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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: 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: 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]

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]