Mechanical properties and wear and corrosion resistance of electrodeposited Ni-Co/SiC nanocomposite coating

Ni-Co/SiC nanocomposite coatings with various contents of SiC nano-particulates were prepared by electrodeposition in a Ni-Co plating bath containing SiC nano-particulates to be co-deposited. The influences of the nanoparticulates concentration, current density, stirring rate and temperature of the plating bath on the composition of the coatings were investigated. The shape and size of the SiC nano-particulates were observed and determined using a transmission electron microscope. The polarization behavior of the composite plating bath was examined on a PAR-273A potentiostat/galvanostat device. The wear behavior of the Ni-Co/SiC nanocomposite coatings was evaluated on a ball-on-disk UMT-2MT test rig. The worn surface morphologies of the Ni-Co/SiC nanocomposite coatings were observed using a scanning electron microscope. The corrosion behavior of the nanocomposite coatings was evaluated by charting the Tafel curves of the solution of 0.5 mol L⁻¹ NaCl at room temperature. It was found that the cathodic polarization potential of the composite electrolyte increased with increasing SiC concentration in the plating bath. The microhardness and wear and corrosion resistance of the nanocomposite coatings also increased with increasing content of the nano-SiC in the plating bath, and the morphologies of the nanocomposite coatings varied with varying SiC concentration in the plating bath as well. Moreover, the co-deposited SiC nano-particulates were uniformly distributed in the Ni-Co matrix and contributed to greatly increase the microhardness and wear resistance of the Ni-Co alloy coating.     

Studies on wettability, mechanical and tribological properties of the polyurethane composites filled with talc

A series of polyurethane (PU)/talc composites modified by a high molecular weight hydroxyl-terminated polydimethylsiloxane (HTPDMS) were prepared. The effect of the talc content on the mechanical, wettability and tribological properties of the PU composites was studied. Tensile strength of the PU composites reached to the maximum after adding 5% talc. The water contact angles (CA) of the original surfaces and worn surfaces of the polyurethane composites were measured. The experimental results indicated that the contact angles of the worn surface increased after friction. The friction and wear experiments were tested on a MRH-3 model ring-on-block test rig at different sliding speeds and loads under dry sliding and water lubrication. Experimental results revealed that the talc contributed to largely improve the tribological properties of the PU composites. The coefficient of friction (COF) of the composites increased with increasing talc. Scanning electron microscopic (SEM) investigations showed that the worn surfaces of the talc filled PU composites were smoother than pure polyurethane under given load and sliding speed.     

Comparison of tribological properties of CrN, TiCN and TiAlN coatings sliding against SiC balls in water

CrN, TiCN and TiAlN coatings were deposited on WC cemented carbide disks using enhanced cathodic arc magnetron sputtering and their topographies and structures were observed and analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The friction and wear properties of CrN, TiCN and TiAlN coatings sliding against SiC balls in water were investigated and compared synthetically using ball-on-disk tribometer. The results showed that the CrN/SiC tribopairs showed the lowest friction coefficient of 0.076, while the TiCN/SiC tribopairs displayed the highest friction coefficient of 0.264. For the CrN/SiC tribopairs the specific wear rate of CrN coatings was lowest while that of SiC balls became highest. But for the TiAlN(TiCN)/SiC tribopairs, the specific wear rate of TiAlN coatings was highest while that of SiC balls for the TiCN/SiC tribopairs became lowest. This indicated that the friction and wear behaviors of nitride coatings/SiC balls tribo-systems in water were more strongly influenced by the anti-oxidative ability of tribomaterials in water than by their mechanical properties.     

Influence of nitrogen ion implantation fluences on surface structure and tribological properties of SiC ceramics in water-lubrication

Nitrogen ions were implanted into SiC ceramics by using ion implantation technology (N⁺-SiC). The surface structure and chemical bonds of N⁺-SiC ceramics were determined by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and their nanohardness was measured by nanoindenter. The friction and wear properties of the N⁺-SiC/SiC tribo-pairs were investigated and compared with those of SiC/SiC tribo-pairs in water using ball-on-disk tribo-meters. The wear tracks on the N⁺-SiC ceramics were observed by non-contact surface profilometer and scanning electron microscope (SEM) and their wear volumes were determined by non-contact surface profilometer. The results show that the N⁺-SiC ceramics were mainly composed of SiC and SiCN phase and SiN, CC, CN and CN bonds were formed in the implantation layer. The highest hardness of 22.3 GPa was obtained as the N⁺-SiC ceramics implanted at 50 keV and 1 × 10¹⁷ ions/cm². With an increase in nitrogen ion fluence, the running-in period of N⁺-SiC/SiC tribo-pairs decreased, and the mean stable friction coefficient decreased from 0.049 to 0.024. The N⁺-SiC ceramics implanted at 50 keV and 5 × 10¹⁷ ions/cm² exhibited the excellent tribological properties in water. In comparison of SiC/SiC ceramic tribo-pairs, the lower friction coefficient and lower wear rate for the N⁺-SiC/SiC tribo-pairs were acquired.     

Microstructure and tribological behaviors of Ti6Al4V alloy treated by plasma Ni alloying

Ni modified layer was prepared on surface of the Ti6Al4V substrate by plasma surface alloying technique. Surface morphology, micro-structure, composition distribution, phase structure, and microhardness of the Ni modified layer were analyzed. Tribological performance of the Ni modified layer and Ti6Al4V substrate was investigated by using pin-on-disc tribometer. The results indicate that roughness of the Ni modified layer was increased due to formation of the micro-convex on the modified surface. The concentration of Ni gradually decreased from the surface to interior. The maximum content of Ni atoms was nearly 90%. The modified layer was composed of TiNi, Ti2Ni and Ti phases. The maximum microhardness of the Ni modified layer was about 677 HV_0.025 which was increased about two-fold of microhardness of the control Ti6Al4V substrate. Wear resistance of the Ni modified layer was improved obviously, and showed micro-abrasion wearing. The strengthened mechanism of the as-treated Ti6Al4V alloy is discussed.     

Microstructure and oxidation behaviour of SiC fibre-reinforced Si3N4-AlN-Al2O3-Y2O3 matrix composites

A series of SiC fibre-reinforced Si₃N₄-AlN-Al₂O₃-Y₂O₃ matrix composites with different matrix compositions are fabricated by slurry infiltration followed by hot pressing at 1600°C for 30 min. The diffusion of yttrium and aluminium into fibres is apparent during the high temperature processing. All the as-processed composites show fracture with fibre pull-out. After heat treatment in air at 1000°C for 60 min, composites with minimal Y₂O₃ and Al₂O₃ in the matrix composition demonstrate the fracture behaviour with most extensive fibre pull-out. Composites with the highest aluminium and yttrium oxide content form an yttrium–aluminium–garnet phase and an aluminosilicate glassy phase. The latter phase provides an oxygen diffusion path, resulting in the removal of the carbon-rich interphase by oxidation. This results in catastrophic fracture without fibre pull-out after heat treatment of the composite in air.     

Microstructure and wear resistance of Al–SiC composites coatings on ZE41 magnesium alloy

Al and Al–SiC composites coatings were prepared by oxyacetylene flame spraying on ZE41 magnesium alloy substrates. Coatings with controlled reinforcement rate of up to 23 vol.% were obtained by spraying mixtures containing aluminium powder with up to 50 vol.% SiC particles. The coatings were sprayed on the magnesium alloy with minor degradation of its microstructure or mechanical properties. The coatings were compacted to improve their microstructure and protective behaviour. The wear behaviour of these coatings has been tested using the pin-on-disk technique and the reinforced coatings provided 85% more wear resistance than uncoated ZE41 and 400% more than pure Al coatings.     

Effects of particle/matrix interface and strengthening mechanisms on the mechanical properties of metal matrix composites

A randomly distributed multi-particle model considering the effects of particle/matrix interface and strengthening mechanisms introduced by the particles has been constructed. Particle shape, distribution, volume fraction and the particles/matrix interface due to the factors including element diffusion were considered in the model. The effects of strengthening mechanisms, caused by the introduction of particles on the mechanical properties of the composites, including grain refinement strengthening, dislocation strengthening and Orowan strengthening, are incorporated. In the model, the particles are assumed to have spheroidal shape, with uniform distribution of the centre, long axis length and inclination angle. The axis ratio follows a right half-normal distribution. Using Monte Carlo method, the location and shape parameters of the spheroids are randomly selected. The particle volume fraction is calculated using the area ratio of the spheroids. Then, the effects of particle/matrix interface and strengthening mechanism on the distribution of Mises stress and equivalent strain and the flow behaviour for the composites are discussed.     

Assessment of interface deformation and fracture in metal matrix composites under transverse loading conditions

The transverse properties of unidirectional metal matrix composites (MMCs) are dominated by the fiber/matrix interfacial properties, residual stresses and matrix mechanical response. In order to monitor and study, in situ, the failure of interfaces in titanium-based composites subjected to transverse loading conditions, an ultrasonic imaging technique has been developed. The interface was imaged ultrasonically and the change in ultrasonic amplitude with the transverse loading was monitored, indicating the sensitivity of the technique to fracture and deformation of interfaces. This change in amplitude has been explained in terms of the multiple reflection theory of ultrasonic waves. The multiple reflection theory enabled estimation of the interfacial deformation and debonding as a function of loading. The ultrasonic technique was also used in conjunction with finite element modeling in order to quantify the fiber/matrix interfacial transverse strength in situ in MMCs.     

Mechanical and tribological enhancement of polyoxymethylene-based composites with long basalt fiber through melt pultrusion

Abstract

The polyoxymethylene (POM)/basalt fiber composites were prepared by use of long fiber-reinforced thermoplastic technology through melt pultrusion. The mechanical and tribological properties, morphology, and thermal stability of the resulting composites were investigated. The composites exhibit significant improvements in tensile, flexural, and notched impact strength. These mechanical strength and toughness are dependent on the fiber content over the full range of the study. The residual fiber length and distribution in the injection-molded specimens were characterized. The prominent reinforcement effect of basalt fiber on POM is derived from the supercritical fiber length, which is much longer than that of the short fiber-reinforced ones and thus makes the composites take full advantage of the strength of the reinforcing fibers. The Kelly–Tyson model was used to predict the ultimate tensile strength of POM composites using the measured values of residual fiber length in the matrix, but the deviations were observed at the high contents of basalt fiber. The morphologic investigation indicates that the fiber pullout and fiber breakage both contribute energy dissipation to the tensile fracture of the composites. The tribological characterization indicates that the friction coefficients and specific wear rates of POM composites also decrease remarkably. Such an improvement of tribological performance is due to the presence of the high wear-resistant basalt fibers on the top of the worn surface bearing the dynamic loadings under sliding. Moreover, the dynamic mechanical analysis reveals that the storage moduli of the composites increase with increasing the fiber content, whereas the loss factors present an opposite trend.     

Synthesis of ceramic composites using three-dimensional nanostructuring (reinforcement) of alumina matrix with TiN and SiC nanostructures and study of their mechanical properties

The paper considers a new 3D nanostructuring technology of next-genergtion ceramic composites based on a ceramic matrix reinforced with titanium nitride (TiN) gnd silicon carbide (diC). Research data are reported on the formation of TiN and diC nanostructures on the surface of disperse alumina during successive gas chemisorption of organic Ti(N(CH₃)₂)₄ (tetrakis-dimethylamino-titanium, TDMAT) and ammonia NH₃ in the first case and Cl₂Si(CH₃)₂ and methane CH₄ in the second. Such chemisorption increases the number of surface-attached Ti-N groups crystallized on annealing at 1100°C with the formation of a TiN or a SiC nanoparticle layer. According to X-ray diffraction and electron microscopy, TiN nanoparticles with an average size of about 40 nm are formed on the surface of alumina particles after TDMAT and NH₃ treatment for 2 h and subsequent annealing at 1100°C. The mechanical properties of compacted α-A1₂O₃-based ceramics reinforced with TiN and SiC nanoparticles excel the properties of the best ceramic materials provided by different manufacturers.     

A TiB2 metal matrix composite coating enriched with nitrogen: Microstructure and wear properties

Metal matrix composites containing titanium nitrides or titanium borides raise great interest to researchers due to their high wear resistance and enhanced corrosion properties. In the present investigation composite coatings containing both titanium nitrides/carbonitrides and titanium diborides were produced on plain steel substrates using the plasma transferred arc (PTA) technique with argon-nitrogen mixtures in the plasma and shielding gas. The microstructure of the metal matrix composites (MMC) obtained was thoroughly studied and found to consist of primary titanium diboride particles surrounded by a eutectic matrix containing, apart from ferrite, both titanium diboride and titanium carbonitride particles. The wear behavior of the composite coatings was assessed by pin on disk experiments. The wear rate against both a tool steel counterbody and an alumina counterbody is of the order of 10⁻⁴ mm³/m. The friction coefficient for both the alloyed layer-tool steel system and the alloyed layer-alumina system increases up to sliding speed of 0.30 m/s and then decreases, when the sliding speed increases further. Specifically, the friction coefficients are varied between the values 0.5 and 0.65. The wear mechanism for the tribosystem alloyed layer-tool steel is characterized by plastic deformation and adherence of material coming from the alloyed layer to the surface of the ball, while for the tribosystem alloyed layer-alumina ball, severe plastic deformation and formation of oxide layer are observed.     

Model of electroless Ni deposition on SiCp/Al composites and study of the interfacial interaction of coatings with substrate surface

Metallization techniques based on electroless plating are used to coat SiC_p/Al composite materials. The directly palladium chloride (PdCl₂) solutions in HCl is used to render the surface of such non-conductive substrates catalytically active towards metal deposition in the electroless plating solution. The microstructures of Ni-coated composites provided by scanning electron microscope (SEM) bring light into the palladium activation and electroless coating process. Also, X-ray photoelectron spectroscopy (XPS) and Line-scan have allowed to monitor the chemical and compositional surface modifications of activated and coated SiC_p/Al composites, as well as to understand the mechanisms of the catalyst (palladium species) chemisorption on the composites surface and the interaction mechanisms of Ni layer with the SiC_p/Al composites. The experimental results show that a nickel-substrate bonding action takes place during plating. Ni atom existing on the surface of the composites can partially obtain electrons from metals Al of the SiC_p/Al composites when the substrate is embedded in the Ni layers, that is, the orbital interaction through the mutual overlap of the electronic orbits does exist in the interfacial regions between the coated Ni atoms and composites substrate instead of the mechanical-interlocked form. On the basis of the evidence, a model of electroless Ni deposition on SiC_p/Al composites is submitted including Pd activation and Ni deposition processes to describe the formation of catalytic centers and the growth of deposited layer. The deposition model reveals that metal-substrate bond plays an important role in the high adhesion strength between the Ni coatings and the composites.     

Shear and distensile fracture behaviour of Ti-based composites with ductile dendrites

The room-temperature deformation and fracture behaviour of Ti-based composites with ductile dendrites, prepared by copper mold casting and arc-melting techniques, was investigated. Under compressive loading, the Ti-based composites display high fracture strength (about 2000?MPa) and good ductility (about 4 or 10%). The yield strength of the Ti-based composites is relatively low (about 565–923?MPa). However, they have a large strain-hardening ability before failure, due to the interactions between shear bands and dendrites. For the arc-melted Ti-based composites, fracture often occurs in a shear mode with a high plasticity (about 10%). In contrast, the cast Ti-based composites break or split into several parts with a compressive plasticity of 4%, rather than failing in a shear mode. A new fracture mechanism, i.e. distensile fracture, is proposed for the first time to elucidate the failure of the as-cast Ti-based composites. Based on the difference in the fracture modes of the differently prepared composites, the relationships between shear and distensile fracture mechanisms and the corresponding fracture criteria are discussed.     

Experimental analysis of the linear and nonlinear behaviour of composites with delaminations

An analysis of the linear and nonlinear vibration responses of composites with delaminations is presented. The effect of delamination size on the linear and nonlinear vibration response is studied. The composite material used in this paper is a glass fibre reinforced plastic (GFRP) having delaminations at the plies interfaces. The experimental procedure consists in inducing the specimen on its resonance flexural modes with different excitation levels (amplitudes) for six bending modes and for each delamination length. The presence of the nonlinearity introduced by the delamination was clearly identified by the variation of natural frequencies for increasing excitation levels. Then, nonlinear elastic parameters for progressive delamination length were determined and discussed for the first six bending modes. The linear and the nonlinear elastic parameters were compared in their sensitive modes.     

Influence of Ni deposition and subsequent N ion implantation at different substrate temperatures on nano-structure and corrosion behaviour of type 316 and 304 stainless steels

Ni thin films of 250 nm thicknesses were coated on type 304 and 316 stainless steels and post N⁺ ion implanted at 15 keV energy with a fluence of 5 × 10¹⁷ N⁺ cm⁻² at different substrate temperatures. Surface nano-structure of the samples were analysed using X-ray diffraction (XRD), atomic force microscopy (AFM) before corrosion test and scanning electron microscopy (SEM) after corrosion test. Corrosion behaviour of the samples in 1.0 M H₂SO₄ solution was investigated by means of potentiodynamic technique. Nano-structure and crystallography of the films showed the development of Ni₃N(1 1 1) and Ni₄N(2 0 0) orientations with a minimum surface roughness and grain size at 400 K substrate temperature. The highest corrosion resistance with a corrosion current of 0.01 μA cm⁻² (for SS(316)) and 0.56 μA cm⁻² (for SS(304)) was achieved in case of samples which were N⁺ ion implanted at 400 K. Results for both types of stainless steels showed good agreement and the better performance of SS(316) was attributed to the 2% molybdenum contents in the alloy composition of this type of stainless steel, which enhances the effectiveness of nitrogen in retarding the corrosion process.     

Charge transport properties of composites of multiwalled carbon nanotube with metal catalyst and polymer: application to electromagnetic interference shielding

We report charge transport properties such as d.c. conductivity (σ_DC) and its temperature dependence for composites of poly(methyl methacrylate) (PMMA) and multiwalled carbon nanotubes (MWCNTs). The MWCNTs were synthesized through chemical vapor deposition with Fe or Co as catalyst. The MWCNTs were homogeneously dispersed in PMMA matrix through sonication to prepare MWCNT–PMMA composite films. We controlled mass concentration of MWCNTs in the composites, and the thickness of MWCNT–PMMA composite films was 20–400 μm. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy were used to study structure and homogeneity of the composites. The σ_DC at room temperature of MWCNT–PMMA composites increased as mass concentration of MWCNTs increased, which followed percolation theory. Electromagnetic interference (EMI) shielding efficiency (SE) of MWCNT–PMMA composites was measured in the frequency range of 50 MHz–3.5 GHz. We observed the increase of EMI SE of MWCNT–PMMA composites with increasing the concentration of MWCNTs.     

Morphologies,microstructures, and mechanical properties of samples produced using laser metal deposition with 316 L stainless steel wire

Laser metal deposition (LMD) with a filler has been demonstrated to be an effective method for additive manufacturing because of its high material deposition efficiency, improved surface quality, reduced material wastage, and cleaner process environment without metal dust pollution. In this study, single beads and samples with ten layers were successfully deposited on a 316 L stainless steel surface under optimized conditions using a 4000 W continuous wave fibre laser and an arc welding machine. The results showed that satisfactory layered samples with a large deposition height and smooth side surface could be achieved under appropriate parameters. The uniform structures had fine cellular and network austenite grains with good metallurgical bonding between layers, showing an austenite solidification mode. Precipitated ferrite at the grain boundaries showed a subgrain structure with fine uniform grain size. A higher microhardness (205–226 HV) was detected in the middle of the deposition area, while the tensile strength of the 50 layer sample reached 669 MPa. In addition, ductile fracturing was proven by the emergence of obvious dimples at the fracture surface.     

Synthesis and characterization of Co (Ni or Cu)-MCM-41 mesoporous molecular sieves with different amount of metal obtained by using microwave irradiation method

Co (Ni or Cu)-MCM-41 mesoporous molecular sieves with different amount of metal were synthesized by using cetyltrimethyl ammonium bromide as a template and by a novel microwave irradiation method. These samples were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and N₂ physical adsorption. The experimental results show that Co (Ni or Cu)-MCM-41 mesoporous molecular sieves were successfully synthesized. When the as-synthesized samples were calcined at 550 °C for 10 h, the template was effectively removed. Under microwave irradiation condition, Co-MCM-41 mesoporous molecular sieves have specific surface areas in a range of 745.7-1188.8 m²/g and average pore sizes in a range of 2.46-2.75 nm; Ni-MCM-41 mesoporous molecular sieves have specific surface areas in a range of 625.8-1161.3 m²/g and average pore sizes of ca. 2.7 nm; Cu-MCM-41 mesoporous molecular sieves have specific surface areas in a range of 601.6-1142.9 m²/g and average pore sizes in a range of 2.46-2.76 nm. On the other hand, with increasing the introduced metal amount, the specific surface area and pore volume of the synthesized Co (Ni or Cu)-MCM-41 mesoporous molecular sieves became small, and the mesoporous ordering of the samples became poor. Under the comparable synthesis conditions, the synthesized Co-MCM-41 mesoporous molecular sieve has a bigger specific surface area and a more uniform pore distribution as compared with the synthesized Ni-MCM-41and Cu-MCM-41 mesoporous molecular sieves.