ABSTRACT
The FE 50007 nodular cast iron is widely used in engineering applications, mainly in the automobile industry. However, in the last years the FE 50007 nodular cast iron is being replaced by the FE 50010 nodular cast iron because of its greater ductility. The ductility leads to a decrease in hardness, favoring the machining and, consequently, having a lower final cost of production. Besides the hardness, tensile mechanical properties also present a small difference between the materials. However, for engineering applications with dynamic loading the selection of the material also depends on its behavior in fatigue. Therefore, the aim of this work was to study the fatigue life of these two nodular cast irons under natural environmental conditions and after salt spray exposition. Before the fatigue tests the materials were characterized by chemical analysis, metallography, hardness and tensile tests. The fatigue tests were performed by rotating bending under natural environmental conditions and after salt spray corrosion for 48, 96, 168 and 240 hours. The FE 50007 cast iron has higher hardness and mechanical strength but less ductility than the FE 50010. These properties are related to the present phases: the FE 50007 is composed of graphite nodules, ferrite and cementite, while the FE 50010 is composed of graphite nodules and ferrite. The FE 50010 cast iron presented higher fatigue life for tensile bending equal or less than 250 MPa under natural environmental conditions. After exposure to salt spray, the FE 50010 cast iron also presented higher fatigue strength for a tensile bending of 250 MPa. The corrosion products are porous and brittle, and basically composed of iron oxides and hydroxides.
Keywords
Nodular cast iron; Rotating bending fatigue; Salt spray; Corrosion
