The Effects Of Biomimetic Coupling Unsmooth Units Processed By Laser On Wear Resistance Of Compacted Graphite Iron

In recent years, the light, heavy loads, high speed and low power consumption have become the inevitable development trend of the road and the rail transportation vehicles. From 1990s to now, our railway transportation system has gone through several times of great speed improvement, the highest speed has reached 350km/h, so this high speed must need especial brake disc to make the trains stopped, because the time of brake disc under the impact, the brake force and the high temperature have increased significantly, the traditional brake disc made of compacted graphite cast iron could not meet this requirement. Therefore this especial brake disc meeting the low cost and high wear resistance must be the development trend of new brake system.After millions of years of evolution,the organisms gradually adapted to the surrounding environment and shaped the were-resistance surface structure, so its could not be vulnerable to wear and tear in the long term living. The facts have proved that, through emulate this type of surface structure, preparation of biomimetic engineering surface, can significantly improve the wear resistance. Thus prepared the bionic coupling non-smooth surface which have the compacted graphite cast iron matrix and well distribution of laser melting units enhanced on it, compared to untreated compacted graphite cast iron surface, the wear resistance has greatly improved. From this experiment, we can see the excellent performance of this type of bionic non-smooth surface, and applying to improve the wear resistance of the railway brake disc, it will be the huge role in lifetime prolonging. Our research group had applied this technology in truck brake system, and the results were obvious. While because of the quickly development of china railway system, the melting units enhanced bionic non-smooth surface can gradually not meet the high dry friction wear resistance requirement, due to it's low hardness, simple enhanced layer and inferior high temperature wear resistance. So it must improve the properties of the unit to promote the wear resistance of whole bionic non-smooth surface system. This article based on the wear mechanism, the material wear resistance and the biomimetic materials analysis of theoretical results to determine the optimal wear composition and the preparation of the processing methods, then research the wear specimen with this unit.Since ancient times, ceramic materials is the better wear-resistant material, and its covalent atom structure determines the characteristics of such fine materials, its are widely used in industry in various fields, especially the harsh environment of wear-resistant conditions and high temperature environment. Prior to this, many people have been studied the laser cladding ceramic materials and received basically a good performance. Therefore, this article will be used in laser cladding technology coupled laser bionic non-smooth unit onto the prepared surface, the candidate cladding materials are TiC, WC, B4C, and Al2O3 particles, which were prepared into four types of specimens with laser cladding ceramic units, fourth specimen are tested the wear resistance experiment in different ceramic ratios and different temperatures. After test, the results showed that: 70% content of cladding ceramic materials have the best wear resistance, then gradually decreased as the reduction of contents, so it obvious that the 10% content have the lowest wear resistance. Otherwise, the TiC specimens have the best wear resistance than other three ceramic materials, the Al2O3 specimens have the lowest one; We chose the 70% content as the optimal content to test the temperature sensitivity, which showed that the cladding TiC specimens have the best temperature resistance, no matter what temperatures, 200, 400 or 600℃,the wear mass loss is the lowest, then the cladding WC specimens and B4C, the last and the worst one is the cladding Al2O3 specimens. TiC cladding has the best one as a result of the TiC particles melt into the unit are not broken down and combined with the matrix well; cladding WC unit has the second one as a result of the WC particles molten into surrounding iron at high temperature easily, and then formed a M6C-type carbides, which makes cladding WC unit has lower wear resistance than TiC cladding unit, but also has good wear resistance under different temperature performance; cladding B4C unit has the third one as a result of B4C particles react with the substrate and generate FeB phase, reducing its original features, making the lower wear property than the TiC cladding; cladding Al2O3 unit, as a result of such a light weight of ceramic particles, and the small contact angle with the substrate, and so on for their own material reason, so its can not form good performance units, and the worst wear resistance. In particular, TiC and WC unit with low sensitivity to temperature.In addition, the depth of laser cladding enhanced complex unit were prepared by pre-powdered in deep groove method, the candidate enhanced materials were selected on the basis of the result of superficial cladding which has reported above. Through the fixed slot size, while optimizing the laser parameters by orthogonal methods to get unit to reduce the impact of factors, at the same time to gain the most well-depth of laser cladding enhanced complex unit. This unit has a certain depth distribution of the reinforcing materials, so that the enhanced depth has three times more than the superficial cladding method, greatly improved the laser coupling bionic non-smooth surface of wear-resistant properties.This article mainly studied the unit's microstructure distribution, as well as their advantages and disadvantages of the wear resistance through cladding of different contents of WC ceramic particles into the unit. At the same time, through researching the excellent wear resistance and good economic considerations of high chromium cast iron, the depth of laser Cr allying in situ unit were prepared to study the microstructure distribution and wear resistance. Obtained: the depth of in situ laser cladding ceramic WC unit with a larger microstructure gradient, and have formed a complex tungsten compounds such as iron with carbon, the main phase are M6C carbide and WC particles, both phases have the supporting role in the unit body wear, the unit has a high hardness, the upper part of the unit microstructure is the well distribution network of M6C carbide, while the lower part are the shape of the main multilateral M6C phase and a mixture of WC microstructure. It can be inferred that, with the wear and tear, the unit will be getting better and better of wear resistance. Through the room temperature wear test also proved that the depth of in situ cladding unit with better wear performance; and laser depth in situ Cr alloying unit are mainly the solid solution strengthening of the austenite and M7C3-type carbides, the types of microstructure distributed more uniformity. However, compared to high-chromium cast iron, the unit contains less M7C3 carbide, so little to improve the hardness, thus wear resistance improving is limited, but because of solid solution strengthening and dispersion strengthening the role of the grain boundary, the unit still has better wear resistance than Laser Melting specimens.Through the study of this article, this new type of biomimetic coupling non-smooth surface processed by laser was applied onto the brake disc with a smaller preparation costs, and can meet the demanding requirements of brake disc of modern trains, this brake disc also have excellent wear resistance in the service time and a certain thickness, so it can perform the adequate wear-resistant, eventually increasing the service life of brake disc and the use efficiency, save money and improve the efficiency of railway operations.