The wear caused by the severe friction of the brake drum in the braking process and the fatigue cracking caused by the alternating phenomenon of cold and heat often lead to the failure of parts. Due to the differences of casting process and chemical composition, gray cast iron brake drum often forms different types of graphite. Graphite, as the soft phase in gray cast iron, has a special position in the influence on the properties of gray cast iron. Therefore, it is necessary to study the effects of different graphite types on the thermal fatigue and wear properties of gray cast iron. Laser Biomimetic Coupling treatment forms a special structure similar to the “soft and hard” on the surface of the material, which is of great help to improve the fatigue resistance and wear resistance of the material in theory. In practice, the material of gray cast iron also has a certain impact on the bionic unit, so it is necessary to study the bionic morphology of different gray cast iron. In this chapter, the thermal fatigue and wear properties of non bionic surface and bionic surface of gray cast iron containing five different graphite types are studied to determine the effect of graphite types on fatigue cracking and wear resistance of materials. At the same time, the influence of graphite type on Laser Biomimetic unit and the role of unit in crack arrest and wear resistance are studied.
The thermal fatigue and wear properties of non bionic and laser bionic gray cast iron containing different graphite types are compared, and the influence of graphite types on thermal fatigue and wear resistance is analyzed. The following conclusions are drawn:
The initiation and propagation of thermal fatigue crack are closely related to the type of graphite. Among them, coarse C-type graphite and D-type graphite with dense dendritic gap are more likely to increase the number of thermal fatigue cracks. In the materials containing D-type graphite, the crack is the easiest to expand between dendrites and the crack is the longest. The material containing E-type graphite has the deepest crack in the later stage of thermal fatigue. The thermal fatigue crack initiation and propagation threshold of gray cast iron containing type A and type B graphite is high and its performance is good. The thermal fatigue performance of type a graphite gray cast iron is the best.
The thermal fatigue resistance of gray cast iron surface with laser bionic structure is obviously better than that of non bionic gray cast iron surface. The fundamental reason for the improvement of thermal fatigue performance of bionic unit is that it has strong anti crack initiation ability and hinders crack propagation. When there is no directional graphite, the smaller the size of graphite, the better the crack arrest effect of bionic unit. Among them, the most obvious improvement of fatigue resistance is the gray cast iron containing D-type graphite, while the gray cast iron containing coarse C-type graphite has the worst effect.
Through the research on the wear resistance of gray cast iron containing different graphite types, we find that the wear resistance of gray cast iron containing C-type graphite is the best, while the bionic surface wear resistance of gray cast iron containing D-type graphite is the most obvious. Thermal cycling is equivalent to continuous heat treatment, which changes the structure of the material, reduces the content of pearlite and increases the wear performance. Although the wear resistance of bionic surface decreases after thermal cycling, it is better than that of non bionic surface after thermal fatigue.