Combined with the relevant theories of gray cast iron casting technology, laser bionic principle, thermal fatigue and tribological principle, the effects of graphite type and carbon content on the thermal fatigue resistance and wear resistance of laser bionic gray cast iron are studied. At the same time, compared with the corresponding non bionic gray cast iron, the following conclusions are drawn:
- The initiation and propagation of thermal fatigue crack are closely related to the type of graphite. In non bionic gray cast iron, coarse C-type graphite and D-type graphite with dense dendritic gap are more likely to increase the number of thermal fatigue cracks. Moreover, for gray iron containing D-type graphite, the crack is the easiest to expand in the dendrite gap and the crack is the longest. The material with the deepest mode e fatigue crack. 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 resistance 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. According to the difference of graphite type, the hardness of bionic unit is 1.6-3.3 times that of matrix. The refinement of grain makes it have strong ability to resist crack initiation and hinder crack propagation, which is the fundamental reason for the improvement of its thermal fatigue resistance. When there is no directional graphite, the smaller the size of graphite, the better the crack arrest effect of bionic unit; Therefore, the most obvious improvement of fatigue resistance is the gray cast iron containing D-type graphite, and the effect is the worst for the gray cast iron containing coarse C-type graphite.
- The type of graphite also has a certain influence on the wear resistance of gray cast iron. The non bionic gray cast iron with D-type graphite has the worst wear resistance, but the gray cast iron with a small amount of C-type graphite has the best wear resistance. The wear resistance of gray cast iron is obviously improved by laser bionic unit, which is about 1.69-3.26 times, among which the wear resistance of bionic surface of No. D is the most obvious. However, thermal fatigue changes the structure of matrix and unit body, and the pearlite and carbide are greatly reduced, resulting in the decrease of hardness. Therefore, the wear resistance of bionic surface and non bionic surface of gray cast iron is reduced in the process of thermal fatigue.
- When controlling the graphite type of gray cast iron to type a graphite, it is found that in the process of thermal cycle, with the increase of carbon content, the oxidation resistance of gray cast iron decreases and the thickness of oxide layer increases, which promotes the initiation and propagation of cracks to a certain extent. However, the oxidation resistance of bionic unit is significantly higher than that of matrix, which improves the thermal fatigue resistance of bionic gray cast iron. In A-type graphite gray cast iron, with the increase of carbon content, the number of thermal fatigue cracks in non bionic gray cast iron increases during thermal cycle; However, the growth rate of thermal fatigue crack may have a great relationship with thermal conductivity. The crack growth rate of gray cast iron with low carbon content is faster. In bionic gray cast iron, with the increase of carbon content, the unit hardness increases and the growth rate of crack number slows down; In the later stage of thermal fatigue, the unit with high hardness is more likely to crack, so the inhibition effect of bionic unit on crack propagation decreases with the increase of carbon content.
- In gray cast iron containing type a graphite, the wear resistance after thermal fatigue mainly depends on the hardness of gray cast iron. With the increase of carbon content, the lubrication effect of graphite is enhanced, the hardness of matrix is also increased, and the wear resistance is getting better and better. However, the graphite pits and thermal fatigue cracks produced in the process of thermal cycle have an adverse impact on the wear of materials, but the impact is relatively less than that of hardness. With the increase of carbon content, the wear resistance of biomimetic surface is getting better and better due to the increase of unit hardness. Compared with non biomimetic surface, graphite pits, cracks and other defects that may aggravate wear are greatly reduced, which is conducive to improve the wear resistance of biomimetic surface.