Key Engineering Materials Vols. 373-374

Abstract: Cavitaion erosion behavior of cast iron in water and in mixed solution of 50% H2O+50% C2H6O2 with different temperature and distance between two samples have been studied by means of a ultrasonic vibrator. The mass loss of the samples at different time is recorded.The surface structure of the oxidation films on the surface of cast iron was analyzed by X-ray diffraction apparatus. The experimental results show that mass loss of the upper sample is more than that of the lower sample. The maximum of mass loss occurred when the distance between the samples is about 1.0mm. Oxidation films form on the surface of the cast iron in pure water and cannot form on the surface of cast iron in mixed solution. The XRD results show that the oxidation film mainly consists of Fe2O3 phase at 50°C, Fe3O4 phase at 80°C. The mass loss at 50°C is less than that at 80°C. Oxidation film of Fe2O3 phase has some advantages to decelerate the cavitation erosion. Mass loss of the sample of cast iron in mixed solution is less than that in pure water at 80°C. This phenomenon indicates that formation of the oxidation films plays a more important role in cavitation erosion to reduce or increase mass loss of the cast iron samples.

Abstract: A new Copper-base SHS welding material was developed to meet the demand of the welding mend about metal parts in field. The structure and properties of the welding line were studied and the results indicated that the welding was belong to fusion welding, the fusion area between the parent metal and the welding line was clear, the tensile strength of the welding line over 200MPa, the bend strength close to 600MPa and the surface hardness close to HRB130. All these indicated that this copper-base material could be used in emergency maintenance welding about metal parts.

Abstract: Nano-scale BN-C-silicone oil composite colloid was prepared in a planetary ball mill by using wet grinding techniques. Frictional experiments with GCr15 and 35CrMo as frictional pairs were then conducted under a wide range of temperature (from ambient temperature to 300°C) on a pin-plate friction and wear tester. Results show that lubricating properties of the colloid were improved significantly. In particular, the frictional coefficient of the colloid is lower than that of the pure silicone oil at both ambient temperature and high temperature. For example, at ambient temperature, the frictional coefficients ( f ) of the BN-C-silicone oil composite colloid and pure silicone oil are about 0.05 and 0.18, respectively; while at 300°C, the f value of the BN-C-silicone oil composite colloid and pure silicone oil are about 0.13 and 0.36, respectively. The characteristic of the worn surface film was also investigated by using SEM. SEM images show that on the worn surface, the concave zone is filled with some nano BN-C particles; while the rest of the particles are dispersed in the surface film. Therefore, BN-C particles may repair the worn surface, which tend to improve the boundary lubricity of the silicone oil. Finally, based on the model proposed by T.A.Stolarski, the rupture ratio of the lubricating film was discussed to address why BN-C-silicone oil composite colloid has relatively lower frictional coefficient even at high temperature.

Abstract: Two different surface treatments were adopted to form the film layers whose equivalent circuits were simulated by electrochemical impedance measurement. Discharge performance of each treated surface was studied by the electrochemical, potential step and current step in sodium chloride solution. The microstructures of treated and blank magnesium were observed by scanning electron microscopy (SEM) before and after discharge. According to the SEM observation, the discharge process of the sample treated by the nickel electroless plating had been deduced. For the electroless magnesium alloy, the experiments have proved that not only does the activity appear in the range of coating thickness, but the activity continues in the substrate metal under coating.

Abstract: In recent years, surface engineering technology has developed rapidly in China and has its unique position in government science and technology development plan. As an end user, the community of equipment maintenance has steadily focused on the latest progress of surface engineering technology and quickly introduces its achievements into equipment maintenance to improve the operational performance of weapon systems and supporting facilities. It was found during an investigation of maintenance techniques that surface engineering technology was widely used in military equipment maintenance and had made great impact for their effectiveness. Applications of surface engineering technology such as nano-surface, thermal spraying, bonding and coating, co-osmosis in maintaining and repairing airplanes, vessels, submarines, vehicles and artillery have greatly enhanced their capabilities to resist wear and tear, erosion and fatigue and dramatically improved their operational efficiency and effectiveness. Surface engineering technology has made significant contributions to maintain operational readiness of equipment and weapon systems which, in turn, has generated huge martial and economical profits.

Abstract: Nanoparticle reinforced nickel matrix composite coating, n-Al2O3/Ni, was prepared by manual brush-plating and auto brush-plating technologies. For the auto-coating, the surface was smooth and made up of large quantity spheroid grain. The observed auto-coating’s structure was dense. Compared with the auto-coating, the manual-coating’s surface was coarser, the grains that form the surface were not spheroid but anomalistic and similar to cauliflower. The structure of manual-coating was sparser than the auto-coating’s. And the test found that the auto-coating’s micro-hardness improves 8% than the manual-coating’s. Results of the friction wear testing at elevated temperature showed that the wear resistance of auto-coating decreases while the temperature goes higher. It was concluded that during the process of auto-coating, with the help of computer, the speed, pressure and flow brush liquid was stable. While during the manual process the parameters were not controlled so that the quality of the coating was influenced. The other advantage of the auto-coating was set worker free from the front line, decrease harm to worker, provide comfortable working condition, and keep the coating’s quality on a high level, can be adapted to large-scale popularization and application.

Abstract: Three kinds of coatings had been prepared on the surface of 45CrNi steel plates using laser cladded technique by adding Mo and CeO2 into the Nickel-based alloys. The wear behaviors of these three kinds of coatings in sliding against Al2O3 grinding ring were investigated by using a MM-200 Wear Tester. The results indicated that the addition of both Mo and CeO2 could improve the wear resistance of Nickel-based alloy coatings. If the original Nickel-based alloy coating was taken as the standard sample, the relative wear resistances of Mo-modified and Ce-modified coatings are 1.31 and 7.54 respectively, and the coefficients of friction appreciably decreased. SEM images of the worn surface of the coatings showed that the wear of original Nickel-based alloy coating was dominated by the mechanism of micro-cutting, and the Mo-modified coating and Ce-modified coating had a feature of fatigue wear in addition to micro-cutting. In sliding, the wearing resistance of Ce-modified coating was higher than the other two. The wear test results were closely related to the microstructures of the coatings.

Abstract: The new paint of environment-friendly was fabricated that TDE-85 and other materials incorporation into epoxy resin enhanced tenacity, strength, thermal stability, humidity resistance and corrosion resistance due to its inherent flexibility. The paint’s viscosity is less 1000mPa·s in 25°C, can spread directly. Result of the corrosion velocity test indicates the coating’s corrosion velocity in 3.5% salt-liquor less than 0.02 g/m2h. The bending and shearing strength of EW-200 buildup epoxy resin is 649MPa and 57MPa in 25°C. The strength is stable after placing -30°Cfor 12h and 65°C for 12h. The scanning electro photomicrograph shows the type of failure breaking is a tough fracture.

Abstract: In order to improve resisting performance of heat, wear and erosion as well as anti-thermal fatigue, surface build-up welding material of brake-disc for drilling rig with better performance is developed, and its wear mechanism is investigated based on friction and wear experiment at variable temperature. Morphology, constituents and phase structure of wear surface of brake disc are analyzed by employing SEM, EDAX and XRD when thermal equilibrium temperature is at 150°C and 300°C, and its tribological behaviour and wear mechanism of surface build-up welding materials are revealed. In initial stage of wear, friction temperature is lower and hard particles like AL2O3, SiO2, SiC, TiO in brake block plough the surface of brake-disc, oxide layer forms on friction surface with rise of friction temperature and its cracking and regenerating become a major way of wear, meanwhile hard grains in brake block slough off due to frequent ploughing and three-body abrasive wear occurs, and spalling of surface film is mainly caused by fatigue. In stage of high temperature wear, oxidization wear and plastic deformation of brake-disc increase greatly, brake-block starts to soften, severe adhesive wear occurs and spalling of surface film is mainly caused by adhesive tearing. Wear mechanism of brake-disc is comprehensive effects of abrasive, oxidizing and adhesive wear.

Abstract: Research on the simulation and calculation of the temperature field of friction plate in brake is one of the main references for constructing a frictional material couple. The friction heat generates on the real contact area, so the distribution of the friction heat is asymmetry and localized. In this study, the effects of real contact area on the surface temperature were investigated. Then the mathematical model of the two-dimensional unsteady temperature field of local contact area is presented. The simulation of the model for Cu-based wet friction plate indicates that the local contact has an essential influence on the surface temperature and the maximal contact temperature; the mathematic model of local contact temperature field can be used to predict the critical sliding velocity and allowable rate of energy absorbed.