Passivation process of X80 pipeline steel in bicarbonate solutions

The passivation process of X80 pipeline steel in bicarbonate solutions was investigated using potentiodynamic, dynamic electro-chemical impedance spectroscopy （DEIS）, and Mott-Schottky measurements. The results show that the shape of polarization curves changes with concentration. The critical ＇passive＇ concentration is 0.009 mol/L for X80 pipeline steel in bicarbonate solutions. No anodic current peak exists in solutions when the concentration is lower than 0.009 mol/L, whereas there are one and two anodic current peaks when the concentration ranges from 0.009 to 0.05 mol/L and is higher than 0.1 mol/L, respectively. DEIS measurements show that there exist active dissolution range, transition range, pre-passive range, passive layer formation range, passive range, and trans-passive range for X80 pipeline steel in the 0.1 mol/L solutions. The results of DEIS measurements are in complete agreement with the potentiodynamic diagram. An equivalent circuit containing three sub-layers is used to explain the Nyquist plots in the passive range. Analyses are well made for explaining the corresponding fitted capacitance and impedance. The Mott-Schottky plots show that the passive film of X80 pipeline steel is an n-type semiconductor, and capacitance measurements are in good accordance with the results of DEIS experiment.

Comparison of flow behaviors of near beta Ti-55511 alloy during hot compression based on SCA and BPANN models

The flow behavior of Ti-55511 alloy was studied by hot compression tests at temperatures of 973−1123 K and strain rates of 0.01−10 s^(−1).Strain-compensated Arrhenius(SCA)and back-propagation artificial neural network(BPANN)methods were selected to model the constitutive relationship,and the models were further evaluated by statistical analysis and cross-validation.The stress−strain data extended by two models were implanted into finite element to simulate hot compression test.The results indicate that the flow stress is sensitive to deformation temperature and strain rate,and increases with increasing strain rate and decreasing temperature.Both the SCA model fitted by quintic polynomial and the BPANN model with 12 neurons can describe the flow behaviors,but the fitting accuracy of BPANN is higher than that of SCA.Sixteen cross-validation tests also confirm that the BPANN model has high prediction accuracy.Both models are effective and feasible in simulation,but BPANN model is superior in accuracy.

The Aging Behavior of Polyurethane Adhesive in Medium

The aging behavior of polyurethane adhesive in medium was investigated and compared by means of scanning electronic microscopy（SEM）, infrared spectroscopy（IR）, interface analysis and shearing strength test. The experimental results show that the shear strength of polyurethane adhesive in salt water is decreased more quickly than that in water. Na^＋ and Cl^- ions could make the polyurethane adhesive age faster and the interface metal corrosion. The high temperature accelerates the diffusion of water molecule, Na^＋ and Cl^- ions and the degradation of the giant molecule.

The Effect of Relative Humidity on the Corrosion-resisting Property of Fluorocarbon Coating

The effect of relative humidity on the corrosion-resisting property of fluorocarbon coating was investigated by water vapor transmission technique and electrochemical impedance spectroscopy technique. Measuremerits were carried out on samples, which were tested in an accelerated corrosion environment for the same time （300, 500, 800 and 1000 h ）. The experimental results were obtained as follows： （i） The water absorption, coating resistance and corrosion rate of metal under the coating changed with relative humidity and aging time, the results obtained by EIS are good consistent with those by water vapor transmission technique ; （ ii ） when the subject investigated presented two time constant, the goodness of fit by EEC R （ C （ R （ CR ） ） ） was inferior to that by EEC R（ C（ R（QR） ） ）, but the error of parameters acquired from the former was smaller, by which we could analyze the experiment result quantitatively. With the appearance of diffusion layer on the metal, the difference of metal capacitance was aggravated, the error of parameters acquired from EEC R（ C（ R（ C（RW） ） ） ）was bigger than that from EEC R（ C（ R（ Q（ RW） ） ） ） .

Tribological behaviors of spot-textured TiN coatings on M2 high-speed steel under boundary lubricated conditions

The effect of sliding duration on the tribological behaviors of spot patterned coatings was investigated. Two patterns based on physical vapor deposition （PVD） TiN coatings were used, such as, in-lined （IN） and staggered （ST） spots. The tribological behaviors were evaluated by using a Cameron-Plint wear test rig. The M2 steel discs deposited TiN coatings with IN and ST patterns slid against the ASSAB 17 tool steel pins at a speed of 0.23 m/s, in Shell Tellus T32 lubricant and were loaded with 900 N. The testing results on disc specimens with two types of PVD TiN spot patterns, all coated with a bias voltage of-180 V and slid for 4, 8 and 11 h respectively, were presented. The results revealed that the in-lined coatings possessed relatively better wear behaviors than the staggered pattern coatings. Mechanisms for such superiority and for the cause of peeling were discussed. A relevant design approach was suggested for the application of such patterned coatings.

Effect of Cl^-Concentration on the Corrosion Behavior of 16Mn Steel in Saturated H2S/CO2 Solution

The corrosion behavior of 16Mn steel was studied in saturated H2S or H2S/CO2 solutions containing different Cl^-concentrations at 80℃.The microstructure and chemical composition of the corrosion products were investigated through scanning electron microscopy,energy-dispersive X-ray spectroscopy,EPMA,and X-ray diffraction.Results showed that the corrosion rate decreased with increasing Cl^-concentration in saturated H2S or H2S/CO2 solution at pH 4.Conversely,the corrosion rate increased with increasing Cl^-concentration in saturated H2S solution at pH 6.The relative H^＋concentration decreased because of the increase of Cl^-concentration at pH 4,and Cl^-acted as a catalyst in the corrosive medium at pH 6 because the net H^＋concentration decreased obviously compared with the condition at pH4.Cl^-promoted the formation of Fe-deficient iron sulfide at pH 4,and the opposite effect was observed in the nearly neutral solution.The corrosion rate increased firstly with increasing Cl^-concentration and then decreased in the saturated H2S/CO2solution at pH 6.The corrosion products were mainly composed of two kinds of iron sulfide.Sulfide FeS（1-x） was a kind of tetragonal crystal,whereas the other was the hexagonal/monoclinic iron sulfide Fe（1-x）S.The corrosion film that was mainly composed of FeS（1-x） did not confer a protective effect on the base metal.The atomic ratio of Fe/S was more than 1 for FeS（1-x）.The appearance of sulfide FeS（1-x） resembled a square block or small,needlelike,flocculent particles.The atomic ratio of Fe/S was less than 1 for Fe（1-x）S,and the corrosion film mainly composed of Fe（1-x）S conferred some protective property on the base metal.The sulfide FeS（1-x） exhibited a long claviform morphology with a hexagonal or quadrilateral cross-sectional shape.

Microstructure characteristics of Ni/WC composite cladding coatings

A multilayer tungsten carbide particle（WCp）-reinforced Ni-based alloy coating was fabricated on a steel substrate using vacuum cladding technology.The morphology,microstructure,and formation mechanism of the coating were studied and discussed in different zones.The microstructure morphology and phase composition were investigated by scanning electron microscopy,optical microscopy,X-ray diffraction,and energy-dispersive X-ray spectroscopy.In the results,the coating presents a dense and homogeneous microstructure with few pores and is free from cracks.The whole coating shows a multilayer structure,including composite,transition,fusion,and diffusion-affected layers.Metallurgical bonding was achieved between the coating and substrate because of the formation of the fusion and diffusion-affected layers.The Ni-based alloy is mainly composed of y-Ni solid solution with finely dispersed Cr7C3/Cr（23）C6,CrB,and Ni＋Ni3Si.WC particles in the composite layer distribute evenly in areas among initial Ni-based alloying particles,forming a special three-dimensional reticular microstructure.The macrohardness of the coating is HRC 55,which is remarkably improved compared to that of the substrate.The microhardness increases gradually from the substrate to the composite zone,whereas the microhardness remains almost unchanged in the transition and composite zones.

Wear mechanism of electrodeposited amorphous Ni-Fe-P alloys

The wear mechanism of amorphous Ni-Fe-P coating was discussed. The wear resistance of the amorphous Ni-Fe-P coatings was tested on a Timken wear apparatus, and the wear track of the amorphous Ni-Fe-P coatings as-deposited and heated at various temperatures was observed by SEM. The results show that the wear resistance reaches a maximum value at NaHPO2·H2O concentration of 5 g/L, and heating at 400 ℃. The wear mode of the coating will change with the heating temperature increasing from pitting+plowing at 200 ℃ to pitting at 400 ℃, and to plowing at 600 ℃. The pits on the worn surface of the amorphous Ni-Fe-P coating result from the tribo-fatigue fracture. The cracks of spalling initiate at pits and propagate at certain angle with the sliding direction on surface, and then extend into sub-surface along the poor P layers or the interface between layers. Finally under repeated action of the stress in the rubbing process the cracks meet and the debris forms. The generation of the pits and spalling is related with the internal stress, brittleness and layer structure of the amorphous Ni-Fe-P coating.

Development of Atmosphere-controlled Tribometer and Fail-safe Analysis

The design of existing tribometer mainly focuses on normal pressure and environmental conditions, and aims to measure the effect of load and speed on material performance. The effect of gas pressure and environmental condition on performance of materials is usually not considered. Thus, data from friction tests are not precise. In this paper, a new atmosphere tribometer is developed to study the tribological behavior of materials under severe rugged atmosphere. A fail-safe analysis is performed through reproducibility, comparability, and sensitivity tests. The tribometer allows tests to be performed in block-circle disc line contact, pin-circle disc line contact, and block-circle disc face contact configurations at controlled atmosphere and gas pressure. A self-centering plant is designed to settle the poor contact problem. A pin-on-disk test is conducted, and the test results indicate that the proposed design is efficient. A combined sealing style is introduced to control gas leaks. Compared with other sealing styles, the combined sealing is found to meet the experiment requirements best. And the reproducibility, comparability, and sensitivity tests validate the performance of the tribometer. The designed atmosphere tribometer reliably simulates the friction test under extremely harsh conditions, enhances the ability for material tribological properties test, and ensures accuracy of the tribological data.

Properties of Low Surface Energy Fluorocarbon Polymers with Fluoro-acrylic Resins

The low surface energy fluorocarbon polymer from the synthesized fluoro-acrylic resins was developed. Then the molecule orientation principle of nonpolar and polar functional groups in the polymers was analyzed. And the contact angles of pure water drops on the surfaces of various fluoro-monomer homopolymers and interpolymers were measured. So the relation of polymers＇ fluoro-content with the surface energy was determined. The distribution of fluoric functional groups in the polymers was investigated. And the test results show that though the total fluorine content of the fluorocarbon polymers is relative few, their surface energy is really low due to the enrichment of fluoro-chains on the polymers surface.

Evalution of Thermal Oxidative Degradation of Trimethylol-propane Trioleate by TG/DTA/DSC

In order to evaluate the thermal oxidation degradation behavior of lubricant with different antioxidants,the thermal kinetics equation based on the anlyses of thermogravimetry(TG),differential thermal analysis(DTA),and differential scanning calorimetry(DSC)was established,respectively,to calculate the activation energy of lubricant thermal-oxidative reaction.The thermal analyses of TG and DTA were employed to determine the thermal decomposition properties of ester oils trimethylolpropane trioleate(TMPTO)with butyl-octyl-diphenylamine/octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate/amine-phenol combination antioxidant.The activation energy of the lubricating oil adding antioxidant is increased relative to the TMPTO base oil,and the order of activation energy are Ec(93.732 kJ·mol^(-1))>Ed(88.71 kJ·mol^(-1))>Eb(58.41 kJ·mol^(-1))>Ea(46.32 kJ·mol^(-1)).The experimental results show that octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate in TMPTO has favorable resistance to thermal oxidation and decomposition.The thermal analysis method of DSC accurately reflects the heat exchange of lubricant thermal-oxidative reaction.The order of activation energy is calculated to ED(144.385 kJ·mol^(-1))>EC(110.05 kJ·mol^(-1))>EB(97.187 kJ·mol^(-1))>EA(66.02 kJ·mol^(-1)).It is illustrated that the amine-phenol combination antioxidant has the best thermal oxidation resistance,which is the same as what the oxidation onset temperature effected.

Tribological Properties of DLC Film Prepared by C^+ Ion Beam-assisted Deposition (IBAD)

C ^＋ ion beam-assisted deposition was utilized to prepare deposit diamond-like carbon （ DLC ） film. With the help of a series of experiments such as Raman spectroscopy, FT-IR spectroscopy, AFM and nanoindentation , the DLC film has been recognized as hydrogenated DLC film and its tribologicul properties have been evaluated. The bull-on-disc testing results show that the hardness and the tribologicul properties of the DLC film produced by C^ ＋ ion beam- assisted deposition are improved significantly. DLC film produced by C ^＋ ion beam- assisted deposition is positive to have a prosperous tribologicul application in the near future.

Tribological Characteristics of Chromium-active Carbon Electroplated Composite Coatings

A process of chromium electroplating using a standard bath with additives and active carbon particles was reported,and the tribological behaviors of the composite coatings using the pin-on-disk tester and the table wear tester were investigated.Experimental results indicate that the electroplated chromium-active carbon composite coatings exhibited the low friction coefficient and excellent anti-wear properties when compared with the normal chromium electroplated ones.The formation of active carbon particles within the chromium matrices can be explained by SEM analysis and the mechanisms of wear resistance of the composite coatings were studied.

Characterization of gradient Ni-Fe/SiC composite coating on mild steel by thermal spraying in combination with laser cladding

Metal matrix composite coating Ni-Fe/SiC was prepared on an iron-based substrate bythermal spraying combined with laser cladding,using SiC particulates as the reinforcing agent.The micro-structures of the coatings formed at different thermal spraying and laser cladding conditions were character-ized by means of X-ray diffraction and electron probe microanalysis.The thermal oxidation properties of themixed powders composed of different content of SiC particulates and relevant Ni-based alloy as the balancewere examined using differential scanning calorimetry.The hardness profile of the thermal sprayed and lasercladding coatings was investigated as well.It was found that SiO2particulates were generated and dissolvedand dispersed during the melting and solidification of the laser cladding process,which was ascribed to theoxidation of the dispersed SiC particulates.The micro-hardness depth profile of the target laser claddingcomposite coating was characterized by gradient distribution,which could be related to the gradient distribu-tion of the hard SiC and SiO2particulates in the dendrites and interdendrites of the cladding layer.Both SiCand SiO2particulates contributed to greatly increasing the microhardness and mechanical properties of the ti-tled laser cladding composite coatings.

Wear Performance of Ni/ZrO_2 Infiltrated Composite Layer

The Ni/ZrO2 was used as raw materials to fabricate the surface infiltrated composite layer with 1-4 mm thickness on cast steel substrate through vacuum infiltrated casting technology. The microstructure indicated that the infiltrated composite layer included surface composite layer and transition layer. Wear property was investigated under room temperature and 450 ~C. The results indicated that the abrasion volume of substrate was 8 times that of the infiltrated composite layer at room temperature. The friction coefficient of infiltrated composite layer decreased with the increasing load. The wear resistance of infiltrated composite layer with different ZrO2 contents had been improved obviously under high temperature. The friction coefficient of infiltrated composite layer was decreased comparing with that at room temperature. The oxidation, abrasive and fatigue abrasion was the main wear mechanism at room temperature. Oxidation abrasion, fatigue wear and adhesive wear dominated the wearin~ process under elevated temperature.

Preparation and Tribological Performance of Novel Organotin Compound as Lubricant Additive

Oil-soluble stannous naphthenate (SN) is synthesized by using naphthenatic acid and SnO. And its molecular structure is confirmed by IR and multielement oil analyzer (MOA). The tribological performances of the organotin as lubricant additive are evaluated with a four-ball friction and wear tester. These experiments indicate that the wear scar diameter (WSD) and friction coefficient are diminished while the load-carrying capability increased by comparison with that of base oil. The elemental composition of the boundary lubricating film is examined by means of Auger electron spectroscopy (AES). Synergistic effect is found in the load-carrying capability of the complex of SN and sulfured olefin. The analytical results of AES indicate that the good performance of stannous naphthenate is attributed to the formation of a boundary lubricating film containing Sn on the rubbed surface.

Triboelectric behaviors of materials under high speeds and large currents

Using special testers,the triboelectric behaviors of several materials were investigated in this paper under the conditions of high speeds and large currents.The obtained results revealed that the tribological behaviors and current-conducting characteristics have complicated interrelationships.Worsening in the servicing conditions can obviously deteriorate the tribological as well as electrical behaviors;high sliding speeds and large electrical currents can worsen the tribological and electrical conductivity properties,while an appropriate contact pressure can benefit the electrical contact properties.Further analyses reveal that the worsening effects of the above factors,such as frictional heat,arc discharge,arc heat,and surface morphology,result in poor triboelectric contact performance.Among these,the electric arc is one of the most serious factors,because the occurrence of an electric arc may cause severe oxidation,melting,and roughening of the contact surface,thereby causing deterioration in the current-conducting quality as well as material loss.

Nanomaterials for lubricating oil application:A review

Friction and wear are ubiquitous,from nano-electro-mechanical systems in biomedicine to large-scale integrated electric propulsion in aircraft carriers.Applications of nanomaterials as lubricating oil additives have achieved great advances,which are of great significance to control friction and wear.This review focuses on the applications of nanomaterials in lubricating oil and comprehensively compares their tribological characteristics as lubricating oil additives.Statistical analysis of tribology data is provided and discussed accordingly;moreover,the interaction between nanomaterials and sliding surface,lubricating oil,other additives,and synergistic lubrication in nanocomposites are systematically elaborated.Finally,suggestions for future research on nanomaterials as lubricating oil additives are proposed.Hence,this review will promote a better fundamental understanding of nanomaterials for lubricating oil application and help to achieve the superior design of nanoadditives with outstanding tribological performances.

Tribological and economic evaluation of recycled mineral lubricating oils

Seven kinds of used mineral lubricating oils,including hydraulic oils,film bearing oils,steam turbine oil and gear oils,were recycled by reclamation and adding additives.Physical and chemical properties of the recycled oils were measured and their lubrication performances were evaluated by the original and modified four-ball testers.Worn surfaces were analyzed by energy dispersive X-ray spectroscopy and Raman microscope.The recycling costs of burning,re-refined and refortified were estimated.Results showed that physical and chemical properties of the refortified oils were improved effectively and became in the industrial access standard.With the different friction materials under different loads,refortified oils provided excellent lubrication performances,much better than those of fresh oils.Because of additives replenished,the different lubrication films could form on the worn surfaces.A rough financial calculation revealed that the refortification process could produce the most economic value among the three methods.

Thermal-oxidation mechanism of dioctyl adipate base oil

The ester base oil of dioctyl adipate (DOA) was oxidized in an oven at 200 degrees C for 30 h, and variations in the physicochemical and tribological properties were studied. To investigate the thermal-oxidation mechanism, the thermal-oxidation products were analyzed by gas chromatography-mass spectrometry (GC-MS), and the thermal-oxidation process was simulated using visual reactive force field molecular dynamics (ReaxFF MD). The results indicated that the total acid number (TAN) increased significantly because of the presence of 14% carboxylic acids and low molecular weight monoesters. The tribological properties were improved by the formation of the strongly polar carboxylic acids. Additionally, the increase in kinematic viscosity was limited due to the formation of high molecular weight polymerization products and low molecular weight degradation products. Thermal-oxidative degradation and polymerization mechanisms were proposed by combining ReaxFF MD simulations and GC-MS results.