Preparation of Laser Cladding Coating Undercooling Cu-based Alloy and Co on Non-equilibrium Solidification Structure

The effect of the gradient content of Co element on the solidification process of Cu-based alloy under deep under cooling conditions was explored.The non-equilibrium solidification structure of the under cooled alloy samples were analyzed.It is found that the rapidly solidified alloy has undergone twice grain refinement during the undercooling process.Characterization and significance of the maximum undercooling refinement structure of Cu60Ni35Co5 at T=253 K were analyzed.High-density defects were observed,such as dislocations,stacking faults networks,and twinning structures.The standard FCC diffraction pattern represents that it is still a single-phase structure.Based on the metallographic diagram,EBSD and TEM data analysis,it is illustrated that the occurrence of grain refinement under high undercooling is due to stress induced recrystallization.In addition,the laser cladding technology is used to coat Co-based alloy(Stellite12) coating on 304 stainless steel substrate;the microstructure of the coating cross-section was analyzed.It was found that the microstructure of the cross-section is presented as columnar crystals,planar crystals,and disordered growth direction,so that the coating has better hardness and wear resistance.By electrochemical corrosion of the substrate and coating,it can be seen that the Co and Cr elements present in the coating are more likely to form a dense passivation film,which improved the corrosion resistance of the coating.

Effect of Cu addition on the microstructure and tribological performance of Ni60 directional structure coating

The Ni60/15wt% Cu directional structure coating was prepared by the composite technology of flame spraying, induction remelting,and forced cooling, and the effect of Cu on the microstructure, phase, hardness, and wear performance of Ni60 coatings was investigated. Results showed that Cu addition makes the microstructure of Ni60 directional structure coating more compact, and Cu is mainly enriched within the crystal grain, resulting in the formation of Cu_(3.8)Ni as the bonding phase. Compared with Ni60 directional structure coating, Ni60/Cu directional structure coating has a lower hardness, lower friction coefficient, and lower wear rate, which indicate that Cu can effectively enhance the antifriction performance of Ni60 directional structure coating.

Research Progress in the Failure Behavior onthe Interface of Thermal Barrier Coatings

This paper mainly introduces the research progress on interface failure behavior in high-temperature alloy surface thermal barrier coating systems.The degradation failure and structural evolution behavior during high-temperature service were analyzed for the matrix/bonding layer interface,bonding layer/TGO interface,and TGO/ceramic layer interface in thermal barrier coatings.The research focus and direction that affect the interface performance of thermal barrier coatings were proposed.

THE EFFECT OF COMPLIANT COATINGS ON COHERENT STRUCTURE IN TURBULENT BOUNDARY LAYERS

The velocity profile,turbulence intensity profile,streaky structure and bursting frequency in turbulent boundary layers over a flat plate with compliant coatings were investigated by Laser Doppler Anemometry and condi- tional sampling techniques.This experiment led to the conclusions that in boundary layer flows on a compliant wall,as compared with that on a rigid wall,the log law region was extended further away from the wall,and that the maximum value of each turbulence intensity profile in the near wall region was reduced and the bursting frequency obviously decreased with the compliant coatings.One point worthy of notice was that the above results were very much like those of polymer drag reduction experiments.

Microstructure and hot corrosion behavior of Al-Ce-Y coatings on DZ125 nickel-based alloy prepared by pack cementation process

In order to improve the hot corrosion resistance of DZ125 alloy,Ce-Y modified aluminum coatings were prepared on DZ125 alloy by pack cementation process at 950°C for 2 h.The microstructure,phase constitution and formation mechanism of the coatings were investigated.The hot corrosion behaviors of DZ125 alloy and the coatings in molten salt environment of 25%K2SO4+75%Na2SO4(mass fraction)at 900°C were studied.Results show that the obtained Al-Ce-Y coatings were mainly composed of Al3Ni2,Al3Ni and Cr7Ni3,with a thickness of about 120μm.After hot corrosion test,DZ125 alloy suffered catastrophic hot corrosion and serious internal oxidation and internal sulfidation arose.Two layers of corrosion products formed on surfaces of DZ125 alloy,including the outer layer consisting of Cr2O3 and NiCr2O4,and the inner layer of Al2O3,Ni3S2 and Ni-base solid solution.After being coated with Al-Ce-Y coating,the hot corrosion resistance of DZ125 alloy is improved notably,due to the formation of a dense scale mainly consisting of Al-rich Al2O3 in the coating layer.

Structure and Properties of Ti-Si-N Coatings Synthesized by Combining Cathode Arc and Middle-frequency Magnetron Sputtering

Ti-Si-N composite coatings were synthesized on a novel combining cathode and middle-frequency magnetron sputtering system, designed on an industrial scale. Ti was produced from the arc target and Si from magnetron target during deposition. The influences of negative bias voltage and Si content on the hardness and microstructure of the coatings were investigated. The composite coatings prepared under optimized conditions were characterized to be nc-TiN/a-Si3N4 structure with grain sizes of TiN ranging from 8-15 nm and exhibited a high hardness of 40 GPa. The enhancement of the hardness is suggested to be caused by the nanograin-amorphous structure effects.

Microstructure studies of air-plasma-spray-deposited CoNiCrAlY coatings before and after thermal cyclic loading for high-temperature application

In the present study, bond-coats for thermal barrier coatings were deposited via air plasma spraying（APS） techniques onto Inconel 800 and Hastelloy C-276 alloy substrates. Scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, X-ray diffraction（XRD）, and atomic force microscopy（AFM） were used to investigate the phases and microstructure of the as-sprayed, APS-deposited Co Ni Cr Al Y bond-coatings. The aim of this work was to study the suitability of the bond-coat materials for high temperature applications. Confirmation of nanoscale grains of the γ/γ′-phase was obtained by TEM, high-resolution TEM, and AFM. We concluded that these changes result from the plastic deformation of the bond-coat during the deposition, resulting in Co Ni Cr Al Y bond-coatings with excellent thermal cyclic resistance suitable for use in high-temperature applications. Cyclic oxidative stability was observed to also depend on the underlying metallic alloy substrate.

Effect of cermet substrate characteristics on the microstructure and properties of TiAlN coatings

The composition and structure of substrate materials have important influences on coating performance,especially in terms of bond-ing strength and coating hardness,which determine whether the coating can be used for a given application.In this study,a TiAlN coating is deposited on Ti(C,N)-based cermet(TC)substrates with 0wt%-20wt%WC by arc ion plating.The influence of cermet substrate characterist-ics on the structure and properties of the TiAlN coating is then researched.Results show that the TiAlN coating deposited on the TC substrate has a columnar grain structure.As WC increases,the strength ratio of I(111)/I(200)and adhesive strength of TiAlN gradually increases.In the ab-sence of WC in the substrate,the preferred orientation of the TiAlN coating is(200).As WC increases,the preferred orientation of the TiAlN coating becomes(111)and(200).Notable differences in adhesive strength between the coating and substrate could be attributed to the micro-structure and composition of the latter.Scratching results show that the adhesive strengths of the TiAlN coating on the 0wt%-20wt%WC cer-met substrate are 52-65 N.Among the coatings obtained that on the TC substrate with 15wt%WC presents the highest H/E and H3/E2,which indicates that this coating also features the best wear resistance.The failure mechanisms of the coated tools include coating peeling,adhesive wear,and abrasive wear.As the cutting speed increases,the degree of flank wear increases and the durability of the coating decreases accord-ingly.Increases in WC result in an initial decrease followed by a gradual increase in the flank wear of the coated cermet inserts.

The Effect of Unbalanced Coefficient of Magnetron on the Structure and Properties of CN_x Coatings

The effect of unbalanced coefficient of magnetron （UCM） on the structure and tribological properties of CrNx hard coatings was studied.The CrNx coatings were deposited on both Si wafer and hardened tool steel substrates using a closed-field unbalanced magnetron sputtering ion plating technique in a gas mixture of Ar＋N2 under different unbalanced magnetron conditions.The coatings were characterized by means of XRD,XPS,SEM,microhardness tester and pin-on-disc tribometer to study respectively their structure,chemical bonding state,microstructure,hardness and tribological properties.The experimental results show that the UCM has a profound effect on the structure,hardness and tribological properties of the CrNx coatings.With increasing the values of UCM,the dominant phases in the deposited coatings evolved from Cr＋Cr2N to Cr2N＋CrN,the microstructure became denser and the hardness increased;in addition,reduced coefficient of friction and improved wear resistance of CrNx coatings were also observed under a larger UCM.

Structure, indentation and corrosion characterizations of high-silicon Ni-Si nano-composite coatings prepared by modified electrodeposition process

Ni-Si nano-composite coatings with various silicon contents were prepared by a modified electrodeposition process using electrolytes containing ball-milled Si/Ni particles. The effects of the concentration of the ball-milled Si/Ni particles in the electrolyte on the silicon content, structure, microhardness and corrosion behaviors of the coatings were investigated. Scanning electron microscopy and X-ray diffractometry were used for structural characterization. Also, the microhardness and corrosion behaviors of the deposited coatings were evaluated. According to the results, the Si level reaches about 10 wt.% in the coating, which is a significant content of Si incorporation for electrodeposition. It was also found that the crystallite size of the coatings was progressively decreased and the hardness was increased, by increasing the content of Si. Typically, the crystallite size and microhardness of the Ni-10 wt.%Si coating were 0.39 and 2.1 times those of the pure Ni coating, respectively. Also, the results showed that there is an optimal content of Si to meet the best acidic corrosion resistance of the coatings.

Effects of Colloidal Silica Binder on Catalytic Activity and Adhesion of HZSM-5 Coatings for Structured Reactors

HZSM-5 coating using three colloidal silica binders, acidic colloidal silica （ACS）, neutral colloidal silica （NCS） and basic colloidal silica （BCS）, was prepared to study the effect of hinders on their adhesion and catalytic activity. Scanning electron microscopy characterization indicated that the zeolite coating using BCS shows the smoothest surface with higher homogeneity and adherence strength. The specific surface area, relative crystallization and acid site strength of zeolites are also dependent on the binder used. Catalytic cracking of supercritical n- dodecane over the series of zeolite coating with various binders indicated that HZSM-5 coating with BCS exhibits the highest and the most stable catalytic activity compared with other kinds of binders, and also exhibits a stable catalytic activity ascribed to its proper acid property and microstructure.

Structure and properties of electrodeposition RE-Ni-W-B-B_4C-PTFE composite coating

The components, surface and cross sectional morphologies, and the effects of heat treatment temperature on phase structure, hardness, abrasion resistance and oxidation resistance of pulse electrodeposition RE-Ni-W-B-B4C-PTFE composite coatings, were all investigated. The results show that W and B contents increase in the RE-Ni-W-B composite coating by using pulse electrodeposition. RE, PTFE and B4C particles can be co-deposited into the Ni-W-B composite coating, but the amount is very little. X-ray diffraction analysis displays that the RE-Ni-W-B-B4C-PTFE composite coating is mainly amorphous, partially crystallized as-deposited, but it turns into crystalline state and PTFE in the coatings will decompose after the heat treatment temperature is higher than 400℃. The hardness of the composite coating increases with increasing heat treatment temperature, it comes up to the highest value at 400℃. The oxidized film mass of the composite coating increases slowly when the oxidation temperature is lower than 500℃, but it increases linearly and sharply after the oxidation temperature is higher than 600℃.

Structure and characteristics of electrodeposited RE-Ni-W-P-B_4C-PTFE composite coatings

Hardness, friction and wear characteristics of electrodeposited RE Ni W P B 4C PTFE composite coatings were studied, and the reason for these fine characteristics was explained in respect of structure. The results show that 1) the structure of RE Ni W P B 4C PTFE composite coatings experiences a transformation process from amorphous to mixture then to crystal as the heat treatment temperature rises; 2) incorporating of B 4C greatly increases the hardness of the coating; 3) the wear resistance of the coating is best with heat treatment for 1?h at 300?℃, which is greatly superior to that of the other traditional coatings.

Structure,mechanical and thermal properties of Y-doped CrAlN coatings

CrAlYN coatings with different Y contents(0,5 and 12 at.%)were deposited by cathodic arc evaporation to investigate the influence of Y-addition on the structure,mechanical and thermal properties of CrAlN coatings by using X-ray diffraction,scanning electron microscopy,differential scanning calorimetry,thermal gravimetric analysis and nanoindentation.The structural transformation of single phase cubic Cr_(0.42)Al_(0.58)N and Cr_(0.39)Al_(0.56)Y_(0.05)N coatings to cubic−wurtzite mixed Cr_(0.32)Al_(0.56)Y_(0.12)N coating leads to a drop in hardness from(30.2±0.7)GPa of Cr_(0.42)Al_(0.58)N and(32.0±1.0)GPa of Cr_(0.39)Al_(0.56)Y_(0.05)N to(25.2±0.7)GPa of Cr_(0.32)Al_(0.56)Y_(0.12)N.The incorporation of 5 at.%Y retards the thermal decomposition of CrAlN,verified by the postponed precipitation of w-AlN and N-loss upon annealing.Correspondingly,Cr_(0.39)Al_(0.56)Y_(0.05)N coating consistently exhibits the highest hardness value during thermal annealing.Nevertheless,alloying with Y exerts an adverse effect on the oxidation resistance of CrAlN.

A facile method for fabrication of nano-structured Ni-Al_2O_3 graded coatings: Structural characterization

Powder charges of micron-size Ni and Al2O3were utilized to deposit nano-structured Ni-Al2O3composite coatings on analuminum plate fixed at the top end of a milling vial using a planetary ball mill.Composite coatings were fabricated using powdermixtures with a wide range of Ni/Al2O3mass ratio varying from1:1to plain Ni.XRD,SEM and TEM techniques were employed tostudy the structural characteristics of the coatings.It was found that the composition of the starting mixture strongly affects the Al2O3content and the microstructure of the final coating.Mixtures containing higher contents of Al2O3yield higher volume fractions of theAl2O3particles in the coating.Though Ni-Al2O3composite coatings with about50%of Al2O3particles were successfully deposited,well-compacted and free of cracks and/or voids coatings included less than20%(volume fraction)of Al2O3particles which weredeposited from powder mixtures with Ni/Al2O3mass ratios of4:1or higher.Moreover,mechanical and metallurgical bondings arethe main mechanisms of the adhesion of the coating to the Al substrate.Finally,functionally graded composite coatings withnoticeable compaction and integrity were produced by deposition of two separate layers under identical coating conditions.

Influence of Deposition Conditions on the Crystal Structure of MoS_2 Coating

MoS2 coatings were prepared using an unbalanced bipolar pulsed DC （direct current） magnetron sputtering apparatus under different targets, cathode current densities, power modes and bias voltages. The morphology, structure and growth characteristics of MoS2 coatings were observed and identified respectively by scanning electron microscopy, X-ray diffractometry and mass spectrometry. The results show that MoS2 coatings evolve with the （002） basal plane parallel to the surface by using cold pressed target with lower density, lower cathodic current density, bipolar pulse DC power and minus bias voltage, whereas the coatings deposited under hot pressed target, higher cathodic current density, simple DC power and positive bias voltage have the （002） basal plane perpendicular to the surface. The influence of deposition conditions on the crystal structure of MoS2 coating is implemented by altering its growth rate and the energy of sputtering-deposition particles.

Microstructure and Anticorrosion Property of AT13 Coatings Made by Combination of Nanoparticles Doping and Plasma Spraying Technique

Al2O3+13wt%TiO2 (AT13) particles were doped with 5%～30% nanoparticles and prefabricating powders were prepared by renewed granulation. AT13 coatings were prepared on the surface of steel 45# by air plasma spraying technique with the prefabricating powders. The microstructures of the AT13 prefabricating powders and the resulting coatings were investigated by SEM and EDS and XRD. The samples were undergone corrosion in the medium of 10% H2SO4 aqueous solution at temperature 80℃. The results indicate that the blistering time of coatings in the corrosive medium was increased with the increase of doped nanoparticle concentration while the time from blistering to spalling is independent of nanoparticle concentration. The results revealed that the structure of prefabricating powders was a twisted micrometer grade particle with dimension of 40-60μm, encapsulated by nanoparticles. The homogeneity of element distribution in coatings was improved and porosity was reduced. The phases of (Al2O3) 5.333 and orthorhombic Al2TiO5 were identified . The fracture analysis confirmed that there is a large amount of vermiculate whiskers with diameter of 10nm and length of 100～200 nm in coatings and the fracture type of coatings was the ductile trans-granular fracture.

Applicability Evaluation of a Laser Light-Mater Interaction Based Computational Tool on Status Identification of Applied Micro-Structured Coatings

The current work aims at evaluating a proposed method based on a computational tool developed using Object-Oriented Programming to identify the status of micro-structured surfaces. In this case, these are micro-structured coatings with riblet microstructure developed by Fraunhofer Institute–IFAM, by building a graphical reproduction of the analyzed surface and calculating an expected laser reflection intensity acquired by a laser sensor device, the proposed method is assessed by using the simplest case: a flat surface, and an optimal case: an intact riblet surface. The results corroborate the calculations to be applied to further steps from more complex cases of degradation and to diverse riblets geometries. Based on Huygens-Fresnel and Fraunhofer diffraction theories, the calculations developed and demonstrated in this paper improved the nondestructive tests to support the status identification of the micro structured coatings, e.g. riblet structures based on shark skin used in shipping and aerospace industries. This work is assured required quality of the riblet coating identifying the number of structures and expected geometry using implemented calculations to foresee the laser reflection intensity acquired by a laser sensor device with 3 detectors, for instance, a riblet structure could be graphically reproduced, analyzed and completely identified based on the application of the theoretical optics applied on this work.

Effect of Perlite on Fire Protection of Waterborne Coatings for Steel Structure

In this paper, perlite was used as a kind of modifier to prepare waterborne fire resistive coatings for steel structure. The influence of perlite on the properties of the fire resistive coatings was investigated with the help of thermogravimetric analysis (TGA), micro-scale combustion calorimetry (MCC) and fire protection test. The TGA results showed that the char residue weight of the coatings was increased when perlite was loaded and the anti-oxidation performance was enhanced as well and MCC data indicated the addition of perlite reduced the peak heat release rate and total heat release. After the fire protection test, the results confirmed that the fire resistant time of the coating coated with 5 wt% perlite increased up to 114.4 min when the temperature of the sample boards’ backside reached 500?C.

Effect of Inter Stock ‘Zhong ai 1hao'on the Structure of Spindle-shaped 'Huangguan' Pear Trees

In order to investigate the effect of dwarfing inter stock on the structure of pear trees,investigations were made to the tree and group structure of the 4-year-old spindle-shaped‘Huangguan'pear grafted with vigorous stock( Pyrus betulaefolia stock) and that grafted with the dwarfing inter stock‘Zhong ai 1 hao'( P. betulaefolia rootstock). The results showed that the 4-year-old‘Huangguan'pear trees grafted with the dwarfing inter stock‘ Zhong ai 1 hao'were 2. 87 m high on average,with 70. 70% of short braches,converted into 21 016. 0 branches per 667 m^2,840. 64 m^2 of leaf area per 667 m^2 with the leaf area coefficient of 1. 75.On the other hand,for the‘Huangguan'trees grafted with vigorous stocks,the average tree height was 3. 17 m,and the short branch proportion was 63. 20%,converted into 15 806. 4 branches per 667 m^2,719. 28 m^2 of leaf area per 667 m^2 with the leaf area coefficient of 1. 55. Therefore,the use of dwarfing inter stock‘Zhong ai 1 hao'had significant dwarfing effect on‘Huangguan'pear trees,which also showed significant yield increasing effect.