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In the present study, Ti–Al–V–N coatings were synthesized onto Ti–6Al–4V substrates by plasma enhanced magnetron sputtering (PEMS) of two commercial sputter targets of Ti–6Al–4V in an Ar/N 2 gas mixture. After that, the as-synthesized coatings were annealed in air atmosphere at temperature ranging from 500 °C to 900 °C. The as-synthesized and annealed coatings were characterized by X-ray diffraction, Vickers microhardness tester, ball-on-disk tribometer and potentiodynamic polarization tests. The as-synthesized coatings showed a surface hardness of about 2980 ± 80 HV 0.3 and a friction coefficient of 0.36. It has been revealed with the increase of annealing temperature; the microhardness was gradually decreased and reached a minimum value of 1030 ± 30 HV 0.3 at 900 °C. The coefficient of friction has a minimum value of 0.27 for coatings annealed at 600 °C. Potentiodynamic polarization test confirmed that thermally annealed samples (≤600 °C) exhibit a better corrosion performance compared to that of the as-synthesized one. However, at relatively higher annealing temperature (700–900 °C), a small degradation in the corrosion performance was observed with the formation of oxidized phases. Finally, the variation in the mechanical and tribological properties of this coating with annealing temperatures is attributed to changes in microstructure and chemical nature of the surface layer. [ABSTRACT FROM AUTHOR]

This study is one part of a series of efforts to optimize the microstructure and tribological properties of the Ti–Si–C–N coatings for a wide range of industrial applications. In this study, Ti–6Al–4V samples were coated with thick Ti–Si–C–N coatings (25–35 μm) using a plasma enhanced magnetron sputtering (PEMS) process, in which Ti was sputtered from two magnetrons at fixed power of 4 kW for each magnetron in a reactive environment of Ar, N 2 and trimethylsilane (TMS). The substrate power density (ion bombardment power density) was varied by varying the bias voltage and the ion flux, which was varied by changing the electron emission current in the PEMS process. After the depositions, scanning electron microscopy (SEM) and X-ray diffractometry (XRD) were used to study the microstructure and morphology of these coatings. Nano-indentation was performed to study the surface hardness H and modulus of elasticity E , from which the ratios of H / E * and H 3 / E * 2 were calculated, where E * = E / (1 − ν 2 ) and ν is the Poisson's ratio. The solid particle erosion (SPE) resistance of the coatings was evaluated using a sand blaster with 50 μm alumina particles at two incident angles of 30° and 90°. Finally, an electrochemical test was conducted to determine the coating corrosion resistance. It was found that all coatings had a nanocomposite microstructure. But the coatings produced at the higher substrate power densities (0.13–0.20 W/cm 2 ) had a smaller crystallite size (5.2–5.8 nm) with a better morphological quality, i.e. free from columnar structure, defects or delamination. The substrate power density has a strong influence on the surface hardness and the ratios of H / E * and H 3 / E * 2 . The higher the substrate power density, the higher these values. The solid particle erosion resistance and corrosion resistance of the coatings also correlated well with the substrate power density. Coatings deposited at higher power densities of ion bombardment exhibited better erosion resistance and corrosion resistance than those deposited at lower substrate power densities. [ABSTRACT FROM AUTHOR]

Abstract: Titanium nitrides have good mechanical, biomedical and optical properties, therefore they are used to harden and protect cutting and sliding surfaces and as a non-toxic exterior for bio-medical applications. Nitrogen plasma immersion implantation (PIII), in which the diffusion of nitrogen from low pressure r.f. plasma is combined with the implantation of nitrogen ions at energies up to 30kV, is an effective tool for nitriding titanium and titanium alloys. In this work, samples of pure titanium were nitrided by PIII at different negative high voltage pulses. The properties and the characteristics of the processed samples were evaluated using X-ray diffraction (XRD), Auger electron spectroscopy (AES), ball-on-disk type tribometer, surface profilemeter, and ellipsometry measurements. The results show that, the wear resistance of the untreated sample in comparison to the PIII treated samples is extremely poor and the friction coefficient for the PIII treated samples is decreased to the half value in comparison to the untreated titanium, this attributed to the formation of the solid solution titanium α-Ti(N) and the cubic TiN phases. Ellipsometric measurements were carried out on the PIII treated samples at different negative high voltage pulses. A three layers model was used to fit the calculated data to the experimental ellipsometric spectra. The thickness, surface roughness and refractive index increase with increasing the negative high voltage pulses. The refractive index at 550nm increases from 1.83 to 2.09 as the negative high voltage pulses increases from 10 to 30kV. [Copyright &y& Elsevier]

Abstract: AISI-304 austenitic stainless steel has been nitrocarburized in N2 and C2H2 ambient using high-voltage plasma immersion ion implantation (PIII) technology. The use of different PIII treatment times revealed important hints with respect to the microstructural, mechanical and corrosion properties of the nitrocarburized layer. Grazing incidence X-ray diffraction (GIXRD) shows the presence of nitride (γ N and CrN) and carbide (γ C and Fe3C) phases. Glow discharge optical spectroscopy (GDOS) has been used to characterize the elemental depth profiles in which the thickness of the modified layers is derived. Dynamic microindentation method is used for the study of mechanical performance of the nitrocarburized layer as well as the untreated material. The microhardness has been increased to a maximum value of more than nine times compared to that of the untreated one. The corrosion performance is characterized by potentiodynamic polarization technique and was found to be treatment time dependent. [Copyright &y& Elsevier]

Abstract: The present work describes the surface improvement and biocompatibility of TiAl24Nb10 intermetallic alloy using rf plasma nitriding. The nitriding process was carried out at different plasma power from 400W to 650W where the other plasma conditions were fixed. Grazing incidence X-ray diffractometry (GIXRD), Auger electron spectroscopy (AES), tribometer and a nanohardness tester were employed to characterize the nitrided layer. Further potentiodynamic polarization method was used to describe the corrosion behavior of the un-nitrided and nitrided alloy. It has been found that the Vickers hardness (HV) and corrosion resistance values of the nitrided layers increase with increasing plasma power while the wear rates of the nitrided layers reduce by two orders of magnitude as compared to those of the un-nitrided layer. This improvement in surface properties of the intermetallic alloy is due to formation of a thin modified layer which is composed of titanium nitride in the alloy surface. Moreover, all modified layers were tested for their sustainability as a biocompatible material. Concerning the application area of biocompatibility, the present treated alloy show good surface properties especially for the nitrided alloy at low plasma power of 400W. [Copyright &y& Elsevier]

Abstract: ZnO thin films were prepared by thermal oxidation of metallic Zn films and nitrided by an inductively coupled rf plasma. The effects of successive plasma processing cyclic times on structural and optical properties as well as electrical resistivity were examined by different characterization techniques. A small amount of nitrogen was detected at the film–substrate interface. The grain size decreased slightly as the treatment time increased. The surface roughness of examined films increased while the thickness decreased with increasing plasma treatment time. The electrical resistivity decreased about four orders of magnitude when the sample nitrided for 15min. However, the transmittance increased as the plasma treatment time increased. The optical band gap increased from 2.76 to 3.02eV with increasing plasma treatment time from 0 to 15min. [Copyright &y& Elsevier]

Abstract: Plasma immersion ion implantation (PIII) has been employed for nitrocarburizing 304 stainless steel. The sample was treated at relatively low gas pressure of nitrogen and acetylene in the range of 10−3 mbar. The microstructure variation, the austenite lattices spacing and the phase transformations were studied in-situ during heating up to 800 °C and after cooling, using synchrotron X-ray diffraction. Glow discharge optical spectroscopy (GDOS), optical microscopy and hardness profile measurements have been used before and after thermal treatment to analyse the nitrocarburized layer. [Copyright &y& Elsevier]

The depth dependence of elemental composition, phase distribution, and cross-sectional morphology of rf plasma nitrocarburized 304 austenitic stainless steel were investigated using glow discharge optical spectroscopy (GDOS), grazing incidence X-ray diffraction (GIXRD), and optical microscopy, respectively. A step-wise mechanical polishing method was used to remove successive sublayers of the treated surface. It was found that the properties of the nitrocarburized layer depend critically on the plasma gas composition, which controls the supersaturation of nitrogen and carbon through the compound layer depth. Iron nitride phases and/or nitrogen-expanded austenite (γN) were detected in the nitrocarburized layer prepared at high plasma nitrogen (N2) content. In the compound layer processed at high plasma carbon (C2H2) content, besides the carbon-expanded austenite phase (γC), carbide phases were found predominantly in the top-layer, in which the carbon concentration has a maximum value of ∼2 wt.%. The lattice expansion of the expanded austenite phases changes with sampling depth, depending on local variations in nitrogen and carbon content. The applied rf plasma processing power influences significantly nitrogen and carbon distribution in the treated sublayers. [Copyright &y& Elsevier]

Abstract: Plasma immersion ion implantation (PIII) has been used to modify the surface properties of 304 austenitic stainless steel (AISI). The influence of working gas pressure, 0.2–1.0 Pa, and substrate temperature, 300–500 °C, on the microstructure, treating rate, nitrogen/carbon concentration depth profile, and surface microhardness was investigated. A gas composition of 25% C2H2, 75% N2, r.f. plasma power input of 350 W, and a negatively biased potential of 30 kV were fixed during the experiment. The experimental results show that the substrate temperature and the diffusion process of nitrogen and carbon depend on the gas pressure inside the plasma chamber. The thickness of the modified layer has been found to be more than 30 μm for samples were treated in the plasma for 60 min. The results show also that the values of diffusion coefficient and surface microhardness of the treated samples are high to be 3.4×10−1 μm2/s and 1880 kg/mm2, respectively. [Copyright &y& Elsevier]

Adding C2H2 gas to nitrogen gas during r.f. plasma processing has significant influence on the properties of 304 austenitic stainless steel. The elemental depth profiles of the compound layer were investigated by glow discharge optical spectroscopy. Different treatment gas compositions of N2/C2H2 mixtures (0–100% in steps of 10 or 5% in some cases) have been investigated. The total gas pressure during the plasma processing was 8.4×10-2 mbar. The sample temperature was approximately 550 °C with an insignificant variation for different gas compositions. A high rate of diffusion of carbonitriding has been obtained without initial sputter removal of the surface oxide layer, which demonstrates that the surface oxide layer does not play a crucial role during r.f. plasma carburizing and carbonitriding of stainless steel. The nitrogen concentration and the compound layer thickness increase, when 10% of C2H2 is added. With further increase in the C2H2 ratio, they decrease again gradually. The carbon depth profiles for the same samples show lower concentration and opposite tendency with respect to the nitrogen content. X-ray diffraction was used to characterize the microstructure of the compound layers. Fe2N, Fe3N, CrN, nitrogen-expanded austenite (γn) and carbon-expanded austenite (γc) phases are detected. The relative proportions of the phases are critically dependent on the N2/C2H2 ratio. Depending on the N2/C2H2 ratio, the microhardness value increases by a factor between 2 and 6. The carbonitrid layer exhibits a corrosion resistance better than pure nitrided and carburized layers. [Copyright &y& Elsevier]

• TiO x N y films capped with 10 nm TiO 2 layer are prepared by reactive sputtering. • TiO 2 /TiO x N y are examined for photoelectrochemical (PEC) water splitting. • The optical properties are controlled by nitrogen content in TiO 2 /TiO x N y films. • Annealing could increase the PEC performance of TiO 2 /TiO x N y bilayer films. • Wettability changed from hydrophobic to hydrophilic with ultraviolet illumination. Titanium oxynitride (TiO x N y) films capped with 10 nm titanium oxide (TiO 2) layer were prepared using reactive direct current magnetron sputtering from pure Ti target. Part of the samples was annealed. Energy dispersive analysis of X-ray revealed that all the samples contain nitrogen and the incorporation of nitrogen into the oxynitrides is not linear. Phase investigation by X-ray diffraction showed structural variation with changing oxygen and nitrogen gas flow rates as well as annealing. Anatase, brookite, rutile and titanium nitride were detected individually or mixed in the as-prepared and annealed samples. The optical properties were found to be controlled by a structure and chemical composition. Transmittance and reflectance measurements were carried out by a high performance double beam ultraviolet-visible-near infrared spectrophotometer. Based on that, the energy band gap, refractive index and extinction coefficient were derived. The obvious difference between the dark and light currents indicated the validity of the TiO 2 /TiO x N y bilayer samples to act as photoanodes. All the annealed samples have photoelectrochemical water splitting response better than the as-prepared samples. The as-prepared TiO 2 /TiO x N y bilayer films were hydrophobic (contact angels, 81° - 93°) and their contact angles were independent from the nitrogen content. The annealed samples have lower contact angles than the as-prepared samples. The wettability of the as-prepared and annealed samples was changed from hydrophobic to more hydrophilic with increasing illumination time. These results are of important interest for the self-cleaning surfaces. [ABSTRACT FROM AUTHOR]

Titanium nitrides have good tribo-mechanical and biomedical properties. They are employed to harden and protect cutting and sliding surfaces for industrial purpose and as a non-toxic outer-surface for bio-medical applications. In this study, pure titanium was nitrided using RF plasma technique. The microstructural, mechanical, tribological, electrochemical and biomedical properties of nitrided titanium were investigated. The X-ray diffraction demonstrates the formation of ε-Ti 2 N and the cubic δ-TiN phases after plasma nitriding. The microhardness of the nitride samples increases as the plasma-processing power increases up to 1300 HV 0.1 . That represents approximately 7-fold increment in the microhardness in comparison with the untreated titanium. High nitriding rate of 0.17 μm 2 /s was recorded for the sample that was treated at 650 W. The wear and corrosion resistance are improved after plasma nitriding. Moreover, the friction coefficient is reduced from nearly 0.75 for the untreated titanium to 0.25 for the nitride one. An enhancement in the biocompatibility of the nitrided titanium has been achieved. The number of grown mesenchymal stem cells was higher for nitrided substrates compared to that of the untreated titanium. The improved tribo-mechanical and electrochemical performance of the nitrided titanium can be attributed to the formation of super-hard titanium nitrided phases. [ABSTRACT FROM AUTHOR]

Abstract: Surface of 304 AISI austenitic stainless steel has been modified using duplex treatment technique of nitriding and carbonitriding. A thick modified nitrided layer, of approximately 20 µm, has been achieved when rf inductively coupled plasma was adjusted at 450 W for processing time of only 10 min. After performing the nitrided layer, the nitrided samples were carbonitrided using the same technique at different acetylene partial pressure ratios ranges from 10% to 70%, the balance was pure nitrogen. Different amount of nitrogen and carbon species are diffused underneath the surface through the nitrided layer during carbonitriding process and are found to be gas composition dependent. The treated samples were characterized by glow discharge optical spectroscopy, X-ray diffractometry, scanning electron microscopy and Vickers microhardness tester. The microstructure of the duplex treated layer indicates the formation of γ́-Fe4N, Fe3C, CrN and nitrogen-expanded austenite (γN). The thickness of the duplex treated layer increases with increasing the acetylene partial pressure ratio. The surface microhardness of duplex treated samples has been found to be gas composition dependent and increased by 1.29 fold in comparison to the nitrided sample. [Copyright &y& Elsevier]