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in situ laser deposition of NiTi intermetallics for corrosion improvement of Ti-6Al-4V alloy

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Transactions of Nonferrous Metals Society of China 2015年第10期25卷 3315-3322页

作者： M.N.MOKGALAKA a.p.i.popoola S.L.piTYANA Department of Chemical Metallurgical and Materials EngineeringTshwane University of Technology Council for Scientific and industrial Research National Laser Centre

NiTi intermetallic coatings were fabricated on the surface of Ti-6Al-4V alloy by melting Ni and Ti powders using laser metal deposition（LMD） *** effects of NiTi reinforcement content on the microstructure,hardness and corrosion properties of the coatings were *** results show that the deposited coatings are characterized by NiTi,NiTi2 and NiTi3 intermetallic *** appreciable increase in corrosion resistance is obtained for all the coatings,and Ti55Ni45 coating shows the highest corrosion resistance;while coatings Ti50Ni50 and Ti45Ni55 follow in that *** reinforcement materials are proven to be corrosion resistant in the tested environment,and the effect of Ti is more dominant.

关键词： Ti-6Al-4V alloy NiTi intermetallic laser metal deposition corrosion behaviour

The inhibitive study of egg shell powder on uns n08904 austenitic stainless steel corrosion in chloride solution

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Defence Technology（防务技术） 2018年第5期14卷 463-468页

作者： O.Sanni a.p.i.popoola O.S.i.Fayomi Tshwane University of Technology Department of Chemical Metallurgical and Materials Engineering

The effect of egg shell powder(ES) as an environmental friendly inhibitor was studied for its corrosion inhibitive tendency on N08904 austenitic stainless steel in simulated saline(3.5% NaCl) solution using potentiodynamic polarization, weight loss, and SEM/EDX at room temperature. The experimental data explained the effective performance of ES with values of 57%-100% inhibition efficiency, at 2 g-10 g inhibitor concentration from weight loss tests due to the inhibition of stainless steel. The electrochemical action was as a result of the ionized particles which inhibit the compound influencing the redox reaction mechanism causing surface corrosion. ES's best performance was achieved when 6 g of the inhibitor concentration was added to the saline medium. Corrosion rate value decreased progressively with the presence of inhibitor because of anions adsorption at the interface of the metal film. Corrosion potential(Ecorr) value was found to decrease from-0.3991 V to-0.3447 V in the presence of inhibitor at 2 g concentration, decreasing gradually to-0.2048 at 6 g inhibitor concentration. The compounds identified in the ES completely adsorbed onto the surface of stainless steel as observed from the EDX analysis. The ES adsorption on stainless steel surface obeyed Langmuir adsorption isotherm. A corroded morphology with pits was observed in the SEM results without ES which contrast the images obtained with the presence of ES.

关键词： Austenitic stainless steel Corrosion inhibition Egg shell Chloride Langmuir

influence of spark plasma sintering on microstructure and corrosion behaviour of Ti-6Al-4V alloy reinforced with micron-sized Si_3N_4powder

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Defence Technology（防务技术） 2018年第5期14卷 403-407页

作者： F.M.Kgoete a.p.i.popoola O.S.i.Fayomi Department of Chemical Metallurgical & Materials Engineering Tshwane University of Technology Department of Mechanical Engineering Covenant University

Ti-6 Al-4 V-Si3 N4 composites were effectively fabricated by spark plasma sintering(SpS) technique. The addition of Si_3 N_4 on Ti-6 Ai-4 V was varied from 5% to 15%(wt fraction). The effect of Si_3 N_4 addition on the densification, microstructure, and microhardness and corrosion behaviour of Ti-6 Al-4 V was *** increase in microhardness value was recorded from 325.46 HV_(0.1) to 585.73 HV_(0.1). X-ray diffraction(XRD) analysis showed that the intensity of diffraction peaks of Si3 N4 phase in the composites *** sintered Ti-6 Al-4 V reinforced with Si_3 N_4 compacts revealed the non-existence of intermediate phases, such as TiSi_2(titanium silicide) which was expected. SEM analysis of the spark plasma sintered composites revealed a and β phase microstructures in Ti-6 Al-4 V with uniform distribution of Si3 N4 particulates in the matrix. The corrosion resistance property of the material was improved by the addition of Si_3 N_4 from 0.986629 mm/year to 0.030547 mm/year.

关键词： Spark plasma sintering Si3N4 Ti-6Al-4V Microstructure Corrosion

Characterization of ceramic reinforced titanium matrix composites fabricated by spark plasma sintering for anti-ballistic applications

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Defence Technology（防务技术） 2018年第5期14卷 408-411页

作者： S.W.Maseko a.p.i.popoola O.S.i.Fayomi Department of Chemical Metallurgicaland Materials EngineeringTshwane University of TechnologyPretoriaSouth Africa Department of Mechanical Engineering Covenant UniversityOtaNigeria

Titanium has found extensive use in various engineering applications due to its attractive physical,mechanical, and chemical characteristics. However, titanium has relatively low hardness for use as an armour material. ZrB2 was incorporated to the Ti matrix to form a Ti-based binary composites. in this study, powder metallurgy techniques were employed to disperse the ceramic particulates throughout the matrix material then consolidated through spark plasma sintering. The composites were densified at1300 ℃, pressure of 50 Mpa, and holding time of 5 min. The microstructure and phase analysis of the sintered composites was carried out using SEM and XRD, while the hardness was determined using Vickers' microhardness tester. The SEM and XRD results confirmed the presence of the TiB whiskers which renowned with the improving the hardness of titanium. The hardness of the composite with 10 wt% ZrB_2 showed the highest hardness compared to that obtained for the 5 and 15 wt% ZrB_2 composites which was 495 and 571 Hv respectively.

关键词： SpS TiB whiskers Hardness Titanium matrix composites Reinforcement

Microstructure,hardness and corrosion properties of laser processed Ti6Al4V-based composites

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Transactions of Nonferrous Metals Society of China 2015年第9期25卷 2912-2923页

作者： N.M.BALOYi a.p.i.popoola S.L.piTYANA Department of Chemical Metallurgical and Materials EngineeringTshwane University of Technology Council for Scientific and industrial Research National Laser Center

Nb and Ti-13 Nb powders were used for improving the surface of Ti6Al4 V *** deposition of the powders was carried out at various laser *** scanning electron microscopy（SEM）-EDS and optical microscopy were used for characterization.X-ray diffractometer（XRD） was used for analyzing the elemental composition and phase *** hardness,wear and corrosion properties were *** corrosion and the wear behaviours of the deposited layers were studied in a Hanks solution（simulated body fluid,SBF）.The microstructures of Nb coatings reveal the presence of orthorhombic,dendritic α″ and metastable β-Nb phases which produce uneven hardness with an average of HV *** Ti-13 Nb coatings,martensitic α′ and metastable β-Nb phases with an average hardness of HV 423 were *** resistance of wear on dry sliding of Ti-13 Nb coating is attributed to the increase in *** results indicate that deposition of Nb and Ti-13 Nb on Ti6Al4 V grossly reduces the mass fractions of Al and V in all *** SBF,Nb reinforcement produces the best coating that reveals the best wear and corrosion resistances as compared with the ***,this coating will perform best for orthopaedic implant material enhancement.

关键词： Ti6Al4V-based composite Nb simulated body fluid laser deposition passivation microstructure corrosion property

Effect of Nb addition on the microstructural,mechanical and electrochemical characteristics of AlCrFeNiCu high-entropy alloy

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international Journal of Minerals,Metallurgy and Materials 2020年第10期27卷 1332-1340页

作者： N.Malatji a.p.i.popoola T.Lengopeng S.pityana Tshwane University of Technology PretoriaSouth Africa Council for Scientific and industrial Research PretoriaSouth Africa

AlCrFeNiCuNbx(x=0.05,0.15,and 0.26)high-entropy alloys(HEAs)were successfully fabricated using the laser metal deposition *** laser power of 1600 W and scanning speed of 1.2 m/min were used during laser processing of the *** microstructural,mechanical,and electrochemical characteristics of the alloys were evaluated using various advanced characterization *** showed that the alloys exhibited a dual-phase structure with dendritic *** inclusion of Nb in the AlCrFeNiCu alloy matrix promoted the formation of fine eutectic structures and changed the shape of the grains from columnar to *** Cu content decreased with the increase in the content of Nb,whereas the Al content increased with the increase in the content of *** findings indicated that the presence of Nb in the alloy promoted the formation and enhanced the stability of the body-centered cubic(bcc)*** of the alloys that contained Nb also exhibited high hardness,compressive strength,and wear ***,the low current density and positive shift in potential exhibited by HEAs with appropriate addition of Nb highlighted the superior anticorrosive properties.

关键词： high-entropy alloys microstructure microhardness friction wear loss corrosion resistance

Structural evolution, optoelectrical and corrosion properties of electrodeposited WO_3 integration on Zn-TiO_2 electrolyte for defence super application

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Defence Technology（防务技术） 2018年第5期14卷 396-402页

作者： A.A.Daniyan L.E.Umoru O.S.i.Fayomi a.p.i.popoola Department of Materials Science and Engineering Obafemi Awolowo University Department of Chemical Metallurgical and Materials Engineering Tshwane University of Technology Department of Mechanical Engineering Covenant University

Multifunctional nano composite coatings of Zn-TiO_2-WO_3 were deposited electrolytically on mild steel(MS) from Zn bath, having Zn^(2+) ions and uniform dispersion of TiO_2 and WO_3 nano particulates. The electrical, optical and corrosion resistance characteristics of the electrocodeposited coatings were assessed by Keithley 2400 Series Source meter with Multimeters, Newport Solar Simulator and a pGSTAT30 Autolab potentiostat respectively. The morphological characteristics of the composite coatings were characterized by scanning electron microscope(SEM) equipped with energy dispersive spectrometer(EDS). The result revealed that the electrocodeposits showed good stability and Zn-TiO_2-WO_3 nanocomposite deposits displayed enhanced microstructural qualities, good electrical conductivity and exhibited enriched corrosion resistance.

关键词： Nano-composite Electrocodeposition Corrosion Conductivity and resistance

Electrolytic deposition of super-smart composite coating of Zn-V2O5-NbO2 on low carbon steel for defence application

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Defence Technology（防务技术） 2018年第5期14卷 446-450页

作者： O.S.i.Fayomi L.R.Kanyane a.p.i.popoola S.O.Oyedepo Department of Chemical Metallurgical and Materials EngineeringTshwane University of TechnologyP.M.B.X680PretoriaSouth Africa Department of Mechanical Engineering Covenant UniversityP.M.B 1023OtaNigeria

Despite the massive usages of low carbon steel in automobile for engineering components, its corrosion and high friction coefficient in aggressive environment make it limited in service. This paper is aimed at modifying low carbon steel structural component with thin film composite for enhanced mechanical and corrosion properties. The steel structure was electrodeposited with Zn-V_2 O_5 and embedded with varied NbO_2 weight concentration of 6-12 wt % based electrolyte. Scanning electron microscope(SEM) and high optical microscope was used to study the microstructural evolution of the fabricated coatings. The thermal stability of the fabricated coatings was studied in an isothermal furnace at 300 ℃ and 600 ℃ and further characterized using a high tech optical microscope. potentiodynamic polarization technique was used to investigate the corrosion behavior of the composites in 3.65% NaCl. From the result, the effect of NbO_2 on Zn-V_2 O_5-NbO_2 was massive with improved crystal grain within the coatings lattices. The coating possesses strong metallurgical bonding and good corrosion resistance properties of about 0.315 mm/yr corrosion rate compare to 4.1 mm/yr of as-received sample. No doubt the impact of thermal shock on the resilient characteristics of the composite coating was moderate owing to the stable adherent properties of the deposited coatings.

关键词： Electrodeposition Low carbon steel Micro-hardness Thermal stability corrosion behavior Rare earth metal(REM)

Analysis of inhibition of concrete steel-rebar corrosion by Na_2Cr_2O_7 concentrations:implications for conflicting reports on inhibitor effectiveness

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Journal of Central South University 2013年第12期20卷 3697-3714页

作者： J.O.Okeniyi i.O.Oladele i.J.Ambrose S.O.Okpala O.M.Omoniyi C.A.Loto a.p.i.popoola Mechanical Engineering Department Covenant University Chemical Metallurgical and Materials Engineering Department Tshwane University of Technology

Corrosion test data were measured using non-destructive electrochemical techniques and analysed for studying inhibition effectiveness by different concentrations of NazCr207 on the corrosion of concrete steel-rehar in NaC1 and in H2SO4 media. For these, specifications of ASTM G16-95 R04 were combined with the normal and the Gumbel probability density functions as model analytical methods for addressing issues of conflicting reports of inhibitor effectiveness that had generated concerns. Results show that reinforced concrete samples admixed with concentrations having 4 g （0.012 7 tool）, 8 g （0.025 4 mol） and 6 g （0.019 l tool） NaaCr207 exhibited, in that order, high inhibition effectiveness, with respective efficiency, r/, of （90.46±1.30）%, （88.41＋2.24）% and （84.87±4.74）%, in the NaC1 medium. These exhibit good agreements within replicates and statistical methods for the samples. Also, optimal inhibition effectiveness model in the H2SO4 medium was exhibited by 8 g （0.025 4 mol） Na2Cr207 concentration having r/=（78.44±1.10）%. These bear implications for addressing conflicting test data in the study of effective inhibitors for mitigating steel-rebar corrosion in aggressive environments.

关键词： corrosion inhibitor effectiveness saline/marine and industrial/microbial environments concrete steel-rebar normal andGumbel probability distribution functions Kolmogorov-Smirnov statistics tests of significance