•The sulfide film transformation at the initial immersion stages.•The effects of the sulfide film on electrochemical corrosion behavior.•Galvanic effect between fresh steel and sulfide-film-covered steel electrodes.The corrosion products and electrochemical corrosion behavior of X80 pipeline steel in saline solution with saturated H2S at 50 °C were evaluated. The results showed that mackinawite and cubic FeS were the primary and secondary crystalline phases observed and that a series of changes in the size, shape, thickness, and chemical composition occurred as the immersion stages developed. Electrochemical results showed that the sulfide film hindered pitting and enhanced the corrosion resistance definitely. Zero-resistance ammeter measurements showed that the sulfide film repaired itself when local failure occurred.

The age hardenable AA6061-T6 plate was butt welded by friction stir welding. The total heat input, generated by friction between the tool and work piece and plastic deformation, results in a consumption of meta-stable phases in the nugget zone. Precipitation phenomena were closely related to the diffusion of the solute atoms. The existence of special grain boundaries like Σ1a and Σ3 will increase the difficulty in diffusion, which will improve the hardness in the nugget zone. Furthermore, the formation of Σ3 grain boundaries can result from an impingement of re-crystallized grains coming from texture components in twin relationship already. An appropriate strain level may benefit the development of the twin components with a similar intensity. The welding parameters have an effect on heat source mode and the strain level. Then, the type of dynamic re-crystallization and distribution of the special grain boundaries was altered by changing the parameters.

•Fe–Ti–V–Cr–C–CeO2 cladding layer without defects such as cracks and pores.•The phases of the cladding layer were α-Fe, γ-Fe, TiC, VC and TiVC2.•Microstructures of the cladding layer were lath martensite and retained austenite.•The carbide was a complex composed of nano TiC, VC and TiVC2.•The cladding layer possessed good wear and corrosion resistance.In situ TiC–VC reinforced Fe-based cladding layer was obtained on low carbon steel surface by laser cladding with Fe–Ti–V–Cr–C–CeO2 alloy powder. The microstructure, phases and properties of the cladding layer were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), transmission electron microscopy (TEM), potentio-dynamic polarization and electro-chemical impedance spectroscopy (EIS). Results showed Fe–Ti–V–Cr–C–CeO2 alloy powder formed a good cladding layer without defects such as cracks and pores. The phases of the cladding layer were α-Fe, γ-Fe, TiC, VC and TiVC2. The microstructures of the cladding layer matrix were lath martensite and retained austenite. The carbides were polygonal blocks with a size of 0.5–2 μm and distributed uniformly in the cladding layer. High resolution transmission electron microscopy showed the carbide was a complex matter composed of nano TiC, VC and TiVC2. The cladding layer with a hardness of 1030 HV0.2 possessed good wear and corrosion resistance, which was about 16.85 and 9.06 times than that of the substrate respectively.

Traditional welding methods are limited in low heat input to workpiece and high welding wire melting rate. Twin-wire indirect arc(TWIA) welding is a new welding method characterized by high melting rate and low heat input. This method uses two wires: one connected to the negative electrode and another to the positive electrode of a direct-current(DC) power source. The workpiece is an independent, non-connected unit. A three dimensional finite element model of TWIA is devised. Electric and magnetic fields are calculated and their influence upon TWIA behavior and the welding process is discussed. The results show that with a 100 A welding current, the maximum temperature reached is 17 758 K, arc voltage is 14.646 V while maximum current density was 61 A/mm2 with a maximum Lorene force of 84.5 μN. The above mentioned arc parameters near the cathode and anode regions are far higher than those in the arc column region. The Lorene force is the key reason for plasma velocity direction deviated and charged particles flowed in the channel formed by the cathode, anode and upper part of arc column regions. This led to most of the energy being supplied to the polar and upper part of arc column regions. The interaction between electric and magnetic fields is a major determinant in shaping TWIA as well as heat input on the workpiece. This is a first study of electromagnetic characteristics and their influences in the TWIA welding process, and it is significant in both a theoretical and practical sense.

•The local atomic structure of annealed Ni–P amorphous alloys was analyzed.•The improvement of corrosion resistance is in agreement with decreasing order cluster size.•The homogeneity of elements is considered the key affected corrosion resistance.Amorphous Ni–P alloys were prepared via electroless plating and annealing at 250 °C at different times to obtain different microstructures. The local atomic structure of annealed Ni–P amorphous alloys was analyzed by calculating the atomic pair distribution function from the XRD patterns. Corrosion resistance in 0.5 M H2SO4 was investigated via electrochemical techniques. The results indicated that the improvement of corrosion resistance is in agreement with decreasing order cluster size. The order cluster size of annealed Ni–P amorphous alloys initially decreased then increased with increasing annealing time. By contrast, corrosion resistance showed an opposite trend.

The effects of CeO2 on microstructure and corrosion resistance of TiC-VC reinforced Fe-based laser cladding layers were investigated. The results showed that carbides presented in cladding layers were TiVC2 and VC. A small quantity of CeC appeared with 2.0 wt.% CeO2 addition. The amount of lamellar pearlite increased while the amount of residual austenite decreased with increasing CeO2 addition. The corrosion resistance of cladding layers increased firstly and then decreased with the addition of CeO2 increasing. The EIS spectrum of the cladding layer without CeO2 was composed of an inductive arc at low frequency and a capacitive arc at high frequency. The cladding layer with 0.5 wt.% CeO2 addition showed the best corrosion resistance, and then the inductive arc at low frequency transformed into a capacitive arc.Different CeO2 addition has an important effect on microstructure of cladding layers. The amount of lamellar pearlite increased while the amount of residual austenite decreased with increasing CeO2 addition. Secondary electron imaging of cladding layers: (a) cladding layer without CeO2 addition; (b) cladding layer with 1.0% CeO2 addition; (c) cladding layer with 2.0% CeO2 addition; (d) Part A in (c) magnified 10000 times

Novel Ti3AlC2 wicks with two distinguished characteristic pore sizes were successfully developed. The heat transfer performances of the loop heat pipes with monoporous and biporous Ti3AlC2 wicks were comparatively studied. Results show that Ti3AlC2 wicks exhibit increased porosity and reduced thermal conductivity by using salt leaching pore-forming and two kinds of pores can be found in one Ti3AlC2 wick. Moreover, the loop heat pipe with biporous Ti3AlC2 wick operates reliably under the heat load of 25 W compared with that employing monoporous Ti3AlC2 wick. Biporous Ti3AlC2 wicks proved to be possible alternatives to metals and conventional ceramics for applications in LHP wicks.Highlights► Ti3AlC2 with two distinguished characteristic pore sizes were successfully developed. ► LHP with biporous Ti3AlC2 operated reliably compared with that using monoporous wick. ► Ti3AlC2 proved to be possible alternatives to metals for applications in LHP wicks.

The aim of this study is to investigate the effect of forming pressure and microcrystalline cellulose addition on porosity and pore size distribution of the sintered porous wick and combined with a porosity control method developed in this study so that pore properties of sintered porous wick can be well controlled to meet the requirements of loop heat pipe application during its preparation. The porous wicks are prepared by powder metallurgy method with microcrystalline cellulose as space-holder. The result shows that porosity increases about 6.32% when forming pressure decreases 10 MPa and increases about 6.64% when microcrystalline cellulose addition increases 10 wt.%. The pore size distribution ranges become wider and the mean pore diameters increase as the increasing space-holder addition. The error of porosity was less than 6% in the case study that used the porosity control method to fabricate porous wicks with the expected porosity of 75%. The capillary pumping performances were different while both thermal conductivities and porosities of the porous wicks prepared by the porosity control method were the same. Capillary pumping performance can be considered as the balance of the capillary force and the flow property and it is better than permeability in evaluating the performance of porous wick for loop heat pipe. It is suggested that low forming pressure (low space-holder addition) should be used in order to get good capillary pumping performances when fabricating porous wicks with the same porosity for loop heat pipe.The effects of forming pressure and microcrystalline cellulose addition on porosity and pore size distribution of the sintered porous wick are investigated and combined with a porosity control method so that pore properties of sintered porous wick can be well controlled to meet the requirements of loop heat pipe application during its preparation.

The Ni–P coatings with different contents of nanocrystalline phase were prepared by electroless plating. Crystallization fouling adhering experiments indicated that these electroless Ni–P coatings have better anti-fouling property than that of un-coated sample. The effect of microstructure on anti-fouling property of Ni–P coatings is that the adhering amount of crystallization fouling increased with the increasing of nanocrystalline phase. It is considered that the degree of crystallization fouling adhesion is related to the corrosion resistance of the sample. The amorphous Ni–P coating with excellent corrosion resistance is not easy to form “transitional interface” connecting fouling and matrix.

•Ni–Cu–P coating has a larger ordered atomic cluster than Ni–P coating.•Ni–Cu–P has higher exothermic temperature and crystallization activation energy.•Adding Cu to Ni–P coating decreases its corrosion rate.•The ordered cluster size is not the only factor affecting corrosion resistance.Ni–P and Ni–Cu–P amorphous coatings were prepared by electroless plating. The effect of Cu addition on the microstructure, thermal stability, and corrosion resistance of Ni–P amorphous coating was investigated. Results showed that Ni–Cu–P coating has higher corrosion resistance and thermal stability than Ni–P coating. Although the ordered cluster size of Ni–Cu–P amorphous coating is larger than that of Ni–P coating, the corrosion resistance of Ni–Cu–P is superior to that of Ni–P binary coating. This result indicates that aside from cluster size, the composition also affects the corrosion resistance of amorphous materials.