Advanced Materials Research Vols. 399-401

Abstract: The inorganic materials（MoSe₂/C) and MoSe2 were synthesized via solid-state reaction methods and characterized by a series of techniques. The growth process of the products was discussed on the basis of the experimental facts. The tribological properties of MoSe₂/C and MoSe₂ as additives in 150bn basic oil were investigated by UMT-2 multispecimen tribotester. Under the determinate conditions, the friction coefficient of the basic oil containing MoSe₂/C (or MoSe₂) was lower than that of the basic oil. Moreover, the tribological property of the basic oil with the MoSe₂/C was better than that with MoSe₂ nanoflakes. A combination of sliding friction, stable tribofilm and fill in-repair mechanisms on the rubbing surface could explain the good friction and wear properties of MoSe₂/C and MoSe₂ as additives.

Abstract: Different phase compositions and microstructures of oxide scales were formed on the surface of SS400 hot rolled alloys by employing various heat treatment processes. Cyclic wet-dry immersion corrosion test, electrochemical impedance spectroscopy were used to investigate the corrosion resistance of strips with scales fabricated by different heat treatment processes. The results reveal that difference in the corrosion resistance of the various scales is due to the difference in the grain size of Fe₃O₄ phase. Furthermore, the difference in the corrosion resistance of different oxide phases, exhibited by various scales, also render the strips to give various corrosion behaviors. It is surmised that the strip with oxide scale, which consist of a small mount of the outer layer Fe₂O₃ phase distributed continuously and a large quantity of the inner layer Fe₃O₄ phase with the fine grain size, and possess nice compactness, continuity, integrity in the morphology structure, has the best corrosion resistance.

Abstract: Cr-Mo surface alloying modified layers on Ti6Al4V alloy were prepared using double glow discharge plasma alloying technique. The surface hardness and the resistance ability of repeated impact of the layers were measured using Knoop hardness test and repeated impact test respectively. The results show that the surface hardness of the modified samples was significantly improved due to the deposited layer containing Cr_1.93Ti_1.07, Cr₂Ti, FeCrMo, and Cr₂Ti₄O₁₁ compounds. However, it was found that heavy peeling occurred on the Cr-Mo alloying modified layers after repeated impact test due to these brittle phases formed in plasma alloying process. Brittle phases appeared in the surface modified layer, such as intermetallic compounds, contribute to hardness enhancement and wear properties, but may be detrimental to impact resistance.

Abstract: The semiconducting behavior of No.20 carbon steel coated with different polymer coating in 5% sodium hydroxide solution was studied by utilizing potential-capacitance and Mott-Schottky analysis. Results showed that the phenol aldehyde resin and alkyd resin behaved as bipolar film, showed p-type semiconducting behavior at the potential range of -0.3V ~ -0.1V vs. SCE and as an n-type semiconductor at the potential range of 0V ~ 0.4V vs. SCE in 5% sodium hydroxide, whereas for the epoxy resin, it showed as an insulator in 5% sodium hydroxide solution at the same condition.

Abstract: The paper through the synergy before mixed Phytic acid and Sodium molybdate, Sulfosalicylic acid, Organic silane, and add the active substances PEG, Optimize the Passivation liquid formula of Brass surface, Phytic acid is the main ingredient, study the affection of Phytic acid Passive film Corrosion resistance on the three main Passivation conditions: Passivation temperature, time and Passivation solution PH value. The results show that，Phytic acid passivation film process recipes as follows：Phytic acid (quality score 50%) 2~5ml/L, sodium molybdate 4~8g/L, organic material 10~30ml/L, sulfosalicylic acid 3~7g/L, polyethylene glycol 2~6g/L, deactivated temperature 30~35°C, pH value 5, deactivated time 60s. The test showed that，the phytic acid passive film can obviously enhance the anti-corrosive performance on the brass surface, its corrosion resistance proportion chromates passive film is fairly good.

Abstract: In this paper, an organic/inorganic molybdenum series Cr-free coating was formed on galvanized steel by simple immersion and its corrosion behavior was compared to that of a typical chromate coating. Molybdate and 1-Hydroxy-ethylidene-1, 1-diphosphonic acid (HEDP) were used as corrosion inhibitor, as well as acrylic resin and silane were used as film-former and coupling agents, respectively. The corrosion behavior of the coatings was evaluated by Neutral salt spray (NSS), Electrochemical impedance spectroscopy (EIS) and Tafel polarization. The surface topography of the samples was observed by Scanning Electron Microscopy (SEM). The results indicated that the corroded area of the Mo-HEDP treatment was only corroded 2% after 72 h spraying, while the corrosion behaviour of Mo-HEDP was closed to that of Cr pretreatment due to the synergistic reaction of molybdate and HEDP. Compared with the film of Cr treatment, Mo-HEDP passivating coating was more environmentally friendly.

Abstract: A two-dimensional finite element simulation of a welding process is developed for predicting temperature histories and residual stresses in a structural steel butt-welded joint. The purpose of the simulation presented in this paper is the assessment of the effect of uncertainties in thermal material, loading and constraint input on both the thermal and mechanical analysis predictions. The model is validated by comparison with previously welded and tested specimen with published residual stresses measurements. Residual stress results are not sensitive to the thermal analysis input even if the latter has significant influence on temperature distribution. Modelling boundary conditions for both thermal and stress analyses, was identified as a key factor affecting predictions of residual stresses and distortion.

Abstract: Fe-Si layer was prepared on silicon steel substrate from KCl-NaCl-NaF-SiO2 molten salts by pulse current at different time. The quantitative Si concentration depth profile, surface morphology and phase structure of the layer were studied by glow discharge optical emission spectroscopy, atomic force microscopy and X-ray diffraction. The layer growing process was analyzed from nucleation process, growth pattern and microstructure. It was observed that the Fe-Si alloy nucleated in the way of three dimensional conical shape and initially grew in the orientation of matrix, then gradually adjusted to the lowest energy state. With deposition time going on, the phase structure of the layer changed in the order of -Fe (Si) →α-Fe (Si) ＋Fe₃Si →Fe₃Si

Abstract: This article studied on the surface modification of ammonium nitrate by the liquid coating technology , choosing separately polyvinyl acetate (PVAC), sliced paraffin (Wax),polyethylene glycol (PEG) as coating materials. The samples were characterized by SEM and DSC. The experimental results showed that the modification effects of PVAC and Wax were good. The appearance of modified ammonium nitrate presented spherical, and flowing property was better. Their moisture absorption descended respectively by 30.6%, 23.3% after 24 hours at ambient temperature 30°C and relative humidy 75%.

Abstract: Abstract: In contrast to their exceptional mechanical properties, titanium and its alloys possess poor friction and wear characteristics. Nanocrystalline diamond (NCD) films appear to be a promising solution for their tribological problem due to their smooth surfaces and small grain size. However, the synthesis of a well adherent NCD film on titanium and its alloys is always complicated due to the different thermal expansion coefficients of the two materials, the complex nature of the interlayer formed during diamond deposition, and the difficulty in achieving very high nucleation density. In this work NCD thin films have been deposited on pure Ti substrates in a microwave plasma chemical vapor deposition (MWPCVD) reactor under fixed pressure and methane concentration in hydrogen but over a wide temperature range. The effects of depositing temperatures on the adhesion of films are evaluated using Rockwell indentation tests. It is found that by increasing the deposition temperature the films bonding deteriorates. The films synthesized are characterized by field emission scanning electron microscopy, atomic force microscopy, Raman spectroscopy, and X-ray diffraction.