Dry Sliding Wear Research Of Compacted Graphite Iron With Biomimetic Coupling Non-smooth Surfaces Processed By Laser

In recent years, due to the high development of the road and aviation transportation, the department of the railway has to improve itself competition by heightening the velocity of the train transportation gradually. The world train transportation develops rapidly and the degree of high speed is more and more high. In our country the train transportation is toward the higher speed. The brake power of the train takes cubic relation with the velocity, which is to say that the velocity of the train heighten one times, the brake power of the train must elevate eight times, which gives a higher demand for the brake disc. The traditional brake disc made of grey cast iron already can't the meet the demand. The world countries come in a new high tide to investigate the materials of the brake disc. At present the primary materials of the brake disc which are using, investigating and empoldering are cast iron. The CGI bearing better thermal conductivity and higher strength naturally was discussed and investigated widely for replacing the grey cast iron. And the CGI brake disc are being used in our country now. But, But when the CGI brake disc was used for high-speed train in Japan, it was found that its wear-resistance was worse than expected [5]. The shortage of wear-resistance limits the farther and extensive application of CGI brake disc under the condition of higher speeds and heavier loads. So, it is important and urgent to investigate and enhance the wear-resistance of CGI.Organism configuration is by optimize in 20 a hundred million of almost leave nothing to be desired, we find that some of animals as dung beetle, pangolin, razor shell have non-smooth form but have good function that wearable, resist extrusion and resist crack. Accroding to character and composing of biology, we receive elicitation, and overpass analye reduce wear and wearable ect , we mastery and understand onbase which model biology coupling rules, which through bionics manufacture, we hold that material surface and surface organize configuration and variedly logical enchase of different performance organization, it come into being a new type coupling material which have a good wearable and have a good resist extrusion and resist crack.In this work, according to the principles of biomimetic coupling, the CGI specimens are processed biomimetic coupling non-smooth surface by laser with different coupling factors and investigate their wear behavior in the dry sliding process. At last, the anti-wear mechanisms of the biomimetic non-smooth units resist wear are studied.The conclusions of this work are as fellows:1. The non-smooth unit processed by laser on CGI specimens'surface consists of two typical zones, from the exterior to interior which is melting zone and heat-affect zone. The microstructures of melting zone are ledeburite + some martensite + a mass of metastable phase structure and the microstructures of heat-affect zone are martensite + retained austenite + transformative pearlite + thick graphite. The microstructure of melting zone and heat-affect zone is more compact than that of matrix so that the hardness of melting zone and heat-affect zone is much higher than that of matrix.2. West tests suggest that the wear-resistances are improved by processing designed biomimetic non-smooth units on the surface of the CGI specimens. The wear-resistances vary along with the laser processing energy density, the modes of unit embedding into the matrix and the unit distributing. With the laser processing energy density increasing, the wear-resistances improve accordingly. For the different modes of unit embedding into the matrix, the gridding has thebest wear-resistance, the dam is the second and peg is the last. The wear-resistance varies with the distributing space and angle of non-smooth unit varying. When the distributing space is 1, 2, 3mm, with the distributing space broadening, the wear-resistance of non-smooth specimen is worse accordingly. Concerning the distributing angle of non-smooth unit( 0°,45°,90°), the non-smooth units with distributing 45°shows the best wear-resistance, the 90°specimen takes the second place and the 0°specimen is the worst among the three kinds of biomimetic non-smooth specimens.3. The wear-resistances of the non-smooth specimens under the different loads and against different hardness friction pairs. With the loads increasing, the smooth and non-smooth specimens take the same rule, the wear-resistances are worse gradually. And with the difference of the hardness between the specimens and friction pairs, the wear-resistances improve accordingly. But the wear-resistances of the units against the friction pairs vary along with the laser processing energy density, the modes of unit embedding into the matrix and the unit distributing. With the laser processing energy density increasing, the hardness and the area ratio of the non-smooth units increase accordingly, as a result of that the wear behavior between the non-smooth units and the friction pairs become worse, and the difference of the wear-resistance decease accordingly. For the modes of the non-smooth units embedding into the matrix, the difference of wear-resistance is the smallest when the modes is grading, and the difference of wear-resistance is the biggest when the modes is peg. The difference of wear-resistance varies with the distributing space and angle of non-smooth unit varying. When the distributing space is 1, 2, 3mm, with the distributing space broadening, the difference of the wear-resistance decreases. Concerning the distributing angle of non-smooth unit( 0°,45°,90°), the difference of the wear-resistance doesn't vary VIvery much due to the almost equal hardness and the area ratio of the non-smooth units.4. The non-smooth units play a dominant role on improving the wear-resistance of non-smooth specimens. The main reason is the intensive particle effect generated by non-smooth units because of higher hardness and compact structure. Besides, the non-smooth unit existing on the specimen surface can reduce the contact area between the softer matrix and the friction couple, and that also can result in the better wear-resistance of non-smooth specimen. The wear process between the non-smooth specimens and the friction pair can be disported three steps: First, the friction pair contacts with raised part of the non-smooth unit close under the load before the wear. When the wear is beginning, the friction pair wears against the raised part of the non-smooth units, the raised part is so little that it can be worn out quickly, the friction pair begins to wear the matrix and non-smooth units synchronously very soon. Because of the matrix is softer and the wear-resistance is worse, the wear extent of the matrix is worse than that of non-smooth units under the same wear condition. After a while, the non-smooth units will come out from the matrix and are higher than matrix again. The non-smooth units will support the friction pair and wear against the friction pair solely. Then the non-smooth units will be worn out, the friction pair will wear against surface mixed by the non-smooth units and matrix again. The above-mention process will be repeated again and again as far as the units existing.5. The non-smooth units play a decisive role on improving the wear-resistance of the non-smooth specimens. When the non-smooth units is in the wear process(two), it can be gotten from the free-body conditions of the non-smooth units, with thearea ratio of the non-smooth units, increasing, the average load force on the single units decreases accordingly, so the friction force is little. As a result of that, the wear behavior of the non-sooth units is better, and the extent of wear-resistance is improved much more. The theory can explain the condition of the different laser processing density, different modes of the non-smooth units embedding into the matrix and the different distributing space. Concerning the distributing angle of non-smooth unit( 0°,45°,90°), the unit distributing 0°can't resist material transfer and accelerate the speed of wear; the wear-resistance is the worst among the non-smooth specimens with different distributing angle. The vertical impact force on the front edge of unit distributing 45°is smaller than that of unit distributing 90°; the speed of wear is the slowest.