Tribological behavior of electrodeposited Zn,Zn–Ni,Cd and Cd–Ti coatings on low carbon steel substrates

The tribological behavior of electrodeposited Zn–Ni alloy coatings was investigated for its suitability to replace Zn- and Cd-based coatings. An in situ tribometry technique with a transparent sapphire hemisphere as a counter face on a pin on flat tribometer was utilized to examine the contribution of third bodies in friction and wear behavior. Wear mechanisms and tribo/transfer film morphology were also studied with the X-ray diffraction and electron microscopy. In situ tribometry and additional ex situ analyses revealed that Zn–Ni coatings had superior resistance to adhesive wear compared to cadmium coatings. Microhardness of Zn–Ni coatings was higher than Zn and Cd coatings. Hardness on the wear track of Zn–Ni coatings showed the formation of a strain hardened tribo layer.     

Effects of electromagnetic stirring and rare earth compounds on the microstructure and mechanical properties of hypereutectic Al–Si alloys

In this paper, the effects of rare earth addition and electromagnetic stirring on the microstructure and the mechanical properties of hypereutectic Al–Si alloys have been reported. Hypereutectic Al–Si alloy was prepared using liquid metallurgy route and modified with the addition of cerium oxide. To control the structure, slurry of hypereutectic Al–Si alloy was subjected to electromagnetic stirring before pouring into the mould. It was observed that the addition of cerium oxide (0.2 wt.%) refined the primary silicon particles and modified the eutectic silicon particles. Further, the electromagnetic stirring of the hypereutectic Al–Si alloy reduced the average size of primary silicon particles, from 152?±?9 to 120?±?6 μm, and the length of β-intermetallic compounds decreased from 314?±?12 to 234?±?10 μm. Similarly, the application of electromagnetic stirring on cerium oxide-modified hypereutectic Al–Si alloy also reduced the average size of primary silicon particles from 98?±?5 to 76?±?4 μm and the average length of β-intermetallic compounds from 225?±?7 to 203?±?5 μm. Mechanical properties namely tensile strength, ductility and hardness of the alloys were improved with electromagnetic stirring and addition of cerium oxide appreciably.     

A study of densification and on factors affecting the density of Ni x –Fe100 − x nanopowders prepared by mechanical alloying and sintered by spark plasma

Mechanical alloying through high-energy ball milling was used in the production of Ni–Fe alloy powders from elemental Ni and Fe powders of average particle size 80 and 25 μm, respectively. High-energy planetary ball milling at room temperature was performed for various time durations ranging between 2 and 100 h. SPS apparatus was used for sintering of powder particles. Density of all specimens was reported and a maximum densification of 99 % was achieved in 50 wt.% Ni–Fe milled for 16 h prior to spark plasma sintering at 1,223 K.     

The effect of equal channel angular pressing on the mechanical and magnetic properties of 09Γ2C steel

The physical and mechanical properties of 09Γ2C steel that was subjected to strengthening by intense plastic deformation using the method of equal channel angular pressing (ECAP) are studied. An unambiguous interrelationship between the magnetic (coercive force, maximal permeability, Barkhausen magnetic noise parameters) and mechanical (rupture limit, conditional yield strength, relative elongation and narrowing upon damaging) characteristics of 09Γ2C steel, which was strengthened using ECAP following different technological regimes, is demonstrated. Therefore, it is possible to estimate the strength and plasticity characteristics of the analyzed material based on the measurement of its magnetic parameters. It has been revealed that under conditions of uniaxial tension in the range from 0 to (0.2–0.6) of the conditional yield strength (depending on the ECAP regime), it is possible to diagnose changes in the stressed state of items that are made of 09Γ2C steel that is hardened in accordance with the ECAP technique using magnetic structuroscopy methods.     

Mechanical and tribological properties of Cr–Nb double-glow plasma coatings deposited on Ti–Al alloy

Double-glow plasma (DGP) coatings are recommended for metallic components to mitigate the damage induced by complex working conditions in previous studies. In this paper, Nb-rich (Cr–Nb₄) and Cr-rich (Cr₄–Nb) -alloyed layers were formed onto the Ti–Al substrate via a DGP process to enhance its wear resistance. Scratch and Nano-indentation tests were used to evaluate the mechanical properties of the coatings. The tribological behaviour of the coatings were investigated using a pin-on-disc tribometer by rubbing against the GCr15 ball. Results from surface analysis techniques showed that the coatings mainly comprised Cr, Nb and Cr₂–Nb phases, and were well bonded to the substrate. The hardness of the Cr–Nb₄ coating was 11.61GPa and the Cr₄–Nb coating was 9.66 GPa which all higher than that of the uncoated Ti–Al which was 5.65 GPa. However, the critical load of the Cr₄–Nb coating ~21.64 was higher than that of the Cr–Nb₄ coating ~17.6. And the specific wear rate of Cr–Nb₄ coating, Cr₄–Nb coating and uncoated Ti–Al were 3.54 × 10^?4, 0.01 × 10^?4 and 1.53 × 10^?4mm³ N^?1 m^?1_, respectively. The low-wear mechanism of the coatings is discussed in detail in this paper.     

Effect of deformation martensite on the electrical and magnetic properties of plastically deformed chromium–nickel steel

Connection between the structural and phase changes in specimens of chromium–nickel austenitic steel and their magnetic and electrical properties has been studied. It has been established that electric resistivity can be used as an additional testing parameter for the phase composition of plastically deformed articles made of austenitic-ferritic steel. It has been shown that the emergence of an additional phase of strain-induced martensite leads to a significant increase in electric resistivity.     

The effects of nickel and carbon concentrations on the wear resistance of Fe–Ni–C austenitic alloys

The effects of nickel and carbon concentrations on the wear resistance of Fe–xNi–yC (x = 14–20 wt.%, y = 0.6–1.0 wt.%) were investigated with respect to strain energy initiation of the martensitic transformation and hardness. The strain energy needed to initiate the martensitic transformation increased with increasing carbon and nickel concentrations, except in 1.0 wt.% C alloys. The wear resistance of the material decreased with increasing carbon concentration up to 0.9 wt.% C. This effect is most likely due to decrement of the martensite volume fraction with increasing carbon concentration induced by the incremental strain energy required to begin the martensitic transformation. In the case of 1.0 wt.% C, the improved wear resistance may be due to carbide precipitation.     

Novel investigation on tribological properties of Ni–P–Ag–Al2O3 hybrid nanocomposite coatings

In this research, silver and alumina particles were co-deposited within Ni–P matrix to obtain Ni–P–Ag–Al₂O₃ hybrid coating. The structure of coatings was analyzed by X-ray diffraction and the tribological properties of deposits were evaluated by pin on disc tribometer. 3D optical profiler and scanning electron microscopy were used to study wear rate and worn surfaces. The results showed that Ni–P–Ag and Ni–P–Ag–Al₂O₃ coatings have the self-lubrication property and maximum hardness (∼1310 HV) and wear resistance were obtained for Ni–P–Al₂O₃ coating. Also, Ni–P–Ag–Al₂O₃ hybrid nanocomposite coating had higher wear resistance than Ni–P and Ni–P–Ag coatings. Moreover, the best conditions was achieved for heat treated hybrid coating in the concentration of 30 mg/L silver and 150 mg/L alumina in the plating solution.     

Plasma–powder application of antifrictional babbitt coatings modified by carbon nanotubes

Modification of Babbitt coatings by carbon nanotubes in plasma–powder application is considered. A model is proposed for the interaction of a graphene-like surface and atoms from the Babbitt alloy. The influence of carbon nanotubes obtained by different means on the performance of antifrictional coatings is studied.     

Effects of Chromium Addition on Microstructure and Abrasion Resistance of Fe–B Cast Alloy

This research work studies the effects of chromium on microstructure and abrasion resistance of Fe–B cast alloy. The results show that eutectic boride changes from continuous network to less continuous and matrix changes from pearlite to martensite with the increase in chromium content in the alloy. Meanwhile, an increase in chromium addition in the alloy leads to an increase in the chromium content in M₂B-type boride because chromium can enter boride by substituting for iron in Fe₂B. Under two-body wear, Fe–B cast alloy exhibits excellent wear resistance. When alloys are tested against soft abrasive, chromium can markedly improve the wear resistance of Fe–B cast alloy, whereas excessive chromium can reduce the wear resistance. The wear resistance of Fe–B cast alloy increases first and then decreases with the increase in chromium. But when tested against hard abrasive, since the hardness of SiC is much higher than that of M₂B boride, an increase in chromium content marginally increases the wear resistance. Weight losses of Fe–B cast alloy increase with the increase in the load and exhibit the linear relationship.     

Mechanical and tribological properties of sputtered Mo–Se–C coatings

Transition metal dichalcogenides belong to the more developed class of materials for solid lubrication. However, the main limitation of these materials is the detrimental effect of air humidity causing an increase in the friction. In previous works, molybdenum diselenide has been shown to be a promising coating retaining low friction even in very humid environment. In this study, Mo–Se–C films were deposited by sputtering from a C target with pellets of MoSe₂. Besides the evaluation of the chemical composition, the structure, the morphology, the hardness and the cohesion/adhesion, special attention was paid to the tribological characterization.The C content varied from 29 to 68 at.% which led to a progressive increase of the Se/Mo ratio. As a typical trend, the hardness increases with increasing C content. The coatings were tested at room temperature with different air humidity levels and at temperatures up to 500 °C on a pin-on-disc tribometer. The friction coefficient of Mo–Se–C coatings increased with air humidity from ～0.04 to ～0.12, while it was as low as 0.02 at temperature range 100–250 °C. The coatings were very sensitive to the elevated temperature being worn out at 300 °C due to adhesion problems at coating–titanium interface.     

Effect of matrix/reinforcement particle size ratio (PSR) on the mechanical properties of extruded Al–SiC composites

This paper studied the combined effects of matrix-to-reinforcement particle size ratio (PSR) and SiC volume fraction on the mechanical properties of extruded Al–SiC composites. A powder metallurgy technique (PM) of cold pressing at 500 MPa followed by hot extrusion at 580 °C was adopted to produce Al/SiC composite. Aluminum powder of size 60 μm and silicon carbide with different sizes, i.e., 50, 20, and 8 μm, were used. Three different volume fractions of SiC were employed, i.e., 5, 10, and 15 %, for each investigated size using a constant extrusion ratio of 14.36. The effect of matrix-to-reinforcement PSR on the reinforcement spatial distribution, fabricability, and resulting mechanical properties of a PM-processed Al/SiC composite were investigated. It has been shown that small ratio between matrix to reinforcement particle size resulted in more uniform distribution of the SiC particles in the matrix. As the PSR increases, the agglomerations and voids increase and the reinforcement particulates seem to have nonuniform distribution. In addition, the agglomerations increased as the volume fraction of the SiC increased. It has also been shown that homogenous distribution of the SiC particles resulted in higher yield strength, ultimate tensile strength, and elongation. Yield strength and ultimate tensile strength of the composite reinforced by PSR (1.2) are higher than those of composite reinforced by PSR (7.5), while the elongation shows opposite trend with yield strength and ultimate tensile strength.     

Wear and corrosion behavior of electrodeposited nickel–carbon nanotube composite coatings on Ti–6Al–4V alloy in Hanks′ solution

Carbon nanotubes (CNT) have received considerable interest in many industries, but composite coatings of CNTs have not yet been sufficiently developed for use in biomedical implants. This investigation elucidates the wear and corrosion behavior of electroplated Ni/CNT composite coatings on Ti–6Al–4V alloy in Hanks’ solution. Experimental results indicate that the CNTs in an electroplated Ni/CNT composite coating increase its hardness to 98.5% higher than that of a pure Ni coating. Additionally, an Ni/CNT composite coating can form stable and dense passive film, which significantly improves wear and corrosion in Hanks′ solution.     

Effect of Melting and Microstructure on the Microscale Friction of Silver–Bismuth Alloys

This article reports an investigation of the effect of melting and microstructure on the microscale friction of several silver–bismuth alloys using a high-temperature nanoindentation-tribotesting system. These studies showed that friction increases with temperature before melting. We modeled these results as due to the softening of the alloys with increasing temperature, which appears to adequately explain the experimental trend. The friction behavior upon melting depends on the alloy composition. For some alloy composition, friction was observed to exhibit a sharp decrease upon melting, while for another alloy composition, friction was observed to keep increasing with temperature. This unusual behavior can be explained by the difference in microstructure and phase composition as a function of temperature among different Ag–Bi alloys.     

Tribological behavior of plasma electrolytic oxidation coatings on the surface of Mg–8Li–1Al alloy

Plasma electrolytic oxidation coatings were fabricated on the surface of Mg–8Li–1Al. The tribological behavior of the coated and uncoated Mg–Li alloy was investigated under dry friction conditions against a Si₃N₄ ball as counter-face material. The results indicated that the tribological behavior is greatly affected by the microstructure and phase compositions of the coatings. The PEO coatings significantly improved the properties of friction and wear of Mg–Li alloy.     

A comparative study on the wear properties of coarse-grained Al6061 alloy and nanostructured Al6061–Al2O3 composites

Wear behavior of nanostructured Al6061 alloy and Al6061–Al₂O₃ nanocomposites produced by milling and hot consolidation were investigated. The samples were characterized by hardness test, pin-on-disk wear test, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Nanocomposites containing 3 vol% Al₂O₃ showed a maximum hardness of 235 HV and optimum wear rate of 4×10⁻³ mg/m. Increasing the amount of Al₂O₃ up to 5 vol% resulted in decrease in hardness values (∼112 HV) and a sharp rise in wear rate (∼18×10⁻³ mg/m).     

Frictional and adhesive behavior of organic–inorganic hybrid coatings on surgical grade stainless steel using nano-scratching technique

Because of their mechanical properties, metals are the most widely used materials as orthopaedic implants. However they cannot provide a natural bond with the mineralized bone and they also release metallic particles due to degradation or tribologic events. One way to improve the metallic implants performance is to apply protective organic–inorganic sol–gel coatings. In this work, stainless steel substrates are coated with films made by a sol–gel technique from organosilane precursors.Although mechanical properties of similar films have been studied, there is no information about adhesion, friction or deformation processes of silica-based hybrid films to stainless steel substrates.Hybrid coatings with higher amount of inorganic components (called TMH) have almost no elastic response and the debris due to chipping or delamination does not persist into the indentation trace. With the film with high content of organic compounds was found elastic recovery in early stages of loading and there is evidence of pile-up at the edges of the trace with higher load applied. After the unloading the film has a persistent deformation and is removed due to the asynchronic recovery of the film and the substrate. The combined two-film coating shows a lot of debris in the trace. This is an unusual but possible behavior of polymeric coatings and could be attributed to different recoveries between the first inorganic layer (called TEOS–MTES), the substrate and the upper TMH film. This fact produces delamination and crack formation in the TEOS–MTES coating, inducing tensile efforts, and finally the upper film is pulled-off.     

Comparative assessment of the mechanical and electromagnetic surfaces of explosively clad Ti–steel plates after drilling process

The present work pertains to the analysis of surface topography of explosively clad material such as titanium plated steel in drilling process. The study was conducted for different types of indexable insert drills with different configuration of the tool coatings and for WC-Co drill tool. In this context, surface topography of the drilled holes especially in the region of contact area was analyzed. Metrological analysis was performed using stylus-based and optical profilometry. In this paper the differences between mechanically and electromagnetically measured surfaces are highlighted. It has been observed that the parameters of the surface topography are dependent upon the type of layers of the clad and the type of drill.     

Cavitation resistance of Cr–N coatings deposited on austenitic stainless steel at various temperatures

Cr–N coatings were deposited on austenitic stainless steel, X6CrNiTi18-10, by means of the cathodic arc evaporation method at three substrate temperatures: 200 °C, 350 °C and 500 °C. All coatings were found to have a composition of Cr(N), CrN and Cr₂N. The substrate temperature was found to have an influence on the hardness and Young's modulus of the Cr–N coatings. The investigation of nanocrystalline Cr–N coatings resistance to cavitation was performed in a cavitation tunnel with a slot cavitator and tap water as the medium. The estimated cavitation resistance parameters of the coatings were the incubation period of damage and total mass loss. It was found that the optimal coating cavitation resistance was deposited at 500 °C. The incubation period for the 500 °C deposition coating was the same as that of the uncoated X6CrNiTi18-10 steel, but the total mass loss was significantly lower than on the uncoated specimen. The scanning electron microscope analysis indicated that the damage process of the Cr–N coating mainly originates from the plastic deformation of the steel substrate–hard coating system, which appears by “micro-folding” of the surface. An increase of tensile stresses at the top of micro-folds initiates micro-cracks and delamination of Cr–N coating. The results of the investigation and the analysis indicate that the factors mainly responsible for cavitation resistance of the steel substrate/hard coating system are resistant to plastic deformation of the total system and coating adhesion.