Microstructures and properties of Fe-Co-B-Si-Nb coating prepared by laser cladding and remelting

High power laser cladding of [ （ Fe0. 5 Co0. 5 ） 0. 75 B0. 2 Si0.05 ] 95. 7 Nb4. 3 powder mixture afier-remelting was performed to fabricate Fe-based metallic glass coating on the surface of steel of China Classification Society： Grade B （CCS-B）. Scanning electron microscopy （SEM）, X-ray diffraction （XRD）, transmission electron microscopy （TEM） with energy dispersive spectrometer （EDS）, Vickers hardness tester and corrosion resistance tester were employed to characterize microstructures and evaluate properties of this coating. According to the results of SEM, XRD and TEM, the cladding coating consisted of nanocrystalline embedded in amorphous phase. EDS data indicated that Nb segregated in the amorphous matrix. The results of hardness test revealed that the hardness of the top layer was higher than that of the inner layer of the coating. The coating exhibited excellent corrosion resistance in a 3.5% NaCl solution.

Microstructure and wear resistance of AlCrFeNiMo_(0.5)Si_(x) high-entropy alloy coatings prepared by laser cladding

In recent years,the coating prepared by laser cladding has attracted much attention in the field of wear research.In this work,AlCrFeNiMo_(0.5)Si_(x)(x=0,0.5,1.0,1.5,2.0)high-entropy alloy coatings were designed and prepared on Q235 steel by laser cladding.The effect of Si content on microstructure,microhardness and wear resistance of the coatings was studied in detail.The results indicate that the AlCrFeNiMo_(0.5)Si_(x) highentropy alloy coatings show an excellent bonding between substrate and the cladding layer.The AlCrFeNiMo_(0.5)Si_(x) coatings are composed of nano-precipitated phase with BCC structure and matrix with ordered B2 structure.With the addition of Si,the white phase(Cr,Mo)_(3)Si with cubic structure appears in the interdendritic,and the morphology of the coating(x=2.0)transforms into lamellar eutectic-like structures.The addition of Si enhances the microhardness and significantly improves the wear resistance of the coatings.As x increases from 0 to 2.0,the average hardness of the cladding zone increases from 632 HV to 835 HV,and the wear rate decreases from 1.64×10^(-5) mm^(3)·(N·m)^(-1) to 5.13×10^(-6) mm^(3)·(N·m)^(-1).When x≥1.5,the decreasing trend of the wear rate gradually slows down.The wear rates of Si1.5 and Si2.0 coatings are 5.85×10^(-6) mm^(3)·(N·m)^(-1) and 5.13×10^(-6) mm^(3)·(N·m)^(-1),respectively,which is an order of magnitude lower than that of Q235 steel.

EFFECT OF CeO_2 ON MICROSTRUCTURE AND WEAR RESISTANCE OF LASER REMELTED FeBSi COATING

The hardness and wear resistance of sprayed FeBSi coating after laser remelting were much improved by addition of 8 wt-% CeO_2.Microstructural observation on the FeBSi+CeO_2 coating revealed that the formation of martensite occurs,as well as the refined grains and the more eutectic and compounds with regular morphology are dis- tributed.While the FeBSi coating free from CeO_2 is a sharp constrast in microstructure.

Effect of process parameters on the microstructure and properties of laser-clad FeNiCoCrTi0.5 high-entropy alloy coating

FeNiCoCrTi0.5 coatings with different process parameters were fabricated by laser cladding. The macro-morphology, phase, microstructure, hardness, and wear resistance of each coating were studied. The smoothness and dilution rate of the FeNiCoCrTi0.5 coating generally increased with the increase of specific energy(Es), which is the laser irradiation energy received by a unit area. FeNiCoCrTi0.5 coatings at different parameters had bcc, fcc, and Ti-rich phases as well as equiaxed, dendritic, and columnar structures. When Es increased, the size of each structure increased and the distribution area of the columnar and dendritic structures changed. The prepared FeNiCoCrTi0.5 coating with the Es of 72.22 J·mm-2 had the highest hardness and the best wear resistance, the highest hardness of the coating reached HV 498.37, which is twice the substrate hardness. The average hardness of the FeNiCoCrTi0.5 coating with the Es of 72.22 J·mm-2 was 15.8% higher than the lowest average hardness of the coating with the Es of 108.33 J·mm-2. The worn surface morphologies indicate that the FeNiCoCrTi0.5 coatings exhibited abrasive wear.

Effect of Fe content on microstructure and mechanical properties of Cu-Fe-based composite coatings by laser induction hybrid rapid cladding

To select the proper composition and obtain an overall material?microstructure?property relationship for Cu?Fe alloy, theeffect of Fe content on microstructure and properties of Cu?Fe-based composite coatings by laser induction hybrid rapid claddingwas investigated. Microstructure characterization of the composite coatings was tested utilizing SEM, XRD and EDS. Microhardnessmeasurement was executed to evaluate the mechanical properties of the composite coatings. The results show that for low Fe content,the composite coating presents a feature that Fe-rich equiaxed dendrites are embedded in the Cu-rich matrix. With increasing Fecontent, the Fe-rich particles are dispersed in the Cu-rich matrix. With further increasing Fe content, large amounts of Cu-richparticles are homogeneously dispersed in the interdendrite of the Fe-rich matrix. Correspondingly, the average microhardness of thecomposite coatings increases gradually with the increase of Fe content and the microhardness of Cu14.5Fe83Si2C0.5 coating is muchtwice higher than that of the substrate.

Influence of Laser Coating on Microstructure and Properties of an Al-Si Alloy

The microstructure and wear resistance of a cast Al-Si alloy coated with metal and rare earth elements and treated by the laser rapid melt-solidification(LRMS)are studied in the pres- ent work.Optical and SEM micrographic analyses showed that a superfine microstructure was ob- tained,and the hardness was remarkably enhanced by the LRMS treatment.Wear test showed that the rapid melt-solidified microstructure had higher wear resistance than that treated by ordinary solid solution treatment.

Microstructure and Sliding Wear Property of Laser Clad TiN－Reinforced Composite Coating

The microstructure and sliding wear property of laser clad TiN-composite coating on steel 1045 were analyzed by SEM, EPMA, XRD, EDAX techniques and a pin-on-ring dry sliding wear testing machine. An excellent fusion bonding with low dilution and absence of cracks was obtained under the laser cladding conditions of specific energy and power density in the range 5 to 20kJ/cm￣2 and 3.5 to 5kW/cm￣2 respectively. The clad layers have been characterized by metallurgical examination. The bonding zone about 6μm thick is analyzed to be γ-Ni solid solution growing from the bottom of molten pool in the form of planar crystal morphology. γ-Ni, TiN particles and fine eutectic of γ-Ni+(Fe, Cr)_(23)C_6, in the interdendritic regions are observed. A large number of TiN particles in irregular shapes are remained afer laser cladding. Partial dissolution appearing on the edges of original TiN particulates and their growth during resolidification are found in the clad region. The TiN-reinforced composite coating produced by laser cladding possesses a good wear resistance n this study. An adhesive wear with a regular scale-like feature on the worn surface was observed.

Microstructure and Wear Resistance Properties of FeCrAl-Cu(Ni,Co)HEA Coatings Synthesized by Laser Remelting

FeCrAlCu,FeCrAlCuNi,FeCrAlCuCo,and FeCrAlCuNiCo high-entropy alloy(HEA)coatings were synthesized on the surface of 45#steel through cold spraying-assisted laser remelting.Results reveal that all four HEA coatings are composed of face-centered cubic+body-centered cubic phases.Additionally,the microstructure of the coatings consists of columnar dendrites.With the simultaneous addition of both Ni and Co elements,the columnar dendritic grains are gradually refined in the coating.Moreover,the FeCrAlCuNiCo HEA coating exhibits excellent friction performance with the coating hardness of 5847.7 MPa,friction factor of 0.45,and wear rate of 3.72×10^(−5) mm^(3)·N^(−1)·m^(−1).The predominant wear mechanism is the adhesive wear and abrasive wear.

Strengthening behavior of AlCoCrFeNi(TiN)_(x) high-entropy alloy coatings fabricated by plasma spraying and laser remelting

High-entropy alloy(HEA)coatings are of great importance in the fabrication of wear resistance materials.HEA coatings containing ceramic particles as reinforcement phase usually have better wear performance.In this study,AlCoCrFe Ni(TiN)_(x)(x:molar ratio;x=0,0.2,0.4,0.6,0.8,1.0)HEA coatings were fabricated on Q235 steel by plasma spray first and then subjected to laser remelting.The experimental results confirm that plasma spray together with post laser remelting could result in the in-situ formation of TiN-Al_(2)O_(3) ceramic particles and cuboidal B2 phase in the AlCoCrFeNi(TiN)_(x) HEA coatings.The in-situ TiN-Al_(2)O_(3) and nano-cuboidal B2 precipitation phase strengthened the coatings and improved their wearresistance properties.Due to the dispersion of hard phase and nano-particles resulting from second heating,the microhardness of the Al Co Cr Fe Ni(Ti N)coatings significantly increased from 493 to 851 HV after laser remelting.For the same reasons,the wear-resistance performance was also significantly promoted after laser remelting.

Anomalous microstructure and tribological evaluation of AlCrFeNiW_(0.2)Ti_(0.5)high-entropy alloy coating manufactured by laser cladding in seawater

To evaluate the potential of high entropy alloys for marine applications,a new high entropy alloy coating of AlCrFeNiW_(0.2)Ti_(0.5)was designed and produced on Q235 steel via laser cladding.The microstructure,microhardness and tribological performances sliding against YG6 cemented carbide,GCr15 steel and Si_(3)N_(4)ceramic in seawater were studied in detail.The AlCrFeNiW_(0.2)Ti_(0.5)coating showed an anomalous’sunflower-like’morphology and consisted of BCC and ordered B2 phases.The microhardness was approximately 692.5 HV,which was 5 times higher than substrate.The coating showed more excellent tribological performances than Q235 steel and SUS304,a typical material used in seawater environment,sliding against all three coupled balls in seawater.Besides,the wear and friction of AlCrFeNiW_(0.2)Ti_(0.5)coating sliding against YG6 in seawater were most mild.The main reason was the generation of Mg(OH)_(2),CaCO_(3),metal oxides and hydroxides and the formation of protective tribo-film on the worn surface of AlCrFeNiW_(0.2)Ti_(0.5)coating in the process of reciprocated sliding.This would effectively hinder the direct contact between the worn surfaces of AlCrFeNiW_(0.2)Ti_(0.5)coating and YG6 ball,resulting in a decrease of friction coefficient and wear rate.Thus the YG6 was an ideal coupled material for AlCrFeNiW_(0.2)Ti_(0.5)coating in seawater,and the coating would become a promising wear-resisting material in ocean environment.

Refined microstructure and enhanced mechanical properties of AlCrFe_(2)Ni_(2) medium entropy alloy produced via laser remelting

A Co-free as-cast AlCrAlCrFe_(2)Ni_(2)medium entropy alloy(MEA)with multi-phases was remelted by fiber laser in this study.The effect of laser remelting on the microstructure,phase distribution and mechanical properties was investigated by characterizing the as-cast and the remelted AlCrAlCrFe_(2)Ni_(2)alloy.The laser remelting process resulted in a significant decrease of grain size from about 780μm to 58.89μm(longitudinal section)and 15.87μm(transverse section)and an increase of hardness from 4.72±0.293 GPa to 6.40±0.147 GPa(longitudinal section)and 7.55±0.360 GPa(transverse section).It was also found that the long side plate-like microstructure composed of FCC phase,ordered B2 phase and disordered BCC phase in the as-cast alloy was transformed into nano-size weave-like microstructure consisting of alternating ordered B2 and disordered BCC phases.The mechanical properties were evaluated by the derived stressstrain relationship obtained from nano-indentation tests data.The results showed that the yield stress increased from 661.9 MPa to 1347.6 MPa(longitudinal section)and 1647.2 MPa(transverse section)after remelting.The individual contribution of four potential strengthening mechanisms to the yield strength of the remelted alloy was quantitatively evaluated,including grain boundary strengthening,dislocation strengthening,solid solution strengthening and precipitation strengthening.The calculation results indicated that dislocation and precipitation are dominant strengthening mechanisms in the laser remelted MEA.

Microstructural evolution and hardness of as-cast Be-Al-Sc-Zr alloy processed by laser surface remelting

As-cast beryllium-aluminum(Be-Al)alloy exhibits a coarse microstructure with pore defects due to a large solidification interval,greatly limiting its mechanical properties.In this research,the relationship between laser surface remelting process and microstructure and hardness of as-cast Be-Al-Sc-Zr alloy was established.The experimental results demonstrated that a pore-free refined microstructure of remelted layer was obtained by controlling the parameter of effective laser energy input.The microstructure of as-cast Be-Al-Sc-Zr alloy consisted of equiaxed grains with Al phase forming a continuous frame wrapping Be phase,which was significantly refined in the remelted zone(from 25μm to 2μm).The Vickers hardness in the remelted zone(approximately 210 HV)was approximately 3 times that of as-cast Be-Al-Sc-Zr alloy.Analysis of the Vickers hardness and the Be phase size showed a good agreement with a Hall-Petch equation.In addition,transmission electron microscopy(TEM),auger electron spectroscopy(AES)and X-ray diffraction(XRD)analysis evidenced that Sc and Zr elements formed a single blocky phase Be13(Scx,Zr1-x),which was also greatly refined from 8μm to 1.5μm in the remelted zone.The results obtained in this study indicate that the laser surface remelting allowed refining the microstructure and further strengthening the Vickers hardness of Be-Al-Sc-Zr alloy.

Laser Surface Remelting of Fe-based Alloy Coating Deposited by APS

The Fe-based amorphous alloy coatings with different porosities were deposited on Q235 steel substrates by means of atmospheric plasma spraying(APS).The as-sprayed coatings were remelted by the facility of a Nd:YAG laser to further enhance their compactness and bonding strength via orthogonal experiment design.The effects of laser remelting on the microstructure,phase compositions and mechanical properties of the as-sprayed coatings were investigated by optical microscopy,scanning electron microscope,X-ray diffraction and Vickers microhardness tester.The corrosion performance of the coatings was evaluated by both potential dynamic measurements(PDM)and electrochemical impedance spectroscopy(EIS)in a 10%NaOH solution.The results indicate that laser power of 700 W,scanning velocity of 4 mm/s,beam size of 3 mm and porosity of 1.19%are the optimized remelting process parameters.The laser-remelted coatings exhibite more homogenous structure as strong metallurgical bonding to substrates.The amorphous phases in the as-sprayed coatings crystallize toα-Fe,Fe2Si,Fe3.5B,and Fe2W phases for the high temperature and rapid solidification in the remelting process.The microhardness values of as-sprayed are in the range of 700-800 HV0.1,while the microhardness values of the remelted coatings are enhanced slightly to 750-850 HV0.1.Both PDM and EIS analysis results show that the remelted coatings exhibite relatively excellent corrosion resistance compared with the stainless steel 1Cr18Ni9Ti,however the corrosion resistance of the remelted coatings is inferior to the as-sprayed amorphous coatings.

Influence of laser surface remelting on microstructure and degradation mechanism in simulated body fluid of Zn-0.5Zr alloy

In this study,the Zn-0.5 wt%Zr(Zn-Zr)alloy was treated by laser surface remelting(LSR),and then the microstructure and degradation mechanism of the remelting layer were investigated and compared with the original as-cast alloy.The results reveal that after LSR,the bulky Zn(22)Zr phase in the original Zn-Zr alloy is dissolved and the coarse equiaxed grains transform into fine dendrites with a secondary dendrite arm space of about 100 nm.During the degradation process in simulated body fluid(SBF),the corrosion products usually concentrate at some certain areas in the original alloy,while the corrosion products distribute uniformly and loosely in the LSR-treated surface.After removing the corrosion products,it was found that the former suffers obvious pitting corrosion and then localized corrosion.The proposed mechanism is that corrosion initiates at grain boundaries and develops into the depth at some locations,and then leads to localized corrosion.For the LSR-treated sample,corrosion initiates at some active sites and propagates in all directions,corrosion takes place in the whole surface with distinctly uniform thickness reduction,while the localized corrosion and peeling of bulky Zn(22)Zr particles were eliminated.The electrochemical results also suggest the uniform corrosion of LSR-treated sample and localized corrosion of original sample.Based on the results,a new approach to regulate the corrosion mode of the biodegradable Zn alloy is proposed.

Synthesis of Titanium Carbide Particle in Laser Melted-pool in situ

The titanium carbide phase was synthesized in laser melted-pool in situ as the reinforced particles of nickel based composite coating on Ti-6Al-4V alloy surface using the nickel and graphite blending powder by laser cladding. The microstructure investigation showed that the petals-shaped particles and granular particles were two main morphology of titanium carbide particles. And a few spiral-shaped titanium carbide pattern and eutectic titanium carbide appeared on the cross-sections of the coating. The spiral-shaped titanium carbide pattern composed of some slender arc-shape titanium carbide particles and the eutectic titanium carbide was fine. The morphology and distribution of the spiral-shaped titanium carbide patterns and eutectic titanium carbide confirmed that their growth mechanism was the dissolution-precipitation mechanism and was affected by the convection behavior of the laser melted pool. The spiral-shaped titanium carbide pattern would precipitate out the high-temperature melts under high-speed convection. The eutectic titanium carbide would precipitate out when the melts stopped convection or dropped to eutectic temperature.

激光熔覆功率对FeCrNiCoMoBSi高熵合金涂层电化学腐蚀性能的影响

探讨了FeCrNiCoMoBSi高熵合金(HEA)激光熔覆涂层的微观结构以及激光功率对涂层物相和电化学腐蚀性能的影响。研究结果显示,HEA涂层由底部的柱状晶带、顶部的等轴晶带以及中间混晶带(由柱状晶和等轴晶混合组成)构成。采用3 000W功率制备的HEA涂层表现出最低的自腐蚀电流密度(0.425μA/cm^(2))、最高的自腐蚀电位(-0.16852V)以及最大的极化阻抗(69 616Ω),其阻抗模值■为1 143Ω·cm^(2),分别是1 800,2 500和4 500 W功率激光熔覆涂层的8.65倍、4.91倍和7.14倍,且其最大相位角为76.23°,均高于其它三种涂层。综合评估显示,采用3 000 W功率制备的HEA涂层具有出色的电化学腐蚀性能。这是由于其单一的FCC晶体结构、抗腐蚀的铁镍合金相和单质铬相、良好的晶体结晶度、细化的晶粒尺寸以及卓越的钝化效应,使其电化学腐蚀性能显著优于其他功率制备的涂层。

背面焊缝激光重熔处理对Ti/Al高速FA-MIG焊接头组织性能的影响

针对钛/铝单面高速超威弧熔化极氩弧焊(FA-MIG)熔钎焊界面组织性能差异大的问题,采用激光对TC4钛/5A06铝FA-MIG焊接头的背面焊缝进行重熔处理,以改善Ti/Al界面显微组织的差异性,提高接头的力学性能。通过不同工艺下接头组织性能的对比分析,研究激光向铝侧偏移量d、激光功率q和焊接速率v对接头组织性能的影响。结果表明,d、q和v对接头组织性能具有重要影响;在d=2 mm,q=1.3 kW,v=5 mm·s^(-1)条件下,经重熔处理的接头根部TiAl3界面反应层明显增厚,接头厚度方向Ti/Al界面显微组织差异明显降低;接头抗拉强度超过280 MPa,比未经处理的接头提高了约20%;拉伸断口呈塑性+脆性混合型断裂。

激光表面重熔对CoCrFeNiW_(0.5)高熵合金组织及性能的影响

采用真空氩弧熔炼制备了非等原子比CoCrFeNiW_(0.5)高熵合金并进行了激光表面重熔处理,系统研究了激光表面重熔对合金相组成、显微组织、硬度及摩擦磨损性能的影响。结果表明:铸态高熵合金的显微组织由枝晶FCC相及枝晶间(FCC+μ)共晶组织组成,激光重熔后合金的共晶组织消失并且晶粒明显细化,金属间化合物μ相以颗粒状分布在等轴FCC的晶界上。与铸态合金相比,激光重熔后合金的硬度提升约17%,与Si_(3)N_(4)陶瓷配副时的摩擦系数降低约7%,磨损率降低约75%,这主要归因于激光重熔过程引起的细晶强化、固溶强化,以及合金组织成分均匀性的提升。

激光重熔对等离子喷涂AlCoCrFeNi高熵合金涂层组织和耐腐蚀性能的影响

现有关于高熵合金涂层重熔处理的研究大多集中在涂层的组织结构、力学性能和耐磨损性能等方面,对其耐腐蚀性能的研究较少。为了揭示激光重熔对高熵合金涂层耐腐蚀性能的影响,采用等离子喷涂技术在AISI 1045钢表面制备AlCoCrFeNi高熵合金涂层,并采用激光重熔工艺对其进行重熔处理,对重熔前后涂层的组织结构和耐腐蚀性能进行对比研究。结果表明:激光重熔基本消除了喷涂层中的孔隙和裂纹等缺陷,涂层与基体之间由机械结合转变为冶金结合;重熔层由BCC固溶体相和少量FCC析出相组成,组织形态呈树枝晶状。极化曲线和电化学阻抗谱分析表明,激光重熔可以改善AlCoCrFeNi高熵合金涂层在3.5%NaCl溶液中的耐腐蚀性能。激光重熔后,涂层的自腐蚀电位从-0.421 6 V增加到-0.282 1 V,腐蚀电流密度从4.809×10^(-7)A/cm^(2)降低到1.475×10^(-7)A/cm^(2)。长期浸泡腐蚀试验也表明重熔层的耐腐蚀性能要显著优于喷涂层。通过等离子喷涂结合激光重熔技术得到缺陷较少、耐腐蚀性较好的高熵合金涂层,对于高熵合金的广泛应用具有重要的参考价值。

Mo含量对激光熔覆CoCrFeNiW_(0.6)Mo_(x)高熵合金涂层组织与性能的影响

目的研究Mo含量的变化对激光熔覆CoCrFeNiW_(0.6)高熵合金涂层的影响。方法使用RFL-C1000光纤激光器,在45钢基体表面制备CoCrFeNiW_(0.6)Mo_(x)(x=0,0.2,0.4,0.6,0.8)高熵合金涂层,并利用Leica DVM6光学显微镜、扫描电镜(SEM)、X射线衍射仪(XRD)、能谱仪、显微硬度仪、电化学工作站对熔覆层的宏观形貌与稀释率、相结构、微观组织结构、硬度、耐腐蚀性能进行测试与分析。结果加入Mo元素后,结合状态与表面形貌良好,当x=0~0.4时,涂层微观组织主要呈树枝晶形态,且晶粒逐渐变细。当x≥0.6时,涂层表面开始有裂纹产生。随着Mo元素的添加,涂层逐渐析出σ相,晶粒尺寸逐渐减小。当x=0.8时,有共晶组织形成。涂层显微硬度随Mo元素的增加而增加,但由于x=0.8时出现较多裂纹,裂纹的出现影响了涂层硬度,导致x=0.8时的硬度减小。当x=0.6时,涂层平均显微硬度最高,达到了959.69HV0.3,约为CoCrFeNiW_(0.6)涂层平均硬度的20.32%。当x=0~0.6时,涂层耐腐蚀性能随着Mo元素含量的增加逐渐提升。当x=0.8时,耐腐蚀性能变差,其原因是裂纹的出现以及σ相的形成使得涂层耐腐蚀性变差。在x=0.6时,涂层耐腐蚀性能最好。结论Mo元素的加入使得涂层微观组织出现σ相,同时有细化晶粒的作用,可以显著改善涂层的硬度以及耐腐蚀性。