Effects of polyvinylidene fluoride sealing on micro-arc oxidation coating of 7075 aluminum alloy

Purpose The purpose of this is to study the effects of organic sealing on the structure and performance of the micro-arc oxidation (MAO) film of 7075 aluminum alloy. Design/methodology/approach The 7075 aluminum alloy was treated by micro-arc oxidation technology, then the MAO films were sealed by polyvinylidene fluoride (PVDF) solutions with different concentrations to forms a MAO/PVDF composite coating on the surface of the 7075 aluminum alloy matrix. Findings The results show that the MAO/PVDF film thickness increased to 24.8 um. When the PVDF concentration was 8 g/L, and the sealed film reached best corrosion resistance and wear resistance. Originality/value The effects of different concentrations of PVDF on microarc oxidation properties of 7075 aluminum alloy were studied.

Influence of the thickness and porosity of the oxide coating on the piston heads depending on the parameters of the microarc oxidation mode

This paper discusses the process of formation of an oxide coating (hardening and heat-insulating coating) on the working surfaces of the head (top and piston grooves) of the piston by the method of microarc oxidation (MAO). In the process of oxidation of the piston head, the operating parameters of MAO will have a significant effect on the thickness and porosity of a formed oxide coating. The paper presents the theoretical relationships between the electrical parameters of the microarc oxidation mode and the thickness and porosity of the oxide coating. The thickness of the formed oxide coating on the piston heads will depend on the applied voltage and the composition of the electrolyte used. The porosity of the formed oxide coating will depend on the parameters of the current strength and the applied voltage. It is theoretically established that the formation of an oxide coating of a certain thickness and porosity occurs due to changes in the current strength, voltage and time of microarc oxidation.

Influence of the parameters of the process conditions for microarc oxidation on the formation of the thickness and porosity of the oxide coating

The process of formation of an oxide coating (strengthening and heat-insulating one) on the working surfaces of the piston head (piston bottom and grooves) using the method of micro-arc oxidation (MAO) is discussed. It is noted that during the oxidation of the piston head, the MAO process conditions will have a significant effect on the thickness and porosity of the oxide coating formed. The theoretical dependences of the influence of the electrical parameters of the microarc oxidation process conditions on the thickness and porosity of the oxide coating are presented. It has been found that the thickness of the oxidized layer will be directly proportional to the voltage and composition of the electrolyte, and the porosity is inversely proportional to the voltage and directly proportional to the current strength. It is shown that by varying the parameters of the oxidation conditions (current strength, voltage and process time), oxidized layers of the required thickness and porosity can be obtained.

Developing technology of creating wear-resistant ceramic coating for internal combustion engine cylinder sleeve

This paper presents the results of testing a wear-resistant ceramic coating on the work surface of an internal combustion engine (ICE) cylinder’s sleeve. A combined coating formation technology is described that consists in applying an aluminum layer to the sleeve’s work face by gas dynamic spraying and then covering this face with a ceramic layer by microarc oxidation (MAO). A tenfold reduction in the reinforced sleeve has been determined by the accelerated comparative wear rig tests of reference (new) sleeve-piston ring coupling specimens and reinforced specimens with a combined coating. The supplementation of nanoparticle admixture to MAO coating reduces the friction factor between the cylinder sleeve face and the piston ring by 25-30%. The proposed technology can be used to reinforce work surfaces of new cylinder sleeves and recover worn out ones.

Osteoblast Response to Copper-Doped Microporous Coatings on Titanium for Improved Bone Integration

Due to their excellent mechanical properties and good biocompatibility, titanium alloys have become a popular research topic in the field of medical metal implants. However, the surface of the titanium alloy does not exhibit biological activity, which may cause poor integration between the interface of the titanium implant and the interface of the bone tissue and subsequently may cause the implant to fall off. Therefore, surface biological inertness is one of the problems that titanium alloys must overcome to become an ideal orthopedic implant material. Surface modification can improve the biological properties of titanium, thereby enhancing its osseointegration effect. Copper is an essential trace element for the human body, can promote bone formation and plays an important role in maintaining the physiological structure and function of bone and bone growth and development. In this study, a microporous copper-titanium dioxide coating was prepared on the surface of titanium by microarc oxidation. Based on the evaluation of its surface characteristics, the adhesion, proliferation and differentiation of MC3T3-E1 cells were observed. A titanium rod was implanted into the rabbit femoral condyle, and the integration of the coating and bone tissue was evaluated. Our research results show that the microporous copper-titanium dioxide coating has a nearly three-dimensional porous structure, and copper is incorporated into the coating without changing the structure of the coating. In vitro experiments found that the coating can promote the adhesion, proliferation and differentiation of MC3T3-E1 cells. In vivo experiments further confirmed that the titanium copper-titanium dioxide microporous coating can promote the osseointegration of titanium implants. In conclusion, copper-titanium dioxide microporous coatings can be prepared by microarc oxidation, which can improve the biological activity and biocompatibility of titanium, promote new bone formation and demonstrate good osteoinductive properties. Therefore, the use of this coating in orthopedics has potential clinical application.