Elevated temperature low cycle fatigue of grey cast iron used for automotive brake discs

This paper evaluates the fatigue life properties of low carbon grey cast iron (EN-GJL-250), which is widely used for automotive brake discs. Although several authors have examined mechanical and fatigue properties at room temperatures, there has been a lack of such data regarding brake discs operating temperatures. The tension, compression and low cycle fatigue properties were examined at room temperature (RT) and at brake discs’ working temperatures: 500 °C, 600 °C and 700 °C. The microstructure of the material was documented and analysed. Tensile stress–strain curves, cyclic hardening/softening curves, stress–strain hysteresis loops, and fatigue life curves were obtained for all the above-mentioned temperatures. It was concluded, that Young’s modulus is comparable with both tension and compression, but yield its strength and ultimate strength are approximately twice as great in compression than in tension. All the mechanical properties remained quite stable until 500 °C, where at 700 °C all deteriorated drastically. During fatigue testing, the samples endured at 500 °C on average at around 50% of cycles at room temperature. Similar to other materials’ properties, the cycles to failure have dropped significantly at 700 °C.