Hard Anodic Oxide Research Articles

Synthesis of a Hard Anodic Oxide Coating with a Structure Allowing for Its Modification by Nanoparticles

A hard anodic oxide coating’s characteristic porous structure allows for its modification by the incorporation of nanoparticles. However, achieving an appropriate microstructure requires an optimal pore arrangement and shape, which is influenced by the electrolyte composition, current densities, temperature, and processing time. To achieve pores with a diameter of about 50 nm and the most regular structure, a range of these parameters were tested. Using a two-stage manufacturing process had a beneficial effect on increasing the microporosity of the coating. The addition of phthalic acid at 0 °C did not increase the pore diameter, but allowed for the process to be carried out at higher temperatures. However, the coating produced at 20 °C had a larger pore diameter, but numerous defects. The coating obtained from the three-component solution had the most regular structure, but the smallest pore diameter.

Investigation on the properties of anodic oxides grown on aluminium-silicon alloys irradiated by pulsed electron beam

Al-Si alloys are among the most common aluminium based materials for cast products due to theirhigh strength-to-weight ratio, excellent processability and relatively low cost. The presence of Si inthe molten Al phase improves the castability and decreases the solidification shrinkage. Hard anodicoxidation is largely employed to improve their surface mechanical properties and corrosion resistance.However, the presence of high Si contents (> 3%) and the size of Si particles in the alloy makethe process challenging or even not possible. The surface pretreatment of Al-Si alloys with intensepulsed electron beams (EB) can effectively overcome the aforementioned limitations. Electron beamsources can be employed to reduce Si content and to refine and disperse Si particles, and effectivelycreate an Al substrate that is more prone to oxidization. In the present work, two electron beamunits were used, RITM-SP and SOLO, to modify the surface properties of hypoeutectic, eutectic andhypereutectic Al-Si alloys, by investigating the effect of energy density and number of pulses. Theelectron beam treated substrates were hard anodized and characterized in term of microstructure,elemental distribution, corrosion resistance and surface mechanical properties.

Prediction of polishing roughness of aluminum alloy hard anodized film based on BP and GA-BP neural network

In order to obtain better-polished surface quality of hard anodic oxide film, two deep learning models of the BP neural network and GA-BP neural network were used to establish a roughness prediction model for aluminum alloy hard anodic oxide film polishing. The experimental data was divided into two groups, one group of data was used for model training, and the other group of data was used for model testing. The results showed that the mean square error between the polishing roughness predicted by the BP neural network model and the experimental results was 1.33E-2, the maximum relative error was 18.84 %, the minimum relative error was 0.77 %, and the average relative error was 10.46 %. The error is relatively large, and the degree of variation of the error is relatively large; the mean square error of the polishing roughness predicted by the GA-BP neural network model and the test results is 0.58E-2, the maximum relative error is 14.28 %, the minimum relative error is 0.51%, the average relative error is 6.61 %, the error is smaller, and the degree of error change is smaller; the prediction accuracy of the GA-BP model is the highest, and the generalization ability strongest.

Comparative Analysis of Finite Element Simulation and Experiment on the Polished Surface Quality of Hard Anodized Film of Aluminum Alloy

According to the abrasive morphology and distribution of sandpaper surface, the finite element model of hard anodic oxide film polishing was established by using ABAQUS finite element software, and the hard anodic oxide film and aluminum alloy matrix were defined respectively. The effects of hard anodic oxide film polishing process, polishing surface quality and polishing parameters on the polishing force were simulated. The polishing surface quality and polishing force simulated by finite element model were verified by experiments. The results show that in the polishing process, the residual stress of polishing surface is mainly distributed in the range of 0.0034mm, and the chips produced by polishing are mainly broken and long strips with microscopic morphology, and polishing mainly depends on the front part of abrasive particles in the feeding direction of sandpaper. Under the action of abrasive particles of sandpaper, the results of finite element simulation and test show that there are certain grooves on the surface of oxide film. The finite element simulation of the normal polishing force of hard anodic oxide film is consistent with the polishing test results. During the process of polishing hard anodic oxide film, the normal polishing force increases as the polishing speed increases; the normal polishing force increases as the polishing removal amount increases; the polishing removal amount parameter has a greater degree of influence on the polishing force.

EFFECT OF CASE DEPTHS ON CORROSION PROPERTIES OF HARD ANODIC OXIDIZED A356 ALUMINUM ALLOY

In this work, A356 alloy samples having a dimension of [Formula: see text][Formula: see text]mm were coated by hard anodic oxidation method at eight different thicknesses up to [Formula: see text]80[Formula: see text][Formula: see text]m. The sample surfaces and longitudinal section of these surfaces in both coated and uncoated conditions were investigated with a scanning electron microscope (SEM). Microhardness of the coating layers and core regions (base metal) were determined with the microvickers hardness testing method. Corrosion properties of the coated and uncoated samples were investigated by an electrochemical corrosion test set up according to ASTM G5 standard. The test results obtained from the coated and uncoated surfaces were compared to each other. Coated surfaces exhibited fluctuant surface profile. Microcracks were formed on these surfaces. Microhardness of the coating layers increased with increasing coating layer thickness. Energy dispersed X-ray spectroscopy (EDS) analysis of the surfaces showed that oxygen rate on the surfaces increased after the corrosion tests. Corrosion rate of the A356 alloy coated by hard anodic oxidation decreased with increasing coating thickness up to 40–50[Formula: see text][Formula: see text]m, but after this coating thickness, the corrosion rate increased. The results obtained from the investigations were discussed based on the characteristics of the coated surfaces.

Experimental research on the polished surface quality of hard anodized film of aluminum alloy

An experimental study was conducted for the surface polishing of the oxide film after hard anodizing of 2D70 aluminum alloy. The surface roughness and surface morphology of aluminum alloy before, after anodizing and after polishing were analyzed, and the effects of polishing force, polishing speed, feeding amount and sandpaper grit on the polished surface roughness were investigated experimentally. The results showed that the surface roughness of 2D70 aluminum alloy decreased by 1 grade on average after hard anodizing. The hard anodized film surface has more linear protrusions, large pits and a large number of small pores. After polishing, the linear protrusions and small pores disappear, and a small number of new linear grooves appear, while the condition of large pits does not change much. The depth of small pores on the oxide film surface is within 11μm in most cases. As the polishing force, feeding amount and sandpaper grit increase, the decreasing trend of roughness value also gradually increases, and the decreasing trend of the thickness of hard anodic oxide film gradually increases. As the polishing speed increases, there is no clear trend in the decreasing trend of rough

Abrasive-Wheel-Wear Abrasion Resistance Test for Hard Anodic Oxide Coating on the Nonplanar Cylinder Shape Sample

Abrasive-Wheel-Wear Abrasion Resistance Test for Hard Anodic Oxide Coating on the Nonplanar Cylinder Shape Sample

Reactivity of porous titanium oxide film and chitosan layer electrochemically formed on Ti-6Al-4V alloy in biological solution

Uniform porous TiO2 film on Ti-6Al-4V alloy was obtained by hard anodic oxidation and successfully the chitosan layer was electrodeposited. Surface morphology, compositional properties and diffraction patterns were analyzed by scanning electron microscopy with energy dispersive X-ray analysis system and X-ray diffraction. The reactivity of anodic porous TiO2 film in the presence or absence of chitosan layer was investigated by electrochemical methods in biological solution and compared with the reactivity with the unmodified Ti-6Al-4V alloy surface. The electrochemical impedance spectroscopy method was used to compare the response reactivity of the three surfaces. The combination of the high biocompatibility of chitosan and good mechanical characteristics of Ti-6Al-4V alloy make the obtained porous TiO2 film combined with chitosan a promising method to improve the reactivity of medical implants in biological solution.

Composite Coatings with Ceramic Matrix Including Nanomaterials as Solid Lubricants for Oil-Less Automotive Applications

Abstract The paper presents the theoretical basis of manufacturing and chosen applications of composite coatings with ceramic matrix containing nanomaterials as a solid lubricant (AHC+NL). From a theoretical point of view, in order to reduce the friction coefficient of sliding contacts, two materials are required, i.e. one with a high hardness and the other with low shear strength. In case of composite coatings AHC+NL the matrix is a very hard and wear resistant anodic oxide coating (AHC) whereas the solid lubricant used is the nanomaterial (NL) featuring a low shear strength such as glassy carbon nanotubes (GC). Friction coefficient of cast iron GJL-350 sliding against the coating itself is much higher (0.18-0.22) than when it slides against a composite coating (0.08-0.14). It is possible to reduce the friction due to the presence of carbon nanotubes, or metal nanowires.

G031071 硬質アルマイト処理およびKURACERA処理を施したA5052アルミニウム合金試験片の単軸引張りに伴う変形と破壊([G031-07]材料力学部門,一般セッション : 表面処理)

Recently, aluminum alloys are important structural materials because of high specific strength, lightweight, excellent in recycling. Various surface treatments for aluminum alloys have been developed for improvement of corrosion and wear resistances. Among them, environment-friendly anodizing in which oxide coating is formed on the material surface with easy process has been applied to a wide range of structural material. Also, plasma electrolytic oxidation (PEO) treatment was developed. Since KURACERA coating, it is classified PEO coating, is harder than anodic oxide coating, it is expected spacious application. In this study, in order to research the effect of oxide coating on deformation and fracture behavior, hard anodizing and KURACERA treated test specimen were observed with microscope during tensile test and the results were compared. The following results were obtained. With increasing the coating thickness, longitudinal elastic constant of coating, tensile strength and strain at fracture decreased. Longitudinal elastic constant of KURACERA coating was larger than that of hard anodic oxide coating. Also, since surface roughness was large in specimens with thick coating, more stress concentration occurred in thick coating larger and made necking and cracking easy.

Tribological Behavior of Ceramic Surface Layers of Ring and Box Spinning Machines Aluminum Elements Rubbing against Yarn

The paper deals with the influence of hard anodizing coatings on ring and box spinning machines aluminum elements rubbing against the yarn upon the wear of these parts and the quality of the yarn. The process of hard anodic oxidation substantially increases the durability of the chosen parts of spinning frames; i.e, the spindles and rotors. For example, the wear intensity of collecting groove of the rotor without the oxides coating was found to be of 0.42 μm/h, after about 6000 h of work, while after the process of anodic oxidation it decreased to 0.0022 μm/h. On the other hand, in case of a ring spinning frame the wear intensity of the surface of the spindle coat neck without the oxides coating amounted to 0.068 μm/h, while after anodic oxidation it decreased to 0.00048 μm/h.

Assessing the Wear of the Oxide Layer of a Spindle-neck Coating with a Collapsed Balloon Crown

The results of an investigation into the wear of the spindle-neck coating with a collapsed balloon crown of a ring-spinning frame during mating with the yarn under industrial conditions is presented. The investigation included examining the wear of the spindle-neck coating made of aluminum alloy 2024, which was subjected to the following different methods of finishing: grinding with abrasive cloth, burnishing only, and burnishing followed by hard anodic oxidation. The analysis of the process of wear and the thickness of the oxide layer before and after the operation has confirmed that the oxide layer increases the wear resistance by several orders of magnitude. It was also concluded that hard anodic oxidation gives the spindle-neck coating a durability equal to the lifetime of the bearing inserts. We assessed the surface topography by means of microphotography, the yarn kinetic friction coefficient µ k, and the microstructure of the oxide layer before and after the period of operation. This allowed us to find out that the wear of the spindle-neck coating caused by the friction of yarn on the surfaces is determined by the abrasive wear.

Anodizing of A356 T6 Alloys Obtained by Sub-Liquidus Casting

Semi solid processing reduces porosity and amount of trapped gas and it allows heat treatment T6 that improves a hard anodized oxide layer. The aim of this work is to show the anodizing possibility of A356 T6 components conformed by Sub-liquidus Casting (SLC) to improve wear and corrosion resistance. This work compares the anodizing effect on tribological properties and corrosion resistance between components obtained by A6061 T6 extruded alloys and from A356 T6 produced by SLC. The effect of rounded silicon crystals on the coating formation and the fracture produced during the coating growth are described.

The effect of oxide coatings on fatigue properties of 7475-T6 aluminium alloy

The effect of hard anodic oxide and plasma electrolytic oxide coatings on the fatigue strength of 7475-T6 aluminium alloy has been investigated. The coated aluminium alloy was tested using constant load uniaxial tensile fatigue machine. Hard anodising led to an appreciable reduction in the fatigue strength of 7475-T6 alloy of about 75% for a 60 μm thick coating. Further, plasma electrolytic oxidation resulted in reduction of the fatigue strength of about 58% for a 65 μm thick oxide coating. The decrease in fatigue strength of the hard anodic oxide coatings was associated with the stress concentration at the microcracks in the coating. The better fatigue performance of the PEO coatings was attributed to the development of the compressive residual internal stress within the coatings. The reduction in the fatigue strength of the PEO coatings as compared to the uncoated material was associated with the development of the tensile residual internal stress within the substrate. This may cause an early crack initiation in the substrate adjacent to the coating.

A transmission electron microscopy study of hard anodic oxide layers on AlSi(Cu) alloys

Transmission electron microscopy (TEM) has been employed to examine anodic oxide film formation on 99.8 wt.% aluminium, Al–10 wt.%Si and Al–10 wt.%Si–3 wt.%Cu alloys under conditions relevant to hard anodizing. In particular, anodic oxidation of silicon particles proceeded at a significantly reduced rate compared with that of the adjacent aluminium matrix. This gave rise to alumina film encroachment beneath the particles with development of tortuous porosity and, eventually, occlusion of partially anodized particle in the anodic film. Additional effects included the presence of gas-filled cavities above the silicon particles, associated with oxygen generation above the anodizing particle. The presence of such particles and the corresponding gas-filled voids across the anodic film thickness and at the alloy/film interface is considered responsible for the continuous voltage rise during anodizing of the Al–10 wt.%Si alloy, effectively blocking electrolyte access to the pore base and providing local region of high resistance at the alloy/film interface. A direct consequence of the voltage rise was a thickening of the barrier layer at the base of the porous anodic film. For the ternary alloy, with the additional presence of copper and the CuAl2 particles, the latter appear to have undergone complete oxidation, with copper detected in local film regions.

A transmission electron microscopy study of hard anodic oxide layers on AlSi(Cu) alloys

Transmission electron microscopy (TEM) has been employed to examine anodic oxide film formation on 99.8 wt.% aluminium, Al–10 wt.%Si and Al–10 wt.%Si–3 wt.%Cu alloys under conditions relevant to hard anodizing. In particular, anodic oxidation of silicon particles proceeded at a significantly reduced rate compared with that of the adjacent aluminium matrix. This gave rise to alumina film encroachment beneath the particles with development of tortuous porosity and, eventually, occlusion of partially anodized particle in the anodic film. Additional effects included the presence of gas-filled cavities above the silicon particles, associated with oxygen generation above the anodizing particle. The presence of such particles and the corresponding gas-filled voids across the anodic film thickness and at the alloy/film interface is considered responsible for the continuous voltage rise during anodizing of the Al–10 wt.%Si alloy, effectively blocking electrolyte access to the pore base and providing local region of high resistance at the alloy/film interface. A direct consequence of the voltage rise was a thickening of the barrier layer at the base of the porous anodic film. For the ternary alloy, with the additional presence of copper and the CuAl 2 particles, the latter appear to have undergone complete oxidation, with copper detected in local film regions.

パルスＹＡＧレーザー照射によるＡｌ硬質アノード酸化皮膜の局部除去挙動

A laser beam micro surface finishing method attempted to remove hard anodic oxide film formed on aluminum specimens. The hardness of the film increases with increasing applied current density during anodizing and decreasing concentration of SO42− ions. Specimens were irradiated in solutions with a pulsed Nd-YAG laser beam through a convex lens with 60mm focal length to remove anodic oxide film locally. Thin anodic oxide film can be removed without cracks by one pulse of laser irradiation, but thick oxide films need several pulses of irradiation removed without cracks. Thick as grown hard anodic oxide film was removed leaving numerous cracks and the size of the removed area increased with irradiation time. However, dyed thick anodic oxide film was removed layerwise at low irradiation power without cracks, because the dyed oxide film absorbed laser energy. The size of removed area of the dyed film did not change with irradiation time.

Effect of Impregnation of Iodine Complex on Friction of Anodic Oxide of Aluminum

Polyvinyl pyrrolidone-Iodine complex (PVP-I) molecules were impregnated into the anodic oxide of an aluminum disk specimen. It was rubbed against a silicon nitride ball specimen using a ball-on-disk type friction test rig. Over the limited range of parameters studied (load: 0.2-1.0 N, sliding velocity: 0.6 mm/s, and sliding distance: 1-7 m), the coefficient of friction decreased to a value as low as 0.01 from values of 0.3 to 0.7 for the anodic oxide surface. Single-crystal iodine rubbed against silicon nitride showed a coefficient of friction of 0.1. The low coefficient of friction is attributed to the thin PVP-I film on the relatively hard anodic oxide. The mechanism of coefficient of friction reduction is the same as that of a thin soft film on a hard substrate.

622 高Cu含有アルミ合金ピストンリング溝への硬質陽極酸化(OS5 21世紀に挑むエンジン技術)

622 高Cu含有アルミ合金ピストンリング溝への硬質陽極酸化(OS5 21世紀に挑むエンジン技術)

Friction behaviour of anodic oxide film on aluminum impregnated with molybdenum sulfide compounds

In order to improve the lubricity and wear resistance of aluminum anodic oxide films, it is necessary to ensure the film layers are dense to prevent cracking, and to harden the films as well as reduce the shear stress of the film surfaces. From this view point, lubricious, hard anodic oxide films have been studied in the past, but fully satisfactory results have yet to be realized. In this paper, we report on our study of the re-anodizing of anodic oxide film in an aqueous solution of (NH)MoS. Molybdenum sulfide and compounds filled the 20-nm diameter pores of the film, creating internal stress which compressed the film, suppressing the occurrence of cracks and reducing the friction coefficient.