With the continuous increasing of wagon load and running speed, all parts of freight cars have been received more loading weight. The coupler is the key part for linking locomotive and rolling stock, but coupler body has been detected failure phenomenon such as crack with the abominable running condition, which has been serious incipient fault of railway transport. Heavy load and increasing speed is the trend in our country’s wagon development, so it is significant to develop high comprehensive properties reserved material for coupler.Failure analysis has been done in current couplers with cracks in coupler yoke key; aimed at high comprehensive properties reserved material, The chemical constitution has been adjusted and smelting method has been improved for the new steel, it’s heat-treatment processing parameters has also been optimized, it’s repeated tension and compression behavior, low-temperature impact behavior and frictional behavior are also has been tested.The results showed that the surface cracks of coupler yoke start from some spots of (?)ction arc surface, and expanding forwards along radial direction in a brittle fracture way. When arrivd the intermediate zone between basal body and hardening zone, the crack turned to axial and circumferential direction and expanding in fatigue way. After chemical constitution adjusting and smelting method improvement, the mechanical property of new ZG29MnMoNi-E grade steel meets the standard of TB/T2942-1999 and AAR. M 211 , and surpasses the average level of current material for coupler used in two most famous railway factory. The fatigue strength of new steel is 342MPa, better than current steel by 9.26%; after wearing for 1 hour matched with 40Cr, the wear loss of new steel is 0.0115g, it is lower than current steel by 40%; low temperature impact work at -40℃of new steel concentrates in 60-80J, it is 2-3times of current steel. So new grade E steel have great engineering reference value to the replacement of key parts of heavy load train and broad prospects.

With the continuing development of high-speed electrified railway, the contact wire demands the copper alloy to have high electrical conductivity and mechanical properties, but also have excellent wear-resisting and high anti-softened properties. Al₂O₃/Cu composite has recently made their debut as potentially viable and attractive engineering materials for industrial applications that require high strength, high thermal- and electrical-conductivity, and high resistance to softening at elevated temperatures. Internal oxidation has been regarded as the most suitable method for Al₂O₃/Cu composite. This paper researches Al₂O₃/Cu composite with different A12O3-content prepared by internal oxidation. Based on the performance requirements by the high-speed railway on the contact wire material and strengthening mechanism of Al₂O₃/Cu composite, three materials containing 0.24wt%Al₂O₃, 0.40wt%Al₂O₃ and 0.60wt%Al₂O₃ separately prepared by internal oxidation were designed, and the electrical conductivity, hardness and tensile strength properties of the composite were tested. The tribological properties with and without current of Al₂O₃/Cu composite were investigated on self-made electrical sliding-wear tester. The influence of current, velocity and load on the wear rate of the composite were studyed by compareing with Cu-0.36Cr-0.06Zr. The morphologies of friction surface and vertical section of the composite were also examined with scanning electron microscopy （SEM） and energy dispersive X-ray spectrum （EDS）, and its abrasion mechanisms were discussed. The research is to explore the engineering applications on electric sliding field for providing theoretical basis about Al₂O₃/Cu composite.The following points are considered as the main conclusions:The Al₂O₃/Cu composites containing 0.24wt%Al₂O₃, 0.40wt%Al₂O₃ and 0.60wt%Al₂O₃ separately prepared by internal oxidation can obtain good integrated properties to meet the performance requirements of the contact wire, and the electrical conductivity reach 93%IACS, 89%IACS and 85%IACS, the tensile strength are 530MPa, 585MPa and 607MPa, and the micro-hardness are 152HV, 165HV and 178HV.The wear resistance of Al₂O₃/Cu composite is superior to that of Cu-0.36Cr-0.06Zr alloy under the same conditions, especially, 0.40Al₂O₃/Cu and 0.60Al₂O₃/Cu. The wear rate of all the materials under investigation increases with the increasing of current and sliding time under certain load. And the influence of current on wear rate is not obvious for 0.40Al₂O₃/Cu and 0.60Al₂O₃/Cu, while it is very notable for 0.24Al₂O₃/Cu and Cu-0.36Cr-0.06Zr. Moreover, the growth rate of wear rate of both 0.24Al₂O₃/Cu and Cu-0.36Cr-0.06Zr are higher than that of 0.40Al₂O₃/Cu and 0.60Al₂O₃/Cu. Besides, the service life of wear of 0.40Al₂O₃/Cu and 0.60Al₂O₃/Cu will appear in more and more superiority than the Cu-0.36Cr-0.06Zr alloy with the extending time during the electrical sliding wear processes. The wear rate of Al₂O₃/Cu composite decreases with the increasing of Al₂O₃-content under the same testing. Compared with 0.24Al₂O₃/Cu, 0.40Al₂O₃/Cu and 0.60Al₂O₃/Cu have higher wear resistance under the same conditions.The wear mechanism of Al₂O₃/Cu composite were adhesive wear and abrasive wear without current, while adhesive wear, abrasive wear, oxidation and electrical erosion would be the dominate mechanism under currents. The trend of adhesive wear would be serious with the increasing of current. The adhesions of Al₂O₃/Cu composite come from the copper-based powder metallurgy strip. By comparison, for Cu-0.36Cr-0.06Zr, the wear mechanism were the adhesive wear, abrasive wear and oxidation wear without current, while changed into adhesive wear, abrasive wear, oxidation and electrical erosion with current. Moreover, oxidation and electrical erosion were become more and more severe with the increasing of current.Based on the experimental study, Al₂O₃/Cu composite prepared by internal oxidation meets the performance requirements of the contact wire, and the Al₂O₃-content of Al₂O₃/Cu composite contact wire is 0.40～0.60wt%.

According to this research, Fe-based amorphous alloy coating （containing Cr, Mo, Ni, P, B, Si） was deposited by air plasma spraying（APS） technique. The properties of the coating was investigated by means of Microhardness Tester, Optical Metallographic Microscopy（OM）, X-ray Diffraction（XRD）, Scanning Electron Microscopr（SEM）,Differential Scanning Calorimentry（DSC）, Corrosion and Wear resistance experiments.The correlations between spraying parameters and the performance of as-sprayed coating oriented in microhardness and porosity was studied. Through orthogonal experimental design, the optimized parameters were obtained. When the Ar flow rate was 40 L/min, current was 550 A, arc voltage was 60 V and stand-off distance was 100 mm, the porosity of coating was as low as 0.89%, the microhardness was as high as 831.9 HV_0.1. A dense, homogeneous and lamellur coating with high fraction of amorphous phase was obtained, which was composed of deformed strip shaped particles, un-melted particles, some porosity and cracks. It was found that the substrate and the coating was mainly mechanical bonding.The DSC showed that the crystallization temperature of coating began at 552℃and ended at 620℃. According to XRD patterns, the heat treated coatings with the temperatures lower than 550℃had an amorphous structure. When the annealing temperature was among 550℃and 800℃,α-Fe phase began to crystallize, then Ni₃P,Cr_1.2Ni_0.8P. With the extension of annealing temperature to 800℃, the fully crystallized sample consisted of FeNi₂P、Fe₃B_0.8P_0.18 and Fe-Ni solid solution with grain size growed was obtained. Through statistical analysis, the microhardness of coating under different annealing condition presented both normal and logarithmic distribution. The microhardness of coating increased with the raise of annealing temperature and the extension of duration time below annealing temperature of 500℃, and fluctuated above annealing temperature of 550℃.It was found through electrochemical and immersion test that the amorphous coating underwent the course of active dissolution-passivation-repassivation in 1N H₂SO₄, 10% NaOH and3.5% NaCl. The corrosion current density i_corr and passivation current density i_p of coatings in the above three electrolyte were both lower than the corresponding stainless steel substrates, and the corrosion rate reduced sharply after polishing treatment. The amorphous coating exhibited the best corrosion resistant capacity in NaOH solution, the worst in HCl solution. The heat treatment didn’t have much effect on the electrochemical parameters of coating. The microhardness of coating decreased with the increase of test load, exhibited phenomena of indentation size effect. The fracture toughness of coating was superior to bulk amorphous alloy with average K_IC estimated at 2.7084 MPa·m^1/2. The coating also had better wear resistance.All the analysis indicated that by APS technique a amorphous coating alloy with high microhardness, density, good corrosion and wear resistance based on optimized parameters can be achieved

Surface engineering technology is the important part of the advanced manufacture technology, and which afford technology support innovation of the advanced manufacture technology. Surface engineering technology is particular advantage on surface protected, surface repair, changing the performance of surface etc. High Velocity Arc spraying is one of surface engineering technology, with the development of thermal spraying technique and materials, High Velocity Arc spraying coating extend the range of material applications, enhance the work life of parts, saving the sources.Aimed at the actual works in the curing cycle bed boiler erosion of the surface wear resistance requirements, researching the technique, material and supporting technology of High Velocity Arc spray. Used Q235 steel as basic material, select the HDS-88A wear-resistance high-wire material, and its basis: ceramic composite metal borides, Ni, Cr, Al, thulium. Adopt the High Velocity Arc spraying the coating on the Q235 steel.Make sure the current、voltage and distance of the High Velocity Arc spraying under the method of orthogonal design theory, and the current、voltage and distance impact of wear, hardness and tiny-hole of coating.MM200 respectively use friction and wear test machine and MLS-225 wet-sand rubber wear tester of composite ceramic coating metal borides in the dry friction conditions and erosion wear under conditions of the experiments wear, the result indicate that the coating’s wear-resistance under the dry friction much better than under the erosion friction.The hardness of coating also be tested under Huayin Vickers hardness-HV-1000, and the tiny-hole of coating be tested under DT200 image analysis software and metallographic microscope XJ100.The use of mathematical statistics, through orthogonal design to determine the appropriate parameters, the establishment of quadratic regression methods, and established the Spraying current, voltage, and distance and wear between the mathematical model and identify the best process parameters. The research of experiments indicate that High Velocity Arc spraying metal borides composite ceramic coating quality is good and has good wear resistance, the use of mathematical statistics.

Hot Forging Die is an important processing equipment in Forging industry. It will bear cyclical thermal load and mechanical load during the hot forging process. The service life of hot forging die is short because of its adverse working environment. So, it is important to increase the die service life. In this paper, the final forging process of wheel is simulated, using the software DEF0RM-2D . In order to reveal the working state of hot forging die and find an effective method to prolong the die service life, some key problem affecting the die service life were studied . The contents are as follows :1、The study of Temperature distribution and Tempering Behavior of hot forging die . Temperature is the main factor affecting the die’s tempering behavior .The phenomenon of thermal soften will appear when the temperature of die increased ,and it will cause the hardness decrease. The tempering coefficient P determine the hardness . The violent wear lead to die scrap if the tempering coefficient P decrease to some value . The influence of the effective tempering temperature and the effective tempering time on die service life was obtained . Reducing the contact time between workpiece and dies is an efficient approach to improvement of hot forging die service life.2、The analysis of hot forging die wear. The wear of hot forging die was obtained , and the violent wear appear at the mould cavity comer . The wear was determined by interface pressure, sliding velocity, hardness etc . The effective method about improving service life is enhancing the hardness of die . The service life can be predicted by the wear depth. The adequate cooling of hot forging die after each process can improve the service life .3、The preform optimization . The preform shape of workpiece confine the metal flow and control the deformation and affect the microstructure performance . In this paper , the preform optimization is simulated , using the software DEF0RM-2D . The optimization of preform shape can get through reverse operation based on FEM . The optimization preform shape checked by forward operation and the results show that the variation of effective strain trend to uniform , the forming force and the effective stress are decreased.4、The study of multilayer metal die . hi this paper multilayer metal coating was made based on the thought of multilayer metal die design .The Xrd analysis about cladding was detected. The result shows that the cladding can improve the hardness of die .The model of multilayer metal die was built successfully and the analysis was obtained .The comparison of physical field between homogeneous hot forging die and multilayer metal hot forging die was obtained. The temperature peak and the effective stress was decreased. Multilayer metal hot forging die was proved feasible through theoretically and practically .All research provide a reference to the multilayer metal and a basis for the applications of FGM.

Hot Forging Die is an important processing equipment in Forging industry. It will bear cyclical thermal load and mechanical load during the hot forging process. The service life of hot forging die is short because of its adverse working environment. So, it is important to increase the die service life. In this paper, the final forging process of wheel is simulated, using the software DEF0RM-2D . In order to reveal the working state of hot forging die and find an effective method to prolong the die service life, some key problem affecting the die service life were studied . The contents are as follows :1、The study of Temperature distribution and Tempering Behavior of hot forging die . Temperature is the main factor affecting the die’s tempering behavior .The phenomenon of thermal soften will appear when the temperature of die increased ,and it will cause the hardness decrease. The tempering coefficient P determine the hardness . The violent wear lead to die scrap if the tempering coefficient P decrease to some value . The influence of the effective tempering temperature and the effective tempering time on die service life was obtained . Reducing the contact time between workpiece and dies is an efficient approach to improvement of hot forging die service life.2、The analysis of hot forging die wear. The wear of hot forging die was obtained , and the violent wear appear at the mould cavity comer . The wear was determined by interface pressure, sliding velocity, hardness etc . The effective method about improving service life is enhancing the hardness of die . The service life can be predicted by the wear depth. The adequate cooling of hot forging die after each process can improve the service life .3、The preform optimization . The preform shape of workpiece confine the metal flow and control the deformation and affect the microstructure performance . In this paper , the preform optimization is simulated , using the software DEF0RM-2D . The optimization of preform shape can get through reverse operation based on FEM . The optimization preform shape checked by forward operation and the results show that the variation of effective strain trend to uniform , the forming force and the effective stress are decreased.4、The study of multilayer metal die . hi this paper multilayer metal coating was made based on the thought of multilayer metal die design .The Xrd analysis about cladding was detected. The result shows that the cladding can improve the hardness of die .The model of multilayer metal die was built successfully and the analysis was obtained .The comparison of physical field between homogeneous hot forging die and multilayer metal hot forging die was obtained. The temperature peak and the effective stress was decreased. Multilayer metal hot forging die was proved feasible through theoretically and practically .All research provide a reference to the multilayer metal and a basis for the applications of FGM.

The wear of machine parts exist universally, they cause huge energy loss of energy and material. Wear reduces mechanical device’s performance, the reliability as well as the service life seriously. Martensitic stainless steel coating arc sprayed can effectively repair worn parts, strengthen the surface performance of material, enhances mechanical device’s service life. Moreover, the technology of arc spraying martensitic stainless steel is also used in the many kinds of rapid tool manufactures.Four kinds of different carbon amount martensitic stainless steel, 1Cr13, 3Cr13, 4Cr13 and 7Cr13, were employed in this experiment. They were sprayed by using different arc spraying technological parameter to obtain the corresponding coating separately. Through the tests of the coating samples with a wet sand oak rubber wear testing and a sand blasting installation separately, the influence of arc spraying technological parameter on coating’s wear resistance was studied. Using the method of tin soldering, silver brazing and TIG welding, the weldability of 4Cr13 stainless steel coatings were studied, and the suitable technology for welding of the coatings were looked for. By means of SEM, the microarea power spectrum analysis as well as the XRD analysis, the microstructure of spraying martensitic stainless steel coating and welded joints’ microstructure of coating were investigated and analyzed in this article. And, the bonding strength between coating and substrate, bonding strength of welded joints, the tensile strength of coating itself as well as the Vickers hardness of coating were measured.The results showed that with the increasing of the spraying current, the wear resistance of the coatings was getting higher, the increasing of the spraying voltage could decrease the wear resistance of the coatings and the increasing of the spraying distance could also decrease the wear resistance. It also revealed that with the increase of the spraying distance, the Vickers hardness of the coatings descended and that the more carbon content in the wire, the better wear resistance the coatings had with the same spraying parameter. Polished coating surface could significantly improve the brazing process performance. Silver brazing could well joint the carbon steel substrate and the stainless steel coating polished. Spraying a layer of carbon coating on the coating surface of martensitic stainless steel could be benefit to the tin soldering’s reliability of coating. The tensile strengths of the joints were more than those among the layers of the coatings. The bonding strength between 4Cr13 coatings and substrate were equally 26.9MPa, the tensile strength of coatings were 129.95MPa equally. With the same spraying technological parameter, the higher the carbon amount of wire, the higher the hardness of coating. The average hardness of 7Cr13, 3Cr13 and 1Cr13 coating was separately about 439.88HV, 379.01HV, 281.08HV.

The novel（Al₃Zr+Si）_p/Al matrix composites are prepared by in-situ melt reaction from Al-2OSi and K₂ZrF₆.The solidification microstructure,in-situ particulate features of the prepared composites have been investigated by using Optical Microscope（OM）,Scanning Electron Microscope（SEM）,Electron Probe Microanalyzer（EPMA）,X-ray Diffractometer（XRD） and other modem equipments. Mechanical properties and wear property have also been tested.The nature and mechanism of these characteristics have been analyzed.The optimum parameters of the formed composites in the Al-2OSi-K₂ZrF₆ system are that the initial reaction temperature is about 800℃,the reaction time is 15 minutes,the mass fraction of the adding reactant is 15%of the melt aluminum.The XRD and SEM analyses indicate that the synthesized practices are Si and Al₃Zr. These practices are free and well-distributed in the aluminum matrix.The average size of the primary silicon is about 20μm,while that of Al₃Zr reinforcement particulates is about 5μm.After multiple modified by P-Cu and RE,the size of primary silicium are more refined.Results of mechanical property testing show that the tensile strength and hardness of（Al₃Zr+Si）p/Al composites are higher than that of its matrix alloy, respectively,and increased with the increase of the volume fraction,but the elongation decreased.With 5.5vol%of in-situ particulates,the values forσb and HB have been increased by 41.6%and 39.7%of those of Al-2OSi,to 194MPa and 95, respectively.The tensile fracture morphology and mechanism of（Al₃Zr+Si）p/Al composites are observed and analysed.Results indicate that the fracture mechanism is brittle fracture and the strengthening mechanism of in-situ Al₃Zr particles reinforced aluminum matrix composites include reinforcement phase strengthening,solid solution strengthening and finer crystal strengthening.Dry sliding wear tests at room temperature show that the wear resistance of the composites is superior to that of its matrix alloy.The wear mechanisms of the composites determined by SEM microstructures of the wear surface and subsurface show that the wear mechanisms of the composites is adherence wear and abrasion wear.Under the same load,the wear mechanism transforms from adherence wear and abrasion wear to abrasion wear with the increase of the volume fraction of the reinforced particles.Under the same volume fraction of the reinforced particles,the wear mechanism transforms from abrasion wear to adherence wear and abrasion wear with the increase of the load.

Roll is the important part of mill, which is contact directly with the steel plate and make it generate plastic deformation. In rolling, roll is easy to fail, The main modes of failure are wear, crack in the surface and flake. Wear and flake damage the original shape of rolls, which affect the plate shape and the plate crown directly, it is very hard to control the product quality, roller failure has greatly increased the consumption. it is very important for theory value and practical significance to study roller f failure, which can reduce the cost of the production, the consumption of the roller and improve quality of plate.Firstly, the paper analyzed the failure mechanism and reasons of cold roller, research the commonly rule of roller failure, and then analyzed the failure reasons deeply in the way of mechanics. At the same time, established the crack initiation life prediction mode of work roller.Secondary, considering elastic deformation of roller and elastic-plastic deformation of the plate, based on the finite element software MARC, set up a three-dimensional emulational model of the four-high rolling mill and HCW rolling mill. The model considered the rolls and plate as a system , has resolved the coupling problem of the plate deformation and the rollers deformation.Finally, calculated the stress field using finite element. Analyzed the effect of surface stress to wear and fatigue failure of work roller, then through compared the data calculated by finite element with calculated by analytic method, verified the accuracy of finite element model. Study the influencing rule of strip width, reduction ratio, bending force, work roll shift and both bending force and work roll shift to rolling pressure, the pressure between rollers and roller failure, and predicted the fatigue life of work roll in different rolling parameters, brough forward measures of reducing roller failure.

Zinc-Aluminium based alloys have excellent mechanical and tribological properties,and can partially substitute tin bronze to prepare some wear-resistant and anti-friction components.Adding silicon into the zinc-aluminium based alloys can further improve their wear resistance.In this work,the dry sliding wear properties of ZA27-0.2Si alloy were investigated.Simultaneously,the wear properties wear compared with those of ZCuSn5Pb5Zn5 bronze under different loads and sliding speeds.The aim was to examine the substituting range for the bronze and provide some supports for practice.In addition,taking a machine tool bush as an example,the casting techniques of the ZA27-0.2Si were studied.The wear tests were performed on a pin-on-disk tester.The sliding speed ranged from 0.1 m/s to 0.7m/s and the loads ranged from lkg to 9kg,the testing time was 20min.The results indicated that the ZA27-0.2Si alloy had good wear resistance under low speed and high load which the ZCuSn5Pb5Zn5 alloy was suitable for applying under low speed and low load,which implied that the former alloy had a wider application range than the latter one.As the load increased,the wear mechanism of the zinc alloy changed in turn of adhesion and micro-machinging to abrasive wear accompanied by adhesion,plastic deformation induced wear and delamination wear.When the sliding speed increased,machining wear was enhanced and the smear wear finally occurred due to the temperature rise of the contacting surface.The microstructures of the wear surfuce and sub-surface layer determined the wear properties.The formation of transfer layer improved the wear properties.The wear mechanism of tin bronze was abrasive wear and sevre deformation occurred under high loads due to its low shear strength.The application of high temperature steel mould and cooling by water was benefical for directional solidification,so the bottom shrinkage could be overcome and inclusions and gas pores were easy floated.Suitable mould temperature and pouring temperature were the key factors for preparing casting without defects.In this work,the suitable casting parameters were the mould temperature 350℃of and pouring temperature of 580℃The application of high pouring temperature was necessary for preparing components without defects during sand mould casting.This could prolong the solidification time and was beneficial for floating of inclusions and avoid the formation of inclusions in the castings.The suitable sand mould casting technique was the application of bottom pouring.the ratio of sprue-runner-gate inner of 1:1.5:1.3,the pouring temperature 580℃