effect of different heat treatment methods on fatigue limit of medium carbon steel has been explored. The specimens are subjected to different heat treatment procedures like normalizing, annealing and quenching and tempering. Both normalizing and annealing is done at the temperature of 850°C for 1.5 hour whereas tempering is carried out at different temperatures (200°C, 450°C and 650°C) for different time period (1.5 hr., 2 hr. and 2.5 hr.). Fatigue limit of every specimen is identified after particular heat treatment method. Attempts have been made to find out the relationship amongst the microstructure and the fatigue limit of specimens. Experimental results show that the value of endurance limit is varying with heat treatment operations. Out of these all heat treatment process tempering at 200°C give the best result. It has been concluded that tempering at low temperature(200°C)give the better value of endurance limit or fatigue strength (574 MPa) as compared to other heat treatment method