Microstructure and Properties of AlCoCrFeNiTi High-Entropy Alloy Coatings Prepared by Laser Cladding

21-4N(5Cr21Mn9Ni4N)is extensively employed in the production of engine valves,operating under severe conditions.Apart from withstanding high-temperature gas corrosion,it must also endure the impact of cylinder explosion pressure.The predominant failure mode of 21-4N valves is abrasive wear.Surface coatings serve as an effective approach to prevent such failures.In this investigation,Laser cladding technology was utilized to fabricate AlCoCrFeNiTi high entropy alloy coatings onto the surfaces of 21-4N valves.According to the findings,the cladding zone has a normal dendritic microstructure,a good substrate-to-cladding layer interaction,and no obvious flaws.In terms of hardness,the cladding demonstrates an average hardness of 620 HV.The hardness has increased by 140%compared to the substrate.The average hardness of the cladding remains at approximately 520 HV even at elevated temperatures.Regarding frictional wear performance,between 400℃and 800℃,the cladding layer exhibits an average friction coefficient of 0.4,with the primary wear mechanisms being abrasive wear,adhesive wear,and a minor degree of plastic deformation.

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.

Process Parameters Optimization of Laser Cladding for HT200 with 316L Coating Based on Response Surface Method

In order to improve the sealing surface performance of gray cast iron gas gate valves and achieve precise molding control of the cladding layer,as well as to reveal the influence of laser cladding process parameters on the morphology and structure of the cladding layer,we prepared the 316L coating on HT 200 by using Design-Expert software central composite design(CCD)based on response surface analysis.We built a regression prediction model and analyzed the ANOVA with the inspection results.With a target cladding layer width of 3.5 mm and height of 1.3 mm,the process parameters were optimized to obtain the best combination of process parameters.The microstructure,phases,and hardness variations of the cladding layer from experiments with optimal parameters were analyzed by the metallographic microscope,confocal microscope,and microhardness instrument.The experimental results indicate that laser power has a significant impact on the cladding layer width,followed by powder feed rate;scan speed has a significant impact on the cladding layer height,followed by powder feed rate.The HT200 substrate and 316L can metallurgically bond well,and the cladding layer structure consists of dendritic crystals,columnar crystals,and equiaxed crystals in sequence.The optimal process parameter combination satisfying the morphology requirements is laser power(A)of 1993 W,scan speed(B)of 8.949 mm/s,powder feed rate(C)of 1.408 r/min,with a maximum hardness of 1564.3 HV0.5,significantly higher than the hardness of the HT200 substrate.

Ultra wear resistant TiC-Fe coating prepared by high efficient and economic plasma cladding method

The key components of engineering machinery frequently failed due to working in the high load and high wear operating envir-onment.And the performance of the Fe-based alloy coatings typically employed need to be improved for fulfilling the service requirements.Herein,a TiC strengthened Fe-based alloy cladding layer,named TiC-Fe coating,was designed and prepared by plasma cladding technology.The frictional wear performance of coating under various loads was tested.The wear morphology of the coating was observed,and its wear mechanism was examined.The results indicated that the TiC-Fe coating was well formed and metallurgically bonded to the Q345C substrate.Its microstructure mainly consisted of Fe-Cr solid solution,α-Fe phase,(Fe,Cr)_(7)C_(3) phase and TiC phase.The coating exhibited an average microhardness of 980 HV0.2,which was about 5.4 times that of the Q345C substrate.The wear mass loss of the TiC-Fe coatings was much smaller than that of the Q345C substrate,which indicated that the wear resistance of the Q345C coating was superior to the substrate,and the wear mechanism of the coating was mainly attributed to the abrasive wear.

Evaluation of Textured Concrete as an Alternative for Stone as a Cladding Material

Along with the increasing demand on exterior wall cladding as a protective cover for the interior elements and an indicator for modernity and architectural innovation,comes the need to develop new cladding materials that can replace the old ones and overcome their setbacks.This paper discusses the possibility of replacing stone by textured concrete as a cladding material in order to overcome the main challenges faced stone cladding by comparing them together.The comparison was made based on the main requirements of the cladding materials namely:economic,environmental,social,functional and structural aspects.

Fretting Wear Characteristics of Nuclear Fuel Cladding in High-Temperature Pressurized Water

In pressurized water reactor(PWR),fretting wear is one of the main causes of fuel assembly failure.Moreover,the operation condition of cladding is complex and harsh.A unique fretting damage test equipment was developed and tested to simulate the fretting damage evolution process of cladding in the PWR environment.It can simulate the fretting wear experiment of PWR under different temperatures(maximum temperature is 350℃),displacement amplitude,vibration frequency,and normal force.The fretting wear behavior of Zr-4 alloy under different temperature environments was tested.In addition,the evolution of wear scar morphology,profile,and wear volume was studied using an optical microscope(OM),scanning electron microscopy(SEM),and a 3D white light interferometer.Results show that higher water temperature evidently decreased the cladding wear volume,the wear mechanism of Zr-4 cladding changed from abrasive wear to adhesive wear and the formation of an oxide layer on the wear scar reduced the wear volume and maximum wear depth.

Effects of process parameters and annealing on microstructure and properties of CoCrFeMnNi high-entropy alloy coating prepared by plasma cladding

Plasma cladding was used to prepare a CoCrFeMnNi high-entropy alloy(HEA)coating under different conditions.The process parameters were optimized using an orthogonal experiment design based on surface morphology quality characteristics,dilution rate,and hardness.The optimal process parameters were determined through range and variance analysis to be a cladding current of 70 A,a cladding speed of 7 cm·min^(-1),and a powder gas flow rate of 8 L·s^(-1).During the optimized experiments,both the cladded and annealed CoCrFeMnNi HEA coatings exhibit some pores,micro-voids,and a small amount of aggregation.However,the aggregation in the annealed coating is more dispersed than that in the cladded coating.The cladded CoCrFeMnNi HEA coating consists of simple FCC phases,while a new Cr-rich phase precipitates from the FCC matrix after annealing the coating at a temperature range of 550°C-950°C.After annealing at 850°C,the proportion of the FCC phase decreases compared to the cladded coating,and the number of large-angle grain boundaries is significantly reduced.However,the proportion of grains with sizes below 50μm increases from 61.7%to 74.3%.The micro-hardness and wear resistance of the cladded coating initially increases but then decreases with an increase in annealing temperature,indicating that appropriate annealing can significantly improve the mechanical properties of the CoCrFeMnNi HEA coatings by plasma cladding.The micro-hardness of the CoCrFeMnNi HEA coatings after annealing at 650°C increases to 274.82 HV_(0.2),while the friction coefficient decreases to below 0.595.

Transient fuel performance analysis of UO_(2)–BeO fuel with composite SiC coated with Cr cladding based on multiphysics method

The transient multiphysics models were updated in CAMPUS to evaluate the accident-tolerant fuel performance under accident conditions.CAMPUS is a fuel performance code developed based on COMSOL.The simulated results of the UO_(2)–Zircaloy fuel performance under accident conditions were compared with those of the FRAPTRAN code and the experimental data to verify the correctness of the updated CAMPUS.Subsequently,multiphysics models of the UO_(2)–BeO fuel and composite SiC coated with Cr(SiC_(f)/SiC-Cr)cladding were implemented in CAMPUS.Finally,the fuel performance of the three types of fuel cladding systems under Loss of Coolant Accident(LOCA)and Reactivity Insertion Accident(RIA)conditions was evaluated and compared,including the temperature distribution,stress distribution,pressure evolution,and cladding failure time.The results showed that the fuel temperature of the UO_(2) fuel under accident conditions without pre-irradiation was lower after being combined with SiC_(f)/SiC-Cr cladding.Moreover,the centerline and outer surface temperatures of the UO_(2)–BeO fuel combined with SiC_(f)/SiC-Cr cladding reduced further under accident conditions.The cladding temperature increased after the combination with the SiC_(f)/SiC-Cr cladding under accident conditions with pre-irradiation.In addition,the use of SiC_(f)/SiC-Cr cladding significantly reduced the cladding hoop strain and plenum pressure.

Fiber cladding dual channel surface plasmon resonance sensor based on S-type fiber

Fiber cladding surface plasmon resonance(SPR)sensors have few structures,and a clad SPR sensor based on S-type fiber is proposed in this paper.This new type of fiber cladding SPR sensor was formed by electrofusing an S-shaped structure on the fiber to couple the light in the fiber core to the cladding.In this paper,the effects of fiber parameters on the performance of the sensor were studied by simulation and experiment.Based on the conclusion that the smaller the core diameter is,the closer the working band of the SPR resonance is to long wavelengths,and that the geometric characteristics mean that a multimode fiber can receive the fiber cladding light from a small core diameter few-mode fiber,a dual channel SPR sensor with a double S-type fiber cascade was proposed.In the refractive index detection range of 1.333–1.385refractive index units(RIU),the resonant working band of channel I is 627.66 nm–759.78 nm,with an average sensitivity of 2540.77 nm/RIU,and the resonant working band of channel II is 518.24 nm–658.2 nm,with an average sensitivity of2691.54 nm/RIU.The processing method for the S-type fiber cladding SPR sensor is simple,effectively solving the problem of this type of SPR sensor structure and the difficult realization of a dual channel.The sensor is expected to be used in the fields of medical treatment and biological analysis.

A cladding-pumping based power-scaled noise-like and dissipative soliton pulse fiber laser

We report a high-average-power noise-like pulse(NLP) and dissipative soliton(DS) pulse fiber laser. Average power as high as 4.8 W could be obtained at the fundamental mode-locked repetition rate. The NLP can also be transformed into a more powerful DS mode-locking state by optimizing the polarization and losses of intra-cavity pulses in the nonlinear polarization evolution regime. The operation mode between the NLP and DS can be switched, and the laser output performance in both modes has been studied. The main advantage of this work is switchable high-power operation between the NLP and DS. In comparison with conventional single-mode NLP fiber lasers, the multi-function high-power optical source will greatly push its application in supercontinuum generation, coherence tomography, and industrial processing.

Numerical simulation of a truncated cladding negative curvature fiber sensor based on the surface plasmon resonance effect

A refractive index(RI)sensor based on the surface plasmon resonance effect is proposed using a truncated cladding negative curvature fiber(TC-NCF).The influences of the TC-NCF structure parameters on the sensing performances are investigated and compared with the traditional NCF.The simulation results show that the proposed TC-NCF RI sensor has an ultra-wide detection range from 1.16 to 1.43.The maximum wavelength sensitivity reaches 12400 nm/RIU,and the corresponding R^(2)of the polynomial fitting equation is 0.9999.The maximum and minimum resolutions are 2.56×10^(-5)and 8.06×10^(-6),respectively.In addition,the maximum amplitude sensitivity can reach-379.1 RIU^(-1)when the RI is chosen as 1.43.The proposed TC-NCF RI sensor could be useful in biochemical medicine,environmental monitoring,and food safety.

Improvement of material properties and cladded flat product productivity with roll-bonding technology

Taking advantage of the progress of roll-bonding technology, the integrity of the material technology, and the development of the production and examination facilities of all the main carbon steels, stainless steels and specialty alloys in Baosteel, the cladded flat new products, which combined both properties of base material and clad material ,have been developed and produced in large quantities. The product categories includes heavy plates with high alloy content and homogeneous distribution in thickness and carbon steel plates cladded with all kinds of stainless steels ,nickel alloys ,and titanium alloys. The double-sided and single-sided cladding hot roiled strips and cold rolled sheets were also commercially produced. Due to the combined properties of both the cladding material and backing material, all products show obvious improvement in properties when compared with solid material. The comparability with the existing production process and equipment laid a very solid foundation for high productivity.

Microstructure and high temperature tribological behavior of laser cladding Ni60A alloys coatings on 45 steel substrate

The crack-free Ni60 A coating was fabricated on 45 steel substrate by laser cladding and the microstructure including solidification characteristics, phases constitution and phase distribution was systematically investigated. The high temperature friction and wear behavior of the cladding coating and substrate sliding against GCr15 ball under different loads was systematically evaluated. It was found that the coating has homogenous and fine microstructure consisting of γ（Ni） solid solution, a considerable amount of network Ni-Ni3 B eutectics, m^23C6 with the floret-shape structure and Cr B with the dark spot-shape structure uniformly distributing in interdendritic eutectics. The microhardness of the coating is about 2.6 times as much as that of the substrate. The coating produces higher friction values than the substrate under the same load condition, but the friction process on the coating keeps relatively stable. Wear rates of the coating are about 1/6.2 of that of the substrate under the higher load（300 g）. Wear mechanism of the substrate includes adhesion wear, abrasive wear, severe plastic deformation and oxidation wear, while that of the coating is merely a combination of mild abrasive wear and moderate oxidation wear.

Microstructure and wear resistance of laser clad TiB-TiC/TiNi-Ti_2Ni intermetallic coating on titanium alloy

A wear resistant TiB-TiC reinforced TiNi-Ti2Ni intermetallic matrix composite coating（TiB-TiC/TiNi-Ti2Ni） was prepared on Ti-6.5Al-2Zr-1Mo-1V titanium alloy by the laser cladding process using Ti＋Ni＋B4C powder blends as the precursor materials.Microstructure and worn surface morphologies of the coating were characterized by optical microscopy（OM）,scan electron microscopy（SEM）,X-ray diffraction（XRD）,energy dispersive X-ray analysis（EDS） and atomic force microscopy（AFM）.Wear resistance of the coating was evaluated under dry sliding wear test condition at room temperature.The results indicate that the laser clad coating has a unique microstructure composed of flower-like TiB-TiC eutectic ceramics uniformly distributed in the TiNi-Ti2Ni dual-phase intermetallic matrix.The coating exhibits an excellent wear resistance because of combined action of hard TiB-TiC eutectic ceramic reinforcements and ductile TiNi-Ti2Ni dual-phase intermetallic matrix.

Synthesis of Y_2O_3 particle enhanced Ni/TiC composite on TC4 Ti alloy by laser cladding

A Y2O3 particle enhanced Ni/TiC composite coating was fabricated in-situ on a TC4 Ti alloy by laser surface cladding. The phase component, microstructure, composition distribution and properties of the composite layer were investigated. The composite layer has graded microstructures and compositions, due to the fast melting followed by rapid solidification and cooling during laser cladding. The TiC powders are completely dissolved into the melted layer during melting and segregated as fine dendrites when solidified. The size of TiC dendrites decreases with increasing depth. Y2O3 fine particles distribute in the whole clad layer. The Y2O3 particle enhanced Ni/TiC composite layer has a quite uniform hardness along depth with a maximum value of HV1380, which is 4 times higher than the initial hardness. The wear resistance of the Ti alloy is significantly improved after laser cladding due to the high hardness of the composite coating.

High temperature frictional wear behaviors of nano-particle reinforced NiCoCrAlY cladded coatings

The NiCoCrAlY coatings strengthened by three nano-particles with the same addition were prepared on a Ni-base super alloy using laser cladding technique. The dry frictional wear behaviors of the coatings at 500 ℃ in static air were investigated. The comparison was made with the coating without nano-particles. The results show that the wear mechanism of the NiCoCrAlY coatings with nano-particles, like the coating without nano-particles, is the delamination wear due to the strong plastic deformation and oxidative wear. However, the frictional coefficient of the coatings increases and presents the decrease trend with the increase of sliding distance after adding nano-particles. Moreover, the wear rate of the coatings with nano-particles is only 34.0%-64.5% of the coating without nano-particles. Among the three nano-particles, the improvement of nano-SiC on the high temperature wear resistance of the coating is the most significant.

Effect of heat treatment on microstructure and mechanical property of Ti-steel explosive-rolling clad plate

The effect of heat treatment on microstructure and mechanical properties of the Ti-steel explosive-rolling clad plate was elaborated by optical microscopy （OM）, scanning electron microscopy （SEM）, X-ray diffraction （XRD）, transmission electron microscopy （TEM）, micro-hardness test and shear test. The composites were subjected to heat treatment at temperature of 650-950 ~C for 60 min. The results show that the heat treatment process results in a great enhancement of diffusion and microstructural transformation. The shear strength decreases as the treatment temperature increases. Heated at 850 ℃ or below, their shear strength decreases slowly as a result of the formation of TiC in the diffusion interaction layer; while at the temperature of 850 ℃ or above, the shear strength decreases obviously, which is the consequence of a large amount of Ti-Fe intermetaUics （Fe2Ti/FeTi） along with some TiC distributing continuously at diffusion reaction layer.

Microstructure and tribological properties of laser cladding Fe-based coating on pure Ti substrate

Fe-based coating was produced on pure Ti substrate by the laser cladding technology. The composition and microstructure of the fabricated coating were analyzed by scanning electron microscopy （SEM）, X-ray diffraction （XRD） and transmission electron microscopy （TEM） technique. The tribological properties were tested through sliding against AISI52100 steel ball at different normal loads and sliding speeds. Besides, the morphologies of the worn surfaces and wear debris were analyzed by scanning electron microscopy （SEM） and three dimensional （3D） non-contact surface mapping. The results show that the prepared Fe-based coating has a high hardness of about 860 HV0.2 and exhibits an average wear rate of （0.70-2.32）×10-6 mm3/（N-m）, showing that the Fe-based coating can greatly improve the wear resistance of pure Ti substrate. The wear mechanism of the coating involves moderate adhesive and abrasive wear.

Bonding properties of interface in Fe/Al clad tube prepared by explosive welding

A Fe/Al clad tube was prepared by explosive welding.Then the bonding characteristic of the interface was investigated by compression,flattening and compression-shear test.The test results exhibit that the clad tubes possessing good bonding interface have higher shear strength than that of pure aluminum and can bear both axial and radial deformation.The original interface between aluminum layer and ferrite layer was observed by scanning electron microscopy（SEM）.The results show that the clad tubes with good bonding properties possess the interface in wave and straight shape.The Fe/Al clad tube was used to manufacture the T-shape by hydro-bulging.It is found that the good-bonding interface of the Fe/Al clad tube plays a dominant role in the formation of the T-shape.

Effects of Fe-Al intermetallic compounds on interfacial bonding of clad materials

The growth of intermetallic compounds at the interface between solid Al and Fe and the effects of intermetallic compound layers on the interfacial bonding of clad materials were investigated. The results showed that the interface between the solid Fe and Al formed by heat-treatment consisted of Fe2Al5 and FeAl3 intermetallic compound layers, which deteriorated the interfacial bonding strength. Fractures occurred in the intermetallic compound layer during the shear testing. The location of the fracture depended on the defects of microcracks or voids in the intermetallic compound layers. The microcracks in the intermetallic compound layer were caused by the mismatch of thermal expansion coefficients of materials during cooling, and the voids were consistent with the Kirkendall effect. The work will lay an important foundation for welding and joining of aluminum and steel, especially for fabrication of Al-Fe clad materials.