Surface modification of 2Cr13 oil pump steel by plasma immersion ion implantation–ion beam enhanced deposition (PIII–IBED)

2Cr13 martensite steel is often used as a piston material in oil pumps. In the harsh environment of an oil field, the materials and components undergo extensive and accelerated wear and tear. In this study, we employ Ti and N plasma immersion ion implantation and ion beam enhanced deposition (PIII-IBED) to enhance the surface wear resistance of 2Cr13 steel in an effort to prolong its working lifetime. To assess the technique efficacy and surface properties of the 2Cr13 steel samples treated by PIII-IBED using different voltages, the coefficient of friction, wear tracks, microhardness, anode polarization curves, chemical composition and elemental depth profiles were determined. The experimental data show that the wear resistance of the treated 2Cr13 steel samples is improved significantly by the method, and the nitride phases formed in the modified layer play an important role in the enhancement mechanism.     

A comparative study of Ni–Ti and Ni–Ti–Cu shape memory alloy processed by plasma melting and injection molding

Shape memory alloys (SMA) are smart materials that present potential applications in such diverse areas as aeronautics, automotive, electronics, biomedicine and others. This work aimed at comparing some physical and functional properties of a Ni–Ti–Cu and equiatomic Ni–Ti SMA. Therefore, Ni–50Ti and Ni–50Ti–5Cu (at.%) were manufactured using plasma melting followed by injection in metallic mold, named Plasma Skull Push–Pull (PSPP) process. Afterwards, samples of both Ni–Ti based SMA were annealed at 1113 K during 2400 s and water quenched. The obtained specimens were analyzed by optical microscopy, microhardness, differential scanning calorimetry, electrical resistance as a function of temperature, and force generation tests. The results showed that Ni–Ti alloy presented higher levels of hardness and lower generated recover forces during heating when compared to the Ni–Ti–Cu SMA. Moreover, the Ni–Ti alloy holds hysteresis larger than the Ni–Ti–Cu SMA as a result of the presence of the R-phase transformation. There was also a better stability under thermal cycling of NiTiCu SMA compared with the equiatomic NiTi.     

Indentation behaviour and wear resistance of pseudoelastic Ti–Ni alloy

Abstract

Recent studies demonstrate that near equiatomic Ti–Ni alloys possess high resistance to surface damage by wear. It is suggested that the high wear resistance of Ti–Ni alloys is closely correlated to their pseudoelasticity, which is usually evaluated by tensile testing. However, when a Ti–Ni alloy is under wear, its surface is in a complex stress state. Since the thermoelastic martensitic transformation of Ti–Ni alloys responds differently to different stresses, it may not be appropriate to evaluate the pseudoelasticity by tensile testing. The present paper reports recent work on pseudoelastic behaviour of a Ti–51 at.-%Ni alloy employing a microindentation technique as well as tensile testing methods. In the present work, the wear performances of Ti–51 at.-%Ni alloy specimens with different degrees of pseudoelasticity were also investigated, and efforts were made to explain the beneficial effect of pseudoelasticity on the wear resistance of Ti–Ni alloys.     

Effects of annealing and deforming temperature on microstructure and deformation characteristics of Ti–Ni–V shape memory alloy

Effects of annealing temperature T_an and deforming temperature T_d on microstructure and deformation characteristics of Ti–50.8Ni–0.5V (atomic fraction, %) shape memory alloy were investigated by means of optical microscopy and tensile test. With increasing T_an, the microstructure of Ti–50.8Ni–0.5V alloy wire changes from fiber style to equiaxed grain, and the recrystallization temperature of the alloy is about 580 °C; the critical stress for stress-induced martensite σ_M of the alloy decreases first and then increases, and the minimum value 382 MPa is got at T_an = 450 °C; the residual strain ?_R first increases, then decreases, and then increases, and its maximum value 2.5% is reached at T_an = 450 °C. With increasing T_d, a transformation from shape memory effect (SME) to superelasticity (SE) occurs in the alloy annealed at different temperatures, and the SME → SE transformation temperature was affected by T_an; the σ_M of the alloy increases linearly; the ?_R of the alloy annealed at 350–600 °C decreases first and then tends to constant, while that of the alloy annealed at 650 °C and 700 °C decreases first and then increases. To get an excellent SE at room temperature for Ti–50.8Ni–0.5V alloy, T_an should be 500–600 °C.     

The effect of indium on porcelain bonding between porcelain and Au−Pd−In alloy

The effect of small In additions on oxide structure and porcelain adherence to Au–Pd alloys was studied. In was oxidized internally as In₂O₃. No uniform external oxide layer could be seen. Small In addition (1 at %) did not have any detectable effect on porcelain adherence (12 MPa), whereas higher In concentration (5 at %) caused significant increase in bond strength (26 MPa). This increase was probably a result of higher In₂O₃ concentration at the surface.     

Wetting and interfacial behavior of Ni–Si alloy on different substrates

Wetting of molten Ni–56 at.% Si alloy on different substrates (SiC ceramic, Ni- and Co-based superalloys, Kovar, and Mo) are performed under different experimental conditions by the sessile drop technique. Temperature, atmosphere, and substrate composition play the key roles in determining the wettability, the spreading characteristics, and the interfacial morphology of the final interfaces. The non-reactive wetting characteristics in Ni–Si/SiC system are confirmed, with a spreading rate increasing with temperature increasing. In the Ni–Si/metal systems the spreading process is determined by the competition between spreading along the substrate surface and the interfacial interactions. Excellent wettability and fast spreading are found in the Ni–Si/Co-based superalloy, Ni–Si/Kovar, and Ni–Si/Mo systems at both the temperatures (1100 and 1200 °C). These results can be used as a reference guide for joining SiC to these metallic components, or to itself, using the Ni–Si alloy as filler metal.     

Electroless deposition of Ni–P–B4C composite coating on AZ91D magnesium alloy and investigation on its wear and corrosion resistance

In the present work, the effect of applying ternary Ni–P–B₄C composite coating from an electroless plating bath containing sulfate nickel, sodium hypophosphate and suspended B₄C particles, on the corrosion and wear resistance of an AZ91D, high aluminum cast magnesium alloy, was investigated. Regarding low corrosion resistance of magnesium alloys, chromium oxide plus HF (Hydro Fluoric Acid) pretreatment was applied to prepare the substrate for coating treatment in electroless bath. The pH value and temperature of the electroless bath were 9 and 82 °C, respectively. The coating was characterized for its micro structure, morphology, microhardness, wear and corrosion resistance. SEM (Scanning Electron Microscope) observation showed dense and coarse nodules in the ternary composite coating and the cross section of Ni–P–B₄C coating offered presence of well dispersed B₄C particles in the coating. The hardness of the Ni–P–B₄C composite coatings was around 1200 MPa, more than what can be obtained for Ni–P coatings (about 700 MPa). The wear test which was carried out by using pin on disc method, showed that ternary Ni–P–B₄C composite coating had a good wear resistance and more superior than Ni-P coating. The polarization test results for ternary Ni–P–B₄C composite coating exhibited good corrosion resistance properties in protecting the AZ91D magnesium alloy, but not better than Ni–P coating.     

Electroless deposition of Ni–W–P–B4C nanocomposite coating on AZ91D magnesium alloy and investigation on its properties

In the present work, electroless deposition of quaternary Ni–W–P–B₄C composite coatings on AZ91D magnesium alloy was investigated. The coatings were characterized to study their microstructure, crystallite size, morphology, microhardness and corrosion resistance and compared with Ni–P and Ni–P–B₄C composite coatings, prepared with the same method. The hardness of the Ni–W–P–B₄C composite coatings was around 1290 MPa which was more than that of the Ni–P and Ni–P–B₄C coatings (about 700 and 1200 MPa, respectively). According to polarization test results, the Ni–W–P–B₄C composite coating exhibits less and more corrosion rates with respect to the Ni–P–B₄C and the Ni–P coatings, respectively. X-ray diffraction (XRD) analysis results for the Ni–W–P–B₄C coating showed that the Ni–W–P–B₄C coating has a combination of amorphous and nanocrystalline structures. Also, Williamson–Hall analysis on the X-ray patterns revealed that the Ni–W–P–B₄C coating has an average crystallite size of 1.5 nm.     

Impaired bacterial attachment to light activated Ni–Ti alloy

Ni–Ti alloy due to its unique mechanical properties, is used for many types of implants. Failure of these implants can be attributed to many different factors; however infections are a common problem. In this paper, the attachment of the bacteria, Staphylococcus aureus, to the Ni–Ti surface modified by a range of processes with and without of light activation (used to elicit antimicrobial properties of materials) was assessed and related to different surface characteristics. Before the light activation the number of bacterial colony forming units was the greatest for the samples thermally oxidised at 600 °C. This sample and the spark oxidised samples showed the highest photocatalytic activity but only the thermally oxidised samples at 600 °C showed a significant drop of S. aureus attachment. The findings in this study indicate that light activation and treating samples at 600 °C is a promising method for Ni–Ti implant applications with inherent antimicrobial properties. Light activation was shown to be an effective way to trigger photocatalytic reactions on samples covered with relatively thick titanium dioxide via accumulation of photons in the surface and a possible increase in defects which may result in free oxygen. Moreover, light activation caused an increase in the total surface energy.     

Cu–Ni alloy electrodeposition on microstructured surfaces

This research experimentally investigated how the solid fraction level of an array of projecting nickel cylindrical microstructures influenced the electrodeposition of Cu–Ni alloy on the cylindrical microstructures. The electrodeposition of Cu–Ni alloy on a substrate with an array of projecting cylindrical structures resulted in the concentrated precipitation of Cu ions at the top of the cylinders. Relatively more electrodeposited structures were formed at the top surface of the cylinders than at the bottom surface, and electrodeposited structures were not formed at the bottom surface of the substrate when the solid fraction was increased. Structures at the edges of the cylinders’ top surfaces grew larger than the structures at the centers of the surfaces. The heights of the electrodeposited structures decreased as the solid fraction increased. In addition, shadow bands with no electrodeposited structures were observed at the bottom surface of the substrate a certain distance away from the cylinders.     

Effect of rare earth elements on plasma electrolytic carbonitriding of Ti–6Al–4V alloy

The paper aims to research the effect of rare earth elements on the carbonitriding layer of titanium alloy by establishing a theoretical model between rare earth concentration and atomic diffusion efficiency. It shows that adding rare earth can not only refine the discharge holes, but also reduce surface cracks, which significantly improve the surface quality of the strengthening layer. It is also found that an appropriate amount of rare earth can greatly increase the growth rate of the carbonitriding layer and carbon content near the surface. Furthermore, compared with the conventional plasma electrolytic carbonitriding treatment, adding 2?g?L^?1 cerium oxide can effectively reduce the activation energy of carbon, so as to improve its diffusion ability.     

A spectroscopic and microstructural study of oxide coatings produced on a Ti–6Al–4V alloy by plasma electrolytic oxidation

In this study, we have used PEO (plasma electrolytic oxidation) for the production of oxide coatings on a Ti–6Al–4V alloy at two different current modes, namely pulsed unipolar and bipolar. Optical emission spectroscopy (OES) in the visible and near UV band (280–800 nm) was used to characterize the PEO plasma. The emission spectra were recorded and the plasma temperature profile versus processing time was constructed using a line intensity ratios method. The aim of this work was to study the effect of the process parameters, including current mode and pulse duration time, on the plasma characteristics, surface morphology and microstructure and corrosion resistance of oxides grown on Ti–6Al–4V by PEO process. Scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDS) and X-ray diffraction (XRD) were used to study the coating microstructure, morphology and phase composition. The corrosion resistance of the coated and uncoated samples was examined by potentiodynamic polarization in a 3.5% NaCl solution. It was found that the plasma temperature profiles are significantly influenced by changing the current mode from unipolar to bipolar. The strongest discharges that are initiated at the interface between the substrate and the coating can be reduced or eliminated by using a bipolar current mode. This produces a thinner, denser and more corrosion-resistant coating.     

Influence of Ni concentration and deposition potential on the characterization of thin electrodeposited Zn–Ni–Co coatings

The electrodeposition of Zn–Ni–Co alloys from sulphate electrolytes was studied on steel rod. In order to elucidate the characteristics of the layer formation, a complementary approach was used based on the combination of various electrochemical techniques. The cyclic voltammetry and galvanostatic techniques for electrodeposition, while potentiodynamic polarization resistance and anodic linear sweeping voltammetry techniques were used for corrosion study. Under the examined conditions, electrochemical and surface analysis indicate that the deposition has taken place with the formation of three structures have a composition corresponding to pure Zn, γ-Ni₅Zn₂₁ and pure Co phases. The influence of nickel concentration as well as the effect of potential on the surface appearance and the deposits composition was examined. Under these experimental conditions the electrodeposition of the alloys is of anomalous type. The results indicate that the addition of Ni to the Zn–Co alloy, Zn–Ni–Co alloy formed which is more corrosion resistance than Zn–Co alloy. Also, the amount of γ-phase increased and the amount of pure Zn decreased with the increase of nickel concentration in the bath. The corrosion resistance of the zinc–nickel–cobalt alloy had been improved with the more concentration of nickel. The Ni content in the deposition layer had been increased at high deposition potential, whereas, pure Zn deposition had been decreased.     

Surface preparation of bioactive Ni–Ti alloy using alkali,thermal treatments and spark oxidation

The primary aim of this study was to compare different surface treatments used for bioactivation of pure titanium surfaces––thermal, alkali treatment and spark oxidation, and to assess their suitability as treatments for Ni–Ti alloys. This was considered by examining the surface properties, calcium phosphate precipitation from a physiological solution, and nickel ion release. Additionally, changes in the transformation temperature were measured for thermally treated samples. These studies indicate that the native surface of Ni–Ti alloy is highly bioactive when assessing the precipitation of calcium phosphates from Hank’s solution. Low temperature heat treatments also produced promising surfaces while high temperature treatment resulted in a very low rate of Ca and P precipitation. Alkali treatment and spark oxidation resulted in some bioactivity. Nickel ion release was greatest for alkali treated and sparks oxidized samples, and the rate of its release from these two samples was on the verge of daily safe dose for adolescent human. The other analyzed samples revealed very low rates of nickel ion release. Heat treatment at 400°C resulted in significant increase in the transformation temperatures, and a further increase of the treatment temperature up to 600°C caused a drop of the transformation temperature.     

Effect of Ta incorporation on the microstructure,electrical and optical properties of Hf1−xTaxO high-k film prepared by dual ion beam sputtering deposition

The microstructure, electrical and optical properties of Hf_1−xTa_xO (x = 0, 0.18, 0.28, 0.36 and 0.43) high-k thin films deposited by a novel deposition technique—dual ion beam sputtering deposition (DIBSD) have been investigated. From the O1s and Si 2p spectra of X-ray photoelectron spectroscopy (XPS), it is worth noting that the thickness of the interfacial layer significantly decreases after doping appropriate content Ta, and the formation of metal silicate components (M–O–Si) can be effectively suppressed by doping 43% Ta concentration into Hf_1−xTa_xO system. Compared to the pure HfO₂ sample, Hf_1−xTa_xO with 43% Ta after post-deposition annealing (PDA) exhibits the highest k-value (∼21.0 ± 0.2) and crystallization temperature (950 °C), the smallest root mean square (RMS) surface roughness of R_a ∼ 0.12 nm, Max height–depth R_p−v ∼ 1.5 nm and C–V hysteresis of 50 mV, the lowest leakage current density of 1.13 × 10⁻⁸ A/cm² at V_g=(V_fb−1) and an acceptable value of E_g ∼ 4.68 ± 0.1 eV.     

Evolution behavior of δ phase in Cu12Sn2Ni alloy and the corresponding effects on alloy property

With the increase of tin content in tin bronze, the rise of δ phase made the strength, hardness of tin bronze increase and the ductility decrease sharply, that difficult to process. In this paper, the Cu12Sn2Ni alloy was prepared by centrifugal casting, the microstructure and phase formation before and after heat treatment were observed by x-ray diffraction, scanning electron microscope, and transmission electron microscope. The results showed that the as-cast sample microstructure was composed of equiaxed grains rather than coarse dendrites. centrifugal casting inhibits tin diffusion to form metastable phase β′-Cu_13.7Sn. The as-cast sample had good deformability and its tensile strength and elongation were 381.9 MPa and 12.4 %, respectively, which are higher than the mechanical properties of gravity casting. The tensile strength and elongation of the sample after furnace cooling at 620 °C/8 min are 439.5 MPa and 24.4 %, respectively, the increase was 16.6 % and 85.07 %, compared with the as-cast samples, due to the solid solution strengthening, the second phase strengthening and the homogenization of the microstructure.     

Fretting wear study of surface modified Ni–Ti shape memory alloy

A combination of shape memory characteristics, pseudoelasticity, and good damping properties make near-equiatomic nickel–titanium (Ni–Ti) alloy a desirable candidate material for certain biomedical device applications. The alloy has moderately good wear resistance, however, further improvements in this regard would be beneficial from the perspective of reducing wear debris generation, improving biocompatibility, and preventing failure during service. Fretting wear tests of Ni–Ti in both austenitic and martensitic microstructural conditions were performed with the goal of simulating wear which medical devices such as stents may experience during surgical implantation or service. The tests were performed using a stainless steel stylus counter-wearing surface under dry conditions and also with artificial plasma containing 80 g/L albumen protein as lubricant. Additionally, the research explores the feasibility of surface modification by sequential ion implantation with argon and oxygen to enhance the wear characteristics of the Ni–Ti alloy. Each of these implantations was performed to a dose of 3 × 10¹⁷ atom/cm² and an energy of 50 kV, using the plasma source ion implantation process. Improvements in wear resistance were observed for the austenitic samples implanted with argon and oxygen. Ion implantation with argon also reduced the surface Ni content with respect to Ti due to differential sputtering rates of the two elements, an effect that points toward improved biocompatibility.