Electrophoretic Deposition,Microstructure, and Corrosion Resistance of Porous Sol–Gel Glass/Polyetheretherketone Coatings on the Ti-13Nb-13Zr Alloy

Metallurgical and Materials Transactions A - In this study, microporous composite sol–gel glass/polyetheretherketone (SGG/PEEK) coatings were produced on the Ti-13Nb-13Zr titanium alloy by...     

Effect of Low-Friction Composite Polymer Coatings Fabricated by Electrophoretic Deposition and Heat Treatment on the Ti-6Al-4V Titanium Alloy’s Tribological Properties

Metallurgical and Materials Transactions A - In this work, polytetrafluoroethylene/polyetheretherketone (PTFE/PEEK 708) coatings were fabricated by electrophoretic deposition (EPD) and heat...     

Nanohardness and tribological properties of nc-TiB2 coatings

The work is devoted to the investigation of nanohardness and tribological properties in TiB₂ coatings deposited on austenitic steel substrates using an unbalanced magnetron sputtering with the focus on the coatings prepared under small negative bias to reduce compressive stresses. The coating prepared under floating potential exhibited nanocomposite microstructure with the size of TiB₂ (hcp) nanocrystallites in the range of 2–7 nm. It is in contrast with the textured microstructure typically developed under higher negative bias. The reduction of the compressive stresses up to ?0.4 GPa while keeping the nanohardness >30 GPa and the coefficient of friction of 0.77 were obtained in this coating. The highest nanohardness of 48.6 ± 3.1 GPa and indentation modulus of 562 ± 18 GPa were achieved at ?100 V bias in the textured coating. The friction mechanisms include mechano-chemical formation of a tribological oxide film between the sliding partners combined with an abrasive wear.     

Microstructure and Selected Properties of Advanced Biomedical n-HA/ZnS/Sulfonated PEEK Coatings Fabricated on Zirconium Alloy by Duplex Treatment

In this work, sulfonated polyetheretherketone (S-PEEK)-based coatings, nanocrystalline ZnS and hydroxyapatite (n-HA) particles were developed on Zr-2.5Nb zirconium alloy substrates by electrophoretic deposition (EPD) combined with subsequent heat treatment. The properties of suspensions and deposition kinetics were studied. Cationic chitosan polyelectrolyte ensured the stabilization of the suspension and allowed for the co-deposition of all coating components on the cathode. The heating of the coated samples at a temperature of 450 °C and slow cooling resulted in sulfonation of the PEEK and the formation of dense coatings. The coatings were characterized by high roughness, hardness, modulus of elasticity and adhesion strength. The coatings revealed mild hydrophilicity, improved the electrochemical corrosion resistance of the alloy and induced the formation of hydroxyapatite with a cauliflower-like morphology on its surface during the Kokubo test. This work explored the great development potential of advanced sulfonated PEEK-based coatings, incorporating antibacterial and bioactive components by EPD combined with heat treatment to stimulate the surface properties of zirconium alloy for prospective dental and orthopedic applications. The antibacterial and osteoconductive properties of the obtained coatings should be further investigated.     

Microstructure, properties and oxidation behavior of the glass-ceramic based coating on near-α titanium alloy

Protective SiO₂-Al₂O₃-CaO-Na₂O glass-ceramic based coating produced on TIMETAL 834 by slurry technique was investigated. Analytical scanning and transmission electron microscopy as well as X-ray diffraction were used for detailed analyses of a microstructure and chemical composition of the coating. It was found that the coating contains crystalline phases: CaSiO₃, NaAlSiO₄, Na₂CaSiO₄ and amorphous phase containing mainly O, Si and Al. It was established that glass-ceramic coating formed on TIMETAL 834 essentially improves the alloy selected properties, e.g. its hardness and high temperature oxidation resistance.     

Thick Low-Friction nc-MeC/a-C Nanocomposite Coatings on Ti-6Al-4V Alloy: Microstructure and Tribological Properties in Sliding Contact with a Ball

In this paper, we show that duplex surface treatment, combining oxygen diffusion hardening with the subsequent deposition of thick, low-friction nanocomposite nc-MeC/a-C coatings to improve the tribological properties of the Ti-6Al-4V alloy. We have synthesized, in a magnetron sputtering process, the nanocomposite nc-MeC/a-C coatings (where Me denotes W or Ti transition metal) consisting of two dissimilar materials (nanocrystallites of transition metal carbides MeC and an amorphous carbon matrix a-C). The nano and microstructure of the substrate material and coatings were examined with the use of scanning and transmission electron microscopy as well as by X-ray diffractometry. It was found that different carbide nanocrystals of the same transition metal were embedded in an amorphous carbon matrix of both coatings. The HRTEM analysis indicated that the volume fraction of tungsten carbides in the nc-WC/a-C coating was equal to 13 pct, whereas in the nc-TiC/a-C one the volume fraction of the titanium carbides was equal to just 3 pct. The tribological properties, hardness, and scratch resistance of the coatings were investigated as well. The coefficient of friction (COF) of the coatings during dry sliding against 6 mm diameter alumina ball reached very low value, 0.05, in comparison with an oxygen-hardened alloy, whose COF was equal to 0.8. This low-friction effect of the coatings has been attributed to the formation of a self-lubricating film in sliding contact. The coatings exhibited similar failure morphology in the scratch tests. Even though the hardness was rather low, the coatings exhibited a very good wear resistance during sliding friction. The wear rate of the nc-WC/a-C coating was equal to 0.08 × 10^?6 mm³ N^?1 m^?1 and for the nc-TiC/a-C one it was 0.28 × 10^?6 mm³ N^?1 m^?1.     

Microstructure, mechanical properties and oxidation behavior of the TiAl(Si,Ag) coating on near-α titanium alloy

In order to improve oxidation resistance of TIMETAL834, protective coating based on γ-TiAl intermetallic alloy with Si and Ag admixtures was produced by magnetron sputtering. Analytical scanning and transmission electron microscopy were used for detailed analyses of a microstructure and chemical composition of the coating. It was found that the coating contains two sublayers with different microstructure and morphology. Energy-dispersive synchrotron radiation diffraction was applied for stress analysis. The results show that there are tensile residual stresses present within the TIMETAL834 substrate and compressive residual stresses within the γ-TiAl sublayer. It was established that the surface treatment applied in this work essentially improves the alloy oxidation resistance.     

Development of Microstructure and Properties of Multicomponent MoS2/HA/PEEK Coatings on a Titanium Alloy Via Electrophoretic Deposition and Heat Treatment

Metallurgical and Materials Transactions A - In this study, molybdenum disulfide nanosheets, bioactive hydroxyapatite particles of two types in various amounts, and PEEK 704 microparticles were...     

Microstructure characterisation and stress analysis of the Ti48Al2Ag coating on the near-α titanium alloy

The microstructure and phase composition of the protective Ti48Al2Ag coating produced on Timetal 834 by magnetron sputtering have been examined by scanning and analytical transmission electron microscopy (SEM, TEM). TEM investigations revealed that Ti48Al2Ag coating consists of two sublayers: outer columnar γ-TiAl and amorphous Ti₅Al₃O₂. Energy-dispersive synchrotron radiation diffraction was applied for stress analysis. The results show that there are tensile residual stresses present within the Timetal 834 substrate and compressive residual stresses within the γ-TiAl sublayer.     

Microstructure and tribological properties of low-friction composite MoS2(Ti,W) coating on the oxygen hardened Ti-6Al-4V alloy

Duplex surface treatment, which combines the oxygen diffusion hardening with a deposition of low friction MoS₂(Ti,W) coating, was applied to improve the Ti-6Al-4V alloy load bearing capacity and tribological properties. The coating (3.1 μm thick) was deposited on the oxygen hardened alloy by magnetron sputtering. Microstructure characterisation was performed by scanning- and transmission electron microscopy methods, as well as X-ray diffractometry. The results of micro/nanostructural analyses performed by high-resolution transmission electron microscopy showed that the coatings are composed of MoS₂ nanoclusters embedded in an amorphous matrix. Some Ti α, W, and Ti₂S nanocrystals were also found in the coating microstructure. The wear resistance and friction coefficient of the hardened oxygen, as well as the coated alloy, was investigated at room temperature (RT), 300 °C, and 350 °C. The presence of the MoS₂(Ti,W) coating decreases the friction coefficient from 0.85 for the oxygen hardened alloy to 0.15 (at RT) and 0.09 (at 300 °C and 350 °C) for the coated one. The coating essentially increases the wear resistance of the alloy at RT and 300 °C. It was found that the wear resistance of the coated alloy decreased significantly during the wear test performed at 350 °C.