Wear Behavior of Nb Alloyed Gray Cast Iron for Automotive Brake Disc Application

Gray cast iron (GCI) with a pearlitic matrix and type-A graphite remains the most widely used material in the manufacturing of brake discs. To reduce the environmental impact of disc wear during braking, alternative materials and/or compositions to the standard ones are being studied. In this study, the effect of variation in niobium content (0-0.7 wt%) on microstructure and wear behavior of samples machined from brake discs made of hypoeutectic gray cast iron was investigated. The wear behavior of GCI was examined through pin-on-disc (PoD) wear tests using low-metallic-friction material discs as the counterparts. Microstructural analyses and hardness measurements were also conducted to evaluate the effect of Nb addition on the morphology of graphite, eutectic cells, and distribution of carbides. In addition, the wear mechanisms of different samples were evaluated using scanning electron microscope analysis. The results revealed that adding 0.3% of Nb promotes the highest wear resistance of the alloys.