Mechanical and tribological characteristics of a-C:H:SiOx films formed by PACVD on titanium alloy VT1-0

This paper is devoted to the study of the mechanical and tribological properties of aC:H:SiOx films deposited on a titanium alloy VT1-0 by a plasma chemical deposition method using pulsed bipolar bias voltage. It was shown that after deposition of 2 [mu]m-thick a-C:H:SiOx film on a titanium alloy VT1-0 sample, the root-mean-square surface roughness Rq measured using atomic force microscopy decreased from 74 to 50 nm compared to the original substrate. The surface hardness H measured using nanoindentation increased from 3.3 to 12.4 GPa with an almost unchanged elasticity modulus E. As a result, the plasticity index (H/E) of titanium samples increased from 0.03 to 0.11, and the plastic deformation resistance (H3/E2 ) increased from 3 to 156 MPa. Deposition of a-C:H:SiOx film on the titanium alloy VT1-0 surface makes possible to reduce the friction coefficient from 0.3-0.6 to 0.1 and the wear rate from 6·10-4 to 7•10{-6} mm{3} /Nm

Исследование реакции тромбоцитов на a-C:H:SiOx покрытие, полученное методом плазмохимического осаждения с использованием импульсного биполярного смещения

Aim. To study platelet adhesion to a-C:H:SiOx film on titanium in an in vitro experiment to evaluate its antithrombogenic potential.Materials and methods. Thin (less than 1 μm) a-C:H:SiOx films were deposited on VT-6 titanium plates with a size of 10 × 10 mm2 and a thickness of 0.2 mm using a vacuum ion-plasma unit using pulsed bipolar bias. The surface roughness was evaluated according to GOST 2789-73 using an atomic force microscope. The test samples were cultured at 37 °C for 30 min in platelet-rich human blood plasma, prepared for scanning electron microscopy, after which the distribution density of blood plates adhering to the test coating was calculated.Results. With the same roughness index of the studied a-C:H:SiOx samples, the film decreased 116 times (in comparison with untreated titanium) the platelet count per 1 mm2 of the surface.Conclusion. The deposition of a-C:H:SiOx thin film on the surface of VT-6 titanium alloy by PACVD method using pulsed bipolar bias significantly reduces the distribution density of platelets in comparison with an untreated metal surface. In vitro data suggest a significant antithrombogenic potential of this type of coating on the surface of devices in contact with blood.Цель. Изучить в эксперименте in vitro адгезию тромбоцитов к a-C:H:SiOx пленке на титане для оценки ее атромбогенного потенциала.Материалы и методы. Тонкие (менее 1 мкм) a-C:H:SiOx пленки наносили на титановые пластины марки ВТ-6 размером 10 × 10 мм2 и толщиной 0,2 мм с помощью вакуумной  ионно-плазменной установки с использованием импульсного биполярного смещения.  Шероховатость поверхности оценивали согласно ГОСТ 2789-73 с помощью атомно-силового микроскопа. Исследуемые образцы культивировали при 37 °C в течение 30 мин в плазме крови человека, обогащенной тромбоцитами, подготавливали для сканирующей электронной микроскопии, после чего подсчитывали плотность  распределения кровяных пластинок, адгезирующих к исследуемому покрытию.Результаты. При одинаковом индексе шероховатости исследуемых образцов a-C:H:SiOx пленка в 116 раз снижала (в сравнении с необработанным титаном) количество  тромбоцитов на 1 мм2 поверхности.Заключение. Формирование на поверхности титанового сплава ВТ-6 тонкой пленки состава a-C:H:SiOx методом плазмохимического осаждения с использованием  импульсного биполярного смещения значительно снижает плотность распределения  тромбоцитов в сравнении с необработанной металлической поверхностью. Полученные in vitro данные предполагают существенный атромбогенный потенциал данного вида покрытий на поверхности устройств, контактирующих с кровью

(Cr1−xAlx)N Coating Deposition by Short-Pulse High-Power Dual Magnetron Sputtering

The paper deals with the (Cr1−xAlx)N coating containing 17 to 54 % Al which is deposited on AISI 430 stainless steel stationary substrates by short-pulse high-power dual magnetron sputtering of Al and Cr targets. The Al/Cr ratio in the coating depends on the substrate position relative to magnetrons. It is shown that the higher Al content in the (Cr1−xAlx)N coating improves its hardness from 17 to 28 GPa. Regardless of the Al content, the (Cr1−xAlx)N coating manifests a low wear rate, namely (4.1–7.8) × 10−9 and (3.9–5.3) × 10−7 mm3N−1m−1 in using metallic (100Cr6) and ceramic (Al2O3) counter bodies, respectively. In addition, this coating possesses the friction coefficient 0.4–0.7 and adhesive strength quality HF1 and HF2 indicating good interfacial adhesion according to the Daimler-Benz Rockwell-C adhesion test

Properties of TiAlN Coatings Obtained by Dual-HiPIMS with Short Pulses

The paper focuses on the dual high-power impulse magnetron sputtering of TiAlN coatings using short pulses of high power delivered to the target. The surface morphology, elemental composition, phase composition, hardness, wear resistance, and adhesive strength of TiAlN coatings with different Al contents were investigated on WC–Co substrates. The heat resistance of the TiAlN coating was determined with synchrotron X-ray diffraction. The hardness of the TiAlN coating with a low Al content ranged from 17 to 30 GPa, and its wear rate varied between 1.8∙10−6 and 4.9∙10−6 mm3·N−1·m−1 depending on the substrate bias voltage. The HF1–HF2 adhesion strength of the TiAlN coatings was evaluated with the Daimler–Benz Rockwell C test. The hardness and wear rate of the Ti0.61Al0.39N coating were 26.5 GPa and 5.2∙10−6 mm3·N−1·m−1, respectively. The annealing process at 700 °C considerably worsened the mechanical properties of the Ti0.94Al0.06N coating, in contrast to the Ti0.61Al0.39N coating, which manifested a high oxidation resistance at annealing temperatures of 940–950 °C

Properties of TiAlN Coatings Obtained by Dual-HiPIMS with Short Pulses

The paper focuses on the dual high-power impulse magnetron sputtering of TiAlN coatings using short pulses of high power delivered to the target. The surface morphology, elemental composition, phase composition, hardness, wear resistance, and adhesive strength of TiAlN coatings with different Al contents were investigated on WC–Co substrates. The heat resistance of the TiAlN coating was determined with synchrotron X-ray diffraction. The hardness of the TiAlN coating with a low Al content ranged from 17 to 30 GPa, and its wear rate varied between 1.8∙10−6 and 4.9∙10−6 mm3·N−1·m−1 depending on the substrate bias voltage. The HF1–HF2 adhesion strength of the TiAlN coatings was evaluated with the Daimler–Benz Rockwell C test. The hardness and wear rate of the Ti0.61Al0.39N coating were 26.5 GPa and 5.2∙10−6 mm3·N−1·m−1, respectively. The annealing process at 700 °C considerably worsened the mechanical properties of the Ti0.94Al0.06N coating, in contrast to the Ti0.61Al0.39N coating, which manifested a high oxidation resistance at annealing temperatures of 940–950 °C

In Vitro Biodegradation of a-C:H:SiO_x Films on Ti-6Al-4V Alloy

This paper focuses mainly on the in vitro study of a five-week biodegradation of a-C:H:SiOx films of different thickness, obtained by plasma-assisted chemical vapor deposition onto Ti-6Al-4V alloy substrate using its pulsed bipolar biasing. In vitro immersion of a-C:H:SiOx films in a solution of 0.9% NaCl was used. It is shown how the a-C:H:SiOx film thickness (0.5–3 µm) affects the surface morphology, adhesive strength, and Na+ and Cl− precipitation on the film surface from the NaCl solution. With increasing film thickness, the roughness indices are reducing a little. The adhesive strength of the a-C:H:SiOx films to metal substrate corresponds to quality HF1 (0.5 µm in thickness) and HF2-HF3 (1.5–3 µm in thickness) of the Rockwell hardness test (VDI 3198) that defines strong interfacial adhesion and is usually applied in practice. The morphometric analysis of the film surface shows that on a-C:H:SiOx-coated Ti-6Al-4V alloy surface, the area occupied by the grains of sodium chloride is lower than on the uncoated surface. The reduction in the ion precipitation from 0.9% NaCl onto the film surface depended on the elemental composition of the surface layer conditioned by the thickness growth of the a-C:H:SiOx film. Based on the results of energy dispersive X-ray spectroscopy, the multiple regression equations are suggested to explain the effect of the elemental composition of the a-C:H:SiOx film on the decreased Na+ and Cl− precipitation. As a result, the a-C:H:SiOx films successfully combine good adhesion strength and rare ion precipitation and thus are rather promising for medical applications on cardiovascular stents and/or friction parts of heart pumps