Tin Powder Research Articles

Selective Laser Melting of NiTi Shape Memory Alloy: Processability, Microstructure, and Superelasticity

Nowadays, thanks to the growing interest regarding the manufacturing of 3D complex parts with integrated functionalities, the additive manufacturing of NiTi shape memory alloy is a challenging technological issue. Particularly, 3D printing of NiTi components requires a strong interaction between technological and metallurgical approaches, due to the significant correlation among the process conditions, the microstructure, and the functional performances. The goals of the present work are to define the processability of NiTi powder for realizing fully dense samples using Selective Laser Melting process and the correlation between the microstructure and the superelastic response of specimens processed in different process conditions. It was found that highest relative density values can be obtained for a laser fluence in the range 63–160 J/mm3. The resulting microstructures exhibit variable degrees of orientations, according to the different cooling rates and melt pool size, specific for each condition. Finally, mechanical testing in compression indicated that the as-built alloy exhibits a limited superelastic behavior. A typical flag-like behavior, characterized by 6% of complete recoverable strain, was obtained through heat treatment at 500 °C. This suggests that the microstructure of as-built samples is highly efficient to promote superelasticity after annealing.

ТРИБОЛОГИЧЕСКИЕ ХАРАКТЕРИСТИКИ И ОСОБЕННОСТИ ИЗНАШИВАНИЯ ПОРОШКОВОЙ ОЛОВЯНИСТОЙ БРОНЗЫ С ДОБАВКОЙ УЛЬТРАДИСПЕРСНЫХ ОКСИДОВ

ТРИБОЛОГИЧЕСКИЕ ХАРАКТЕРИСТИКИ И ОСОБЕННОСТИ ИЗНАШИВАНИЯ ПОРОШКОВОЙ ОЛОВЯНИСТОЙ БРОНЗЫ С ДОБАВКОЙ УЛЬТРАДИСПЕРСНЫХ ОКСИДОВ

Wear Behaviors of TiN/WS2 + hBN/NiCrBSi Self-Lubricating Composite Coatings on TC4 Alloy by Laser Cladding

TiN and WS2 + hBN reinforced Ni-based alloy self-lubricating composite coatings were fabricated on TC4 alloy by laser cladding using TiN, NiCrBSi, WS2, and hBN powder mixtures. Energy-dispersive spectroscopy (EDS), scanning electron microscopy (SEM), X-ray diffractometry (XRD), and optical microscopy (OM) were adopted to investigate the microstructure. The wear behaviors of the self-lubricating composite coatings were evaluated under large contact load in room temperature, dry-sliding wear-test conditions. Results indicated that the phases of the coatings mainly include γ-Ni, TiN, TiNi, TiW, WS2, and TiS mixtures. The average microhardness of the composite coating is 2.3–2.7 times that of the TC4 matrix. Laser cladding TiN/WS2 + hBN/NiCrBSi self-lubricating composite coatings revealed a higher wear resistance and lower friction coefficient than those of the TC4 alloy substrate. The friction coefficient (COF) of the coatings was oscillating around approximately 0.3458 due to the addition of self-lubricant WS2 + hBN and hard reinforcement TiN. The wear behaviors testing showed that the wear resistance of the as-received TC4 was significantly improved by a laser cladding TiN/WS2 + hBN/NiCrBSi self-lubricating composite coating.

Comparison study on mechanical properties of powder metallurgy titanium materials with nitrogen solutes and TiN dispersoids

Two types of Ti-based materials with (1) N solutes and (2) TiN particles, as used in powder metallurgy (PM), were prepared from the same pre-mixed pure Ti and TiN powders. An optimized post heat treatment (HT) was applied to the forged samples to completely dissolve the N, originating from TiN particles existing as solid-solution atoms, into the Ti matrix. XRD analysis clearly indicated that only the (0002) α-Ti peak shifted to a lower diffraction angle after HT due to lattice expansion on the c-axis caused by N atoms in solution. Ti-based materials with N solutes showed a large increment in their tensile and compression strengths. Ti composites with TiN dispersoids, however, showed only a very small stress increment. For example, 20 MPa should be the incremental strength rather than the final tensile strength with the addition of 2-mass% TiN particles. Quantitative evaluation of the strengthening mechanism of the Ti-based materials with N solutes using the Hall-Petch equation and the Labusch model revealed that the N solid solution strengthening factor was 90–95% of the total increment in the tensile yield stress. The N solid-solution is thus highly effective in improving the strength of PM Ti materials, relative to Ti composites reinforced with TiN particles.

The Surface Structure of a TiNi-Based Powder Alloy Manufactured by the Method of Diffusion Sintering

The structural features of the surface of a TiNi-based powder alloy produced by diffusion sintering are studied. Two-dimensional porous samples based on a TiNi powder alloy are manufactured for the experimental investigation of their structural features by the methods of non-destructive testing. It is determined that the phase composition of the TiNi-based powder alloy is represented by the TiNi (B2) austenitic phase and precipitates of the secondary phases enriched with nickel – Ti3Ni4 and titanium – Ti2Ni. The chemical compositions of the TiNi compound and the Ti2Ni secondary-phase particles are determined. A three-dimensional reconstruction of the surface of the TiNi-based powder alloy is performed by optical profilometry. It is shown that, depending on the sintering temperature regime and particle size distribution of the TiNi powder, it is possible to obtain a developed rough surface with a roughness coefficient within Ra = 64–87 μm. An analysis of the surface microstructure of the resulting material indicates the existence of several types of terraced relief — hexagonal islands of regular shape 5–10 μm and large terraced structures up to 30– 40 μm in size.

Influence of the Sliding Velocity on the Wear Intensity of the Sintered Hybrid Composite (Al–12Si)–40Sn upon Dry Friction

Tribological tests of a hybrid composite (Al–12Si)–40Sn prepared by sintering mixtures of powders of silumin and pure tin were carried out using the pin-on-disk scheme. It has been established that an increase in the sliding velocity decreases the wear intensity of the composite upon dry friction, while an increase of the load leads to the opposite result. The data obtained indicate that the main contribution to the wear of the composite comes from the delamination of strongly deformed subsurface layers of the material. With an increase in the sliding velocity, the mechanism of the wear does not change, but, because of the heat-induced softening of the material, wear particles of the steel counterbody are pressed into it that “plate” the surface of the sample and reduce its wear intensity.

Superelastic Effect in NiTi Alloys Manufactured Using Electron Beam and Focused Laser Rapid Manufacturing Methods

Two different methods of rapid manufacturing—electron beam additive manufacturing (EBAM) and laser-engineered net shaping (LENS)—were used in order to fabricate NiTi elements. Microstructure and martensitic transformation temperatures of initial materials in the form of wire or spherical powder were established. The samples fabricated using LENS technique showed martensitic transformation temperature (MTT) at − 26 °C (represented by maximum martensite peak maximum in DSC) which was lower in comparison with raw powder. In the case of samples fabricated using EBAM, the MMT reached − 19 °C. The peaks of martensite and reverse transformations were diffuse due to differences in grain size and composition across the sample. Aging at 500 °C for 2 h caused not only separation of R-phase during cooling of both samples, but also formation of sharper and higher transformation peaks as well as shift of MTT to higher temperatures. Microstructural investigation showed columnar grains, near the interface of deposited element and base plate, growing perpendicular to the plate surface. The grains showed axial fiber texture <001> along the growth direction. STEM micrographs revealed the presence of elongated particles enriched in Ti. Formation of Ti-rich particles during the process led to the depletion of Ti in the matrix and contributed to increase in MTT in comparison with initial NiTi powder. LENS-deposited sample additionally contained higher dislocation density in the austenite. Compression stress/strain curves of EBAM-deposited sample revealed deformation of martensite only, while the LENS-deposited one showed almost complete superelastic effect in compression mode up to 3%.

Tribological Characteristics and Wear Features of Powder Tin Bronze with the Addition of Ultrafine Oxides

The effect of the introduction of ultrafine particles of alumina, nickel oxides and a mixture of their oxides on the mechanical and tribological properties, structure and wear characteristics of powder tin bronze is studied. The increase in the content of alumina from 2 to 5 wt % leads to a decrease in strength by 1.2–1.4 times, and from 5 to 10 wt % it does not affect the change in the tensile strength of powder bronze and leads to a slight decrease in the compressive strength. With an increase in the alumina content from 2 to 10%, the coefficient of friction and the wear rate of powder bronze decrease, and the seizure pressure increases. The addition of nickel oxide to alumina promotes the formation of a homogeneous structure, lower porosity and smaller pore size, an increase in strength, a decrease in coefficient of friction of powder bronze from 0.028 to 0.022, by 2.5 times of wear rate, as well as an increase in seizure pressure from 4 to 7.0 MPa.

Исследование свойств износо- и коррозионностойких лазерных покрытий с упрочняющей фазой

One of the most promising methods of spraying protecting coating is the laser coating with strengthening phases, alloying or modifying elements. The purpose of this study is the creation of composite wear and corrosion resistant coatings by additive technology of laser coating for oil and mining industries. The possibility of obtaining complex coating with a strengthening phase is shown. Two variants of coating were considered. Variant 1: support plate made of 12Х18Н10Т stainless steel was cladded with sublayer made of Ni + Cr powder, afterwards the upper cladding layer made of Х23Н5М3ГС steel of Cr-Ni-Мn system was formed with various content of strengthening WC phase in the form of VK-12 powder. Variant 2: support plate made of carbon steel was cladded with four layers of self-fluxing cladding powder PS-12NVK-01 of Ni-Cr-Fe / WC system with addition of nanomodification of powder TiN + Y2O3 + Cr + Fe. The specialists established the dependence of microstructure, structural-phase components and micro hardness of cladded layer from the quantity of WC strengthening phase. The various content of WC strengthening phase (from 10 to 30 %) does not influence the micro hardness of the upper layer significantly – it’s average value is ≈ 700 HV The laser influence on powder mixture leads to partial deterioration of WC strengthening phase, which leads to chemical reaction of tungsten cobalt powder and stainless steеl with formation of complex intermetallic compounds and carbides. Small addition of nanosized modifier TiN + Y2O3 (0,1 % of weight) in a composite mixture with coating power PS-12NVK-01 allows increasing the hardness of protective coating by 1.4, and wear-resistance – by 2 times in comparison to the coatings with similar characteristics, obtained without nanomodifying additions.

Multicomponent bulk metal nitride (Nb1/3Ta1/3Ti1/3)N1−δ synthesis via reaction flash sintering and characterizations

AbstractIn this research, near fully dense single phase bulk multicomponent transition metal nitride (Nb1/3Ta1/3Ti1/3)N1−δ has been successfully synthesized from mixed commercial powders of NbN, TaN and TiN via reaction flash sintering technique. This was performed with an applied pressure of ~ 35 MPa at 25°C under a constant DC electric field (~24‐32 V/cm). The flash event, which is the abrupt increase in current (up to ~ 25.2 A/mm2) and temperature, occurred without preheating. The threshold power dissipation on the sample right before the flash is ~ 0.7 W/mm3. The formation of single phase (Nb1/3Ta1/3Ti1/3)N1−δ random solid solution and its compositional uniformity were confirmed by XRD and EDS, respectively. The effects of ball milling duration and limiting current density on phase formation were studied. Simulation based on Joule heating provides an estimate of the ultimate sample temperature of ~ 1850°C. Vickers hardness of the obtained (Nb1/3Ta1/3Ti1/3)N1−δ is 17.6 ± 0.6 GPa, which is comparable to similarly flash sintered ingredient binary nitrides of TaN and NbN. TGA in air shows that the oxidation resistance of (Nb1/3Ta1/3Ti1/3)N1−δ is better than that of TaN and NbN but inferior to TiN. The study demonstrates that reaction flash sintering can be a highly efficient technique for synthesizing bulk multicomponent ceramics for both material fundamental investigations and application development.

The Surface Morphology of a Ti–6Al–4V Fiber-Lasered Nitride Layer

A fiber laser was used to nitride Ti–6Al–4V titanium alloy the effect of the process parameters on the surface morphology was studied. The surface chemical composition of the nitride layer and the phase of black powder on the surface were analyzed, the two-dimensional and three-dimensional surface topography of the nitride layer surface were measured, and the cross-section microstructure of the nitride layer was photographed. The effects of laser power, laser scanning speed, nozzle distance, and nitrogen flow rate on the surface morphology were studied. The experiments show that the laser power mainly affects the surface oxidation, the laser scanning speed mainly affects the surface roughness, and the nozzle distance has a great influence on the surface morphology. The gas flow rate, however, had a slight effect on the surface morphology. A large heat input and a high nitrogen flow rate caused an increase in TiN and TiO2 black powders. Surface oxidation did not affect the formation of a continuous TiN layer nor surface roughness. Finally, the critical energy density leading to increased surface roughness was calculated.

A structure formation in Ti-Ni powder after high-energy mechanical treatment

In this work a structure formation in Ti-Ni powder after high-energy mechanical treatment in a planetary ball mill with an acceleration of 60g are presented. Mechanical treatment time of powder was 5-300 seconds. It was shown the powder in initial state consists of phase mixture TiN (B2, B19`), Ti2Ni (E93) and TiNi3 (D024). The lattice parameters of powders not significantly change at mechanical treatment and correspond in good agreement with literature data. The quasi-amorphous phase is formed after mechanical treatment and the relative content of phases change so that the relative content of quasi-amorphous phase increases steeply from 0 % to 45 % in first 10 second of treatment mechanical treatment and not significantly changes at more prolong milling. The full widths at half maximum of peaks not significantly change to 10 second mechanical treatment, but the more prolong milling leads to them increasing due to forming of dislocation in all phases, wherein the value of the dislocation density of Ti2Ni phase is more than of TiNi and Ni3Ti phases and corresponds to 1013 cm−2 at 60 second of mechanical treatment.

The Effect of Tungsten Nanoparticles on the Hardness of Sintered Sn-Cu-Co-W Alloys

The effect of tungsten nanoparticles and microparticles on the structure and hardness of sintered Sn–Cu–Co–W alloys has been studied. Tungsten powder of 19–24 μm sized particles was milled in a planetary-centrifugal mill, after which the size of particles was 25 nm to 20 μm. The milled and non-milled tungsten was then mixed with powders of tin, copper and cobalt. The specimens were compacted in moulds and sintered in vacuum at 820°C for 20 minutes. The structure of sintered materials was studied using X-ray diffraction analysis and scanning electron microscopy. Microhardness (HV0.01) of structural constituents and hardness of the materials were measured. It has been determined that it is alloys containing mechanically milled tungsten that have the highest hardness. The main factor influencing the rise of hardness is dispersion hardening with nanoparticles. A further factor is work hardening of tungsten microparticles during ball milling. The highest hardness of 109–111 HRB has been obtained in the Sn–Cu–Co–W alloy containing 23% wt. of milled tungsten, with the proportion of tin, copper and cobalt being 1/2.6/1.6.

The role of graphite addition on spark plasma sintered titanium nitride

Composites of titanium nitride reinforced with graphite were synthesized using spark plasma sintering at 2000°C. The effects of graphite addition on the microstructure, relative density, and mechanical properties of TiN ceramics matrix were examined. The investigation was performed on TiN powder with varying graphite content (1–5wt.%) for 8h using an energy ball milling equipment. Results show that TiN without and with graphite (TiN+1wt.% graphite) sintered at 2000°C recorded sintered relative density of 96.7% and 97% respectively. Additionally, TiN with 3wt.% graphite had a relative density of 98%. However, the shrinkage of TiN+3wt.% graphite was observed to be the lowest compared to other composites at the same sintering conditions. Microstructural analysis indicates that the grain of titanium nitride in the composite was very fine and continuous. Subsequently, a bimodal particle sizes were observed when 5wt.% graphite was dispersed in TiN. The highest Vickers microhardness of 23.5GPa and fracture toughness of 6.5MPam1/2 were achieved with composites reinforced with 3wt.% graphite at milling period of 8h. The combination of TEM/EDS and HRTEM/FFT show a single pattern of diffraction and consistency in interplanar distance obtained from X-ray diffractometry of the milled sample. There is a clear coherence interface between the phases.

Improvement the Strength of a Dental Filling Restoration by Adding of NiTi alloy Powder to Galloy

Gallium has the second lowest melting point of all metals after mercury (29.8 ºC) and has the ability to reactwith metals and alloys at room temperature to produce a workable plastic mass that hardens with time. As aresult Gallium-based alloys have been introduced to the dental market as mercury-free amalgam substitutes.Filling material produced by mixing amalgam alloy powder with gallium liquid instead of mercury. Thiswork involves addition of NiTi alloy powder to Galloy to improve some mechanical properties. Theseproperties included compression, hardness, tensile strength and creep. The characterization of preparedNiTi/Galloy with five wt% of addition (1, 2, 3, 4, and 5 wt%) was done by XRD and SEM/EDS. The resultsshowed that the hardness, compression and diametral tensile strength were increased with increasing wt%of added NiTi alloy powder and the creep percent was decreased where NiTinano powder alloy disperses inthe matrix of the alloy and prevents the dislocation movement, also the NiTi powder particles have uniqueproperties of super elasticity that work to increase the creep strength.

Synthesis of dihydroquinoxalin-2(1H)-ones by tin powder-promoted di- and mono-allylation of quinoxalin-2(1H)-ones

An efficient method of tin powder-promoted di- and mono-allylation of quinoxalin-2(1H)-ones has been developed, which provides a practical route for the synthesis of dihydroquinoxalin-2(1H)-one derivatives in good yields. This protocol uses the combination of allylbromides and tin powder to replace the traditional allylstannanes to make the organotin-participated process less toxic, and has the advantages of readily available starting materials, mild reaction conditions, and a wide scope of substrates.

Aqueous Sn-S Complex Derived Electron Selective Layer for Perovskite Solar Cells

A novel aqueous Sn-S complex solution was applied as precursor to fabricate SnO2 electron selective layers (ESLs) for the hybrid perovskite solar cells (PSCs). The tin and sulfur powder were directly dissolved in a (NH4)2S water solution to form Sn-S precursor. After depositon and annealing, the SnO2 film was formed, presenting as a low cost and enviromental friendly method for preparation of ESL. The films showed excellent transmittance at visible wavelength range. Moreover, the method exhibited high compatibility for doping using Cu, Cd, Li, and Zn elements. Zn doping (0.05 M) in the as-prepared SnO2 ESL significantly improved perovskite solar cells (PSCs) performance. The highest PCE of 13.17% was achived with 15% enhancement compared to that of undoped SnO2 ESL samples. TiCl4 modifications on SnO2 film improved photovoltaic performance to 14.45%, but resulted in the poor long-term stability, around 80% more degredation than that of PSCs based on Zn-doped SnO2 films.

Experimental and Theoretical Study on the False Positive of Monomethyltin Determination in Toys Based on Gastric Juice Migration.

Background Organic tin compounds (OTCs), a group of high-risk hazardous substances, are highly concerned in safety regulation of consumer products especially for toys because they can cause serious damage to organs after prolonged or repeated exposure. Gastric juice migration is nowadays widely implemented to assess organic tin intake from toys or food-contact materials; however, the followed up detection method using sodium tetraethylborate [NaB(Et4)] as a derivatization agent may directly lead to false positive of monomethyltins (MMT). Objective In order to avoid the phenomena of false positive of MMT in the course of laboratory testing of toys, it is necessary and important to perform relative experimental and theoretical studies to reveal the cause of false positive of MMT. Method With metal tin powder as a representative of inorganic tin which existed in real samples, it was treated with artificial gastric juice (0.07 mol/L·HCl), followed by ethyl derivatization using sodium tetraethylborate [NaB(Et)4] and then analyzed by gas chromatography-mass spectrometry (GC-MS) according to the procedure specified in the standard of EN 71-3:2013+A3:2018 issued by the European Committee for Standardization (CEN). Results Without any OTCs in the starting materials, MMT false positive can be reproduced by detecting 0.56 mg/L of triethylmethyltin (TEMT) together with approximately 1000 mg/L of tetraethyltin (TeET), which is similar to real samples. Further, it is demonstrated that the detected amount of TEMT is linearly related with the added amount of NaB(Et)4, and that the formation of TEMT (methyl derivative) is easier than TeET (ethyl derivative) even though the ethyl group is present in a larger amount than the methyl group. Conclusions The phenomena of MMT false positive which occurred in the laboratory testing of toys is mainly because that TEMT is highly likely to be obtained from the reaction of inorganic tin and trace level of methylation agent impurities contained in the derivatization reagent—NaB(Et)4. To avoid MMT false positive, it is concluded that the maximum acceptable mole ratio of methylation agent impurities contained in NaB(Et)4 is approximately 0.028%. This research is helpful to be aware of methylation impurities and is favorable to avoid false judgment caused by MMT false positive in routine analysis of toys.

Thermal analysis and morphology of the ball-milled Ti-Ni powder

The initially spherical titanium (Ti) powder particles were flattened to ‘pan-cake” shape during Ball milling (BM) of the Ti-Ni powder mixture. Ultrafine Ni particles coated the pancakes of Ti particles after the final milling process of 8 h (h). The XRD patterns of the milled TiNi powders did not show obvious alloying. However, analysis of the (1 1 1) planes revealed a slight shifting on peak positioning which is attributable to powder deformation. Thermal analysis of unmilled Ti50Ni powder exposed the Ni Curie point at ∼353 °C. The normal α → β phase transformation in CP Ti was suppressed due to the presence of Ni powder. Differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the milled and annealed powders.

Effect of Vacuum Hot Pressing Temperature on the Mechanical and Tribological Properties of the Fe–Cu–Ni–Sn–VN Composites

The mechanical (hardness and elastic modulus) and tribological (friction force and wear rate) properties of the Fe–Cu–Ni–Sn–VN composites produced by cold pressing and subsequent vacuum hot pressing at different temperatures are studied. The starting iron, copper, nickel, and tin powders have 5–50 μm particles and the vanadium nitride powder has 0.1–0.7 μm particles. When vacuum hot pressing temperature rises from 800 to 1000°C, the hardness increases from 3.75 to 5.37 GPa and the elastic modulus decreases from 176 to 125 GPa. As a result, the friction force reduces from 115 to 80 mN and the wear rate from 1.93 ∙ 10–5 to 0.45 ∙ 10–5 mm3 ∙ N–1 ∙ m–1. The factors promoting improvement of the mechanical and tribological properties of the sintered composites are discussed. In particular, the main factor improving the mechanical properties is that the grains are refined from 5–50 μm to 20–400 nm through the α → γ → α transformation when VN dissolves in α-Fe. In this case, the composite consists of a supersaturated solid solution of nitrogen and vanadium in α-iron, intermetallic Cu9NiSn3, and primary and secondary particulate vanadium nitride phases. A relationship between the structure and mechanical and tribological properties is established. The H/E and H3/E2 parameters that describe the elastic strain resistance and plastic strain resistance correlate with the wear resistance. The sintered composites are regarded as promising materials for developing a new generation of diamond-containing composites for stone processing industry.