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Ti(C, N) coatings were prepared on stainless steel (SS) substrates by plasma surface alloying technique. Carbon–nitrogen co-doped titanium dioxide (C-N-TiO₂) coatings were fabricated by oxidative of the Ti(C, N) coatings in air. The prepared C-N-TiO₂ coatings were characterized by SEM, XPS and XRD. Results reveal that the SS substrates were entirely shielded by the C-N-TiO₂ coatings. The C-N-TiO₂ coatings are anatase in structure as characterized by X-ray diffraction. The tribological behavior of the coatings was tested with ball-on-disc sliding wear and compared with substrate. Such a C-N-TiO₂ coatings showed good adhesion with the substrate and tribological properties of the SS in terms of much reduced friction coefficient and increased wear resistance.

This paper describes the fabrication of a Cu-coating on pure titanium via plasma surface alloying technology. The surface morphology, cross-sectional microstructure and elemental distributions of the coating were analyzed by scanning electron microscope (SEM) and glow discharge optical emission spectroscope (GDOES). The antibacterial property of the Cu-coating was assessed via in vitro bacterial adhesion test. The results showed that the Cu-coating was continuous and compact. The Cu-coating endowed pure titanium with a promising antibacterial property.

Cu–Cr alloyed layers with different Cu and Cr contents on pure titanium were obtained by means of plasma surface alloying technology. The microstructure, chemical composition and phase composition of Cu–Cr alloyed layers were analyzed by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD), respectively. The experimental results demonstrate that the alloyed layers are bonded strongly to pure titanium substrate and consist of unbound Ti, CuTi, Cu₃Ti, CuTi₃ and Cr₂Ti. The thickness of Cu₅Cr₅ and Cu₇Cr₃ alloyed layer are about 18 μm and 28 μm, respectively. The antibacterial properties against gram-negative Escherichia coli (E.coli, ATCC10536) and gram-positive Staphylococcus aureus (S. aureus, ATCC6538) of untreated pure titanium and Cu–Cr alloyed specimen were investigated by live/dead fluorescence staining method. The study shows that Cu–Cr alloyed layers exhibit excellent antibacterial activities against both E.coli and S.aureus within 24 h, which may be attributed to the formation of Cu-containing phases.

Plasma surface alloying (PSA) technique was employed with nickel as incident ions to prepare the TiNi/Ti₂Ni alloyed layer on surface of Ti6Al4V. High-temperature friction and wear performance of TiNi/Ti₂Ni alloyed layer and the Ti6Al4V substrate were evaluated at 500${}^{\circ }$C. The results indicated that the TiNi/Ti₂Ni alloyed layer exhibited superior high-temperature wear performance. The variations of friction coefficient were the same rule but wear rate was lower compared to Ti6Al4V substrate. The wear mechanism of TiNi/Ti₂Ni alloyed layer was mainly slight abrasion and the Ti6Al4V substrate showed abrasion and oxidation wear. The friction coefficient of the TiNi/Ti₂Ni alloyed layer decreased from 0.90 to 0.50 with the increase of temperature from room temperature to 500${}^{\circ }$C.

In order to improve the performance of the Ti6Al4V (TC4) spur gear, a Mo surface modified layer is prepared by the plasma surface metallurgy technique. The element concentration, microstructure and elastoplastic properties are investigated with glow-discharge optical emission spectroscope (GDOES), scanning electron microscope, optical microscope (OM) and nanoindenter. Engaging with 41Cr4 steel gears, the wear resistances of the treated and untreated TC4 spur gears are evaluated through running-in and operation tests performed by a friction and wear tester under lubricated conditions. By finite element analysis, contact stress distributions in the TC4 and 41Cr4 spur gears pair are quantitatively determined. The results indicate that, being compact and uniform, the Mo-modified layer has higher hardness and retains relatively fine plasticity. The wear resistance of the treated TC4 spur gear is improved significantly.

The aim of this paper is to establish an approach to quantitatively determine the elasto-plastic parameters of the Mo-modified Ti obtained by the plasma surface alloying technique. A micro-indentation test is conducted on the surface under 10N. Considering size effects, nanoindentation tests are conducted on the cross-section with two loads of 6 and 8mN. Assuming nanoindentation testing sublayers are homogeneous, finite element reverse analysis is adopted to determine their plastic parameters. According to the gradient distributions of the elasto-plastic parameters with depth in the Mo-modified Ti, two types of mathematical expressions are proposed. Compared with the polynomial expression, the linear simplified expression does not need the graded material to be sectioned and has practical utility in the surface treatment industry. The validation of the linear simplified expression is verified by the micro-indentation test and corresponding finite element forward analysis. This approach can assist in improving the surface treatment process of the Mo-modified Ti and further enhancing its load capacity and wear resistance.