Applied Mechanics and Materials Vols. 217-219

Abstract: A novel hexanedioyl thiourea chelating resin(HTR) was synthesized through interfacial polymerization of hexanedioyl diisothiocyanate and polyethylene polyamine. Its structure was confirmed by FT-IR. The adsorption properties of HTR for Ag(I) were investigated by batch operation . The results show that the adsorption equilibrium of HTR for Ag(I) is achieved after 12 hour at 20°C, the equilibrium adsorption capacity is 4.56mmol/g and increases as the temperature or pH rises, the adsorption process accords with G. E. Boyd equation and Langmuir adsorption isotherm as well, and the silver-loaded resins can be quantitatively eluted by a solution containing 6% thiourea in 1mol/L HNO3.

Abstract: Double-coating of hot-dip aluminizing is a process of protecting steel from being oxidized. The process is featured that the component is firstly hot-dip galvanized and finally hot-dipped with aluminum. The comparison of interface morphology was conducted for single hot-dip aluminizing and double-coating of hot-dip aluminizing on Q235 steel sheets. The metallographies of the cross-sections were observed and analyzed with SEM, XRD and EDS, respectively for the specimens prepared by the two processes. The experimental results indicate that there is no Zn-Fe alloy layer formed in the double-coating, and both single and double coating have similar phase compositions. However, the interface between the alloy layer and the steel matrix is smoother for the double-coating than that for single-coating.

Abstract: Aluminum alloys have good properties such as high strength-to-weight ratio, corrosion resistance and relatively low cost. Nowadays they are primarily used as wrought and cast in many industries such as automotive, aviation and aerospace because of these properties. Aluminum alloys are classified into two categories as non-heat-treatable and heat-treatable. The mechanical properties of the heat-treatable alloys are improved by solution heat treatment and controlled ageing. While mechanical properties of some heat-treatable alloys, especially 2XXX series, become stable with natural ageing at room temperature within a few days, some of them are unstable and exhibit significant changes in properties even after many years. Heat treatment process of AA 2024 is very sensible and critical and therefore should be carefully performed. In this research, effects of the solution temperature, soaking time, heating rate and quenching delay condition of AA 2024 on the mechanical properties were investigated.

Abstract: The process of ion nitriding and multi-arc ion plating compound preparation Ti_0.33Al_0.67N membrane layer, it is the hot research spot of coating technology at present. Under the premise of this process, how to get better performance of thin-film coatings is the focus of research. Based on thin film deposition process parameters by orthogonal experimental design, an appropriate test process has been developed. Micro-hardness instrument is applied to test the surface hardness of the film and the droplet, By using scratch method to test the adhesion of coatings, analyzing the effect of a negative bias of substrate and nitrogen partial pressure, alloy target current process parameters on surface morphology of films, film thickness, adhesion and hardness has concluded the optimal process parameters. The results show, the thickness of the (Ti, Al) N super hard film that deposited by multi-arc ion plating technology is about 2.7 microns, through the deposition process optimization can achieve a high level of hardness (HV > 2600) and strong adhesion strength (>35 N).

Abstract: 40Cr steel substrate was coated with Ti_0.33Al_0.67N films by Multi-arc ion technology. Analyses of substrate negative bias voltage on morphology thickness of the film, bonding strength and micro hardness and other properties. The substrate negative bias parameter designs within the scope of the existence of an optimal value, in order to get the optimal performance of the film.

Abstract: Micro wire electrical discharge machining (MWEDM) and flat grinding were used to manufacture test specimens of W18Cr4V. Electrochemical impedance spectroscopy and potentiodynamic polarization curves were made to test the corrosion resistance of specimens’ surface with micro cell and electrochemical workstation. Besides, the surface micro-topography after corrosion had been observed with inverted metallographic microscope. The results show that MWEDM surface is better than flat grinding surface in the corrosion resistance. The best Anticorrosive discharge energy of W18Cr4V is 1.25J.

Abstract: The technology of metal surface strengthening with plasma arc has quite different characteristics of High frequency quenching. The results similar to that of the laser beam. The properties make it possible that develop a plasma arc heating robot as a portable device for the case surface strengthening of steels. The characters of the plasma are analyzed at first, then the plasma arc as Guess distribution circular heat source is studied to create the surface strengthening temperature field and heating process. The surface strengthening technology and the hardware design of the plasma arc surface- strengthening robot is given.

Abstract: By argon arc cladding technology, a Fe-based alloy coating was prepared on the surface of Q235 steel. The microstructure of the cladding coating was investigated by optical microscope (OM) and scanning electron microscope(SEM). The microhardness and wear resistance performance of the coating were tested by microhardness tester and friction-wear tester. The results show that the alloy coating with martensite, alloy solid solution and (Cr, Fe) 7C3/Fe3C/ Fe2B compounds is prepared on the surface of Q235 steel, the microhardness of the coating reaches as high as 600 HV and the wear resistance of the coating is about 8 times higher than that of Q235 steel substrate. When deposited a wear-resistant layer on the surface of mild steel , the high plasticity and ductility are preserved as well as the hardness and wear resistance of the cladding layer are improved greatly.

Abstract: CaO-MgO-Al₂O₃-SiO₂ glass-ceramics were produced by using waste casting sands as a main raw material. Friction and wear tests for the glass-ceramics were conducted with M-200 wear tester against GCr15 steel wheel. The worn morphologies, wear mechanisms and compositions of the glass-ceramics were observed and analyzed with scanning electron microscope (SEM) and energy diffraction spectrum (EDS). The results show that under the dry friction sliding the glass-ceramics present high wear rate and friction coefficient, with wear mechanisms are dominantly brittle spalling and some with adhesive wear. By an addition of 10% pure aluminum, the density of the glass-ceramics and wear resistance can be improved with their friction coefficient being lowered. Under oil lubrication sliding, the friction coefficient of glass-ceramics decreases and their wear resistance increases extremely, whose reason is that small pores within the glass-ceramics play an role on oil storage.

Abstract: Using high purity solid graphite as a source cathode, purity titanium as the cathode, titanium surface was carburized by a double glow plasma hydrogen-free carburizing. Experimental results indicate that a higher hardness carburized layer, containing higher hardness TiC phase and dissociate state carbon antifriction phase was formed on the titanium surface. The carbon concentration and the hardness of carburized layer distribute in the gradient along the carburized layer. The surface hardness reaches 1000HK. The polarization curve of Ti carburized has the passivation peak of wider range, and corrosion rate of 0.089 is lower than that of Ti(0.225),indicating that corrosion resistance of titanium carburized is higher than that of Ti untreated.