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Abstract: Amorphous AlPO4 based ceramic coatings with 13μm thick were prepared on Ti–6Al–2Zr–1Mo–1V titanium alloy surface using amorphous aluminum phosphate as a binder and Al2O3/Cr2O3 based mixing particles as the fillers. The phase composition and microstructure of the coated samples before and after exposing oxidation test were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). After exposing oxidation at 600°C for 100h, no oxide scales were found either at coating/substrate interface or on coating surface, exhibiting a significantly lower weight gain (0.07mg/cm2) compared with the bare titanium (0.54mg/cm2). After exposing oxidation at 800°C, the TiO2 dominated oxide scales began to form on coating surface after oxidation for 5h and at coating/substrate interface after oxidation for 60h, finally got weight gain of 1.4mg/cm2 after oxidation for 100h. The coating had a higher infrared emissivity value (>0.8) than titanium substrate (0.15–0.3) in the wide wavelength range of 3–20μm, which was attributed to the uniform dispersion of high emissivity Al2O3 and Cr2O3 particles in the amorphous AlPO4 binder matrix. [Copyright &y& Elsevier]

Abstract: Ceramic coatings were formed on the surface of Ti6Al4V alloy by microarc oxidation (MAO) in a Na2SiO3 system solution using a pulsed bipolar power supply. The microstructure, phase and elemental composition of the ceramic coatings were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The distribution of mechanical properties across the coating and its adhesion strength were determined by a nanoindentation and a shear test respectively. The tribological properties were evaluated using a pin-on-disk wear tester. The results show that the coatings are mainly composed of rutile and a small amount of anatase TiO2, with amorphous compounds from electrolyte components incorporated. The hardness and elastic modulus are about 8.5 GPa and 87.4 GPa for the compact region of the coating, and about 4 GPa and 150 GPa for the substrate. Similar profiles of hardness and elastic modulus along the coating of about 45 μm thickness is found, and both values in the compact region remain mainly constant before finally declining to below those of the substrate in the outer loose region. The adhesion strength is about 70 MPa. The friction coefficient of the coating against steel is as low as 0.2–0.3 at <1 N load and at <2500 sliding cycles. However, the oxidation wear mechanism occurring at the later stage of wear tests leads to a gradual increase of friction coefficient. [Copyright &y& Elsevier]

Bioactive composite coatings with a microarc oxidation (MAO) bottom layer and a biomimetic top hydrothermal layer were developed on an AZ31B magnesium alloy by combined MAO and hydrothermal treatment. The composition and microstructure of the coatings were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Potentiodynamic polarization and soaking test in simulated body fluid (SBF) were used to evaluate the biodegradation and bioactivity of coated magnesium. The results show that the bioactive top hydrothermal layer containing CaHPO 4 , HA and Ca 3 (PO 4 ) 2 grows on a 10 μm thick MAO bottom layer. The corrosion current of samples with MAO-hydrothermal duplex layers is reduced to 4.780 × 10 − 6 A cm − 2 , the corrosion potential is increased to − 0.92 V. The sealing pore effect of the top hydrothermal layer enabled the MAO bottom layer to obtain a significantly improved corrosion resistance property. The MAO-hydrothermal sample had a weight increase of 14.52 mg cm − 2 compared to 24.7 mg cm − 2 weight loss for the MAO bottom layer after 28 days, due to the CaP compound deposition induced by the top hydrothermal surface. [ABSTRACT FROM AUTHOR]

Abstract Tungsten films (750–1200 nm thick) deposited by high-power impulse magnetron sputtering (HiPIMS) under various sputtering gas pressure and substrate bias are investigated for their physical and microstructural characteristics. Compared to films deposited by the traditional direct current (DC) method with the same deposition configuration and similar parameters, HiPIMS materials exhibit higher hardness, a smoother surface, and better adhesion to a substrate. These excellent properties are attributed to the highly uniform grain structures developed during HiPIMS deposition, in contrast to the funnel shaped grains seen in DC sputtered films. Combined with the in-situ stress measurements, we discuss the underlying mechanisms that lead to enhanced properties of HiPIMS tungsten films. Highlights • Tungsten films were deposited with HiPIMS to 1 μm thickness. • HiPIMS films showed physical characteristics superior to basic DC sputtered films. • Highly compressive average stress was measured during deposition for all films. • HiPIMS film compressive stress was highest without substrate bias. [ABSTRACT FROM AUTHOR]