Research on the Mechanism of the Cracking Failure Behavior of Cast Iron Brake Drum for Heavy Trucks

Author of the article:LI Jian1 , LIU Mingfang2 , LI Shijie1 , ZHANG Weiwei3 , QIN Pengpeng1 , TAO Lei1 , LI Fushan3

Author's Workplace：1. Zhumadian CIMC Huajun Casting Co., Ltd., Zhumadian 463000, China; 2. Henan Igood Wear-resisting Technology Co., Ltd., Zhengzhou 450001, China; 3. School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China

Key Words：vehicle; heavy truck; grey cast iron; cracking failure; failure mechanism

Abstract：Braking devices play a vitally important role in the safe operation of vehicles. At present, most of the brake devices used in heavy trucks are gray cast iron brake drums. When the vehicle brakes continuously on mountain roads or ramps, initiation and growth of the crack are usually promoted on the surface of the brake drum, which will attenuate the braking effect and even cause traffic accidents. In this paper, the microstructure and microhardness of the original and failed HT250 brake drum were comprehensively investigated. The experimental results show that the microstructural size of graphite is increased in the working face of the brake drum after failure. Moreover, the crack appears in the vicinity of the interface between graphite and pearlite, and the grey phase is formed in the graphite part. In contrast, no significant change is found in the microstructure of the side face of the failure brake drum. Furthermore, the hardness of the brake drum is enhanced after failure. The cracking failure mechanism of grey cast iron brake drum is mainly that microcracks are generated between graphite and pearlite after multiple thermal cycles, which will further propagate to failure.