Effect of the base material condition on the structure and properties of Al2O3 oxide layers

The paper presents a new method for modelling oxide layers for tribology related needs. The most recent world trends in the machine-building sector, in particular with reference to piston machines, are heading towards reducing their lubrication and cooling. Hence, a question arises, what the upper layer of a ceramic material should be like in order to maintain low wear and low frictional resistance. An oxide layer for tribological needs has been formed on an AlMg2 alloy as a result of hard anodizing in SAS electrolyte. This electrolyte enables the control of oxide layer production parameters, which allowed obtaining for the tests an oxide coating with a wide range of changes in porosity and micro-hardness μHV. Anodizing has been carried out by means of the direct-current method, using a stabilized feeder, GPR-25H30D, for a constant electrical charge density of 180 Amin/dm2. A lead plate has been acted as the cathode in the anodizing process. By means of a scanning electron microscope (SEM), the surface morphology and structure, and the chemical composition of the layers have been analyzed

Properties of composite alluminium oxide-graphite layers obtained by an electrolytic method

The paper presents the mechanical properties of composite aluminium oxide-graphite surface layers. The layers were obtained by an electrolytic method, on a EN AW-5251 aluminium alloy substrate, in electrolytes with different graphite concentrations. The layers produced were subjected to tests with use of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results of tests concerning the microstructure, thickness and microhardness of the layers are presented. aluminium-grafit. Warstwy otrzymano metodą elektrolityczną na podłożu stopu aluminium EN AW-5251, w elektrolitach o różnym stężeniu grafitu. Wytworzone warstwy poddano badaniom przy zastosowaniu elektronowej mikroskopii skaningowej (SEM) oraz spektrometrii fotoelektronów (XPS). Przedstawiono wyniki badań mikrostruktury i morfologii powierzchni oraz grubości i mikrotwardości warstw

The finite element method in tribological studies of polymer materials in tribo-pair with oxcide layer

We present an approach to the analysis of mechanisms of the tribological contact of a thin Al2O3 oxide layer formed under hard anodizing conditions on a plate made of the aluminium alloy EN AW-5251. The oxidation of the 50-μm ceramic layer was carried out for 60 min in a three-component electrolyte (SAS), a three-component electrolyte consisting of adipic, sulphuric and oxalic acid, at a temperature of 298.15 K and a current density of 3 A/dm2. A three-dimensional oxide coating model, based on the computer analysis of images from a scanning electron microscope, is proposed. Tribological tests of stresses, strains and dislocations formed in the oxide layer and in the sample material (a block) were conducted. Modified polytetrafluoroethylene (TG15, TGK20/5, TMP12) and polyetheretherketone with carbon fibre and graphite were used as samples for tests in the tribological couple rider-plate of a linear reciprocating friction tester. A tribological couple modelled in the Solid Edge CAD programme was subjected to numerical analyses using the finite element method in the Autodesk Simulation Multiphysics programme under conditions consistent with actual conditions for contact pressures of 0.25, 0.50, and 1.0 MPa

The Effect of Production Parameters of Oxide Layers on Their Nanostructure, Nanomorphology, and Surface Free Energy

Nanotechnology is currently a very promising field of materials science. One of the most recent directions of research in this field is the nanotechnology of the upper layers for applications in engineering kinematic systems. The paper presents the influence of the production parameters of Al2O3 oxide layers on an EN AW-5251 aluminum alloy substrate on the nanostructure, nanomorphology of these layers, and their energy condition. The energy level was determined on the basis of Surface-Free Energy (SFE), determined from wettability (contact) angle measurements using the Owens-Wendt method. Using systematic scanning, the geometric structure of the surface (SGS) was determined for the produced layers. By means of a scanning electron microscope (SEM), the surface morphology and structure, and the chemical composition of the layers (EDS) were analyzed. Computer analysis of the surface nanoporosity was performed by means of the ImageJ 1.50i program. It was noted in the investigations that the oxide layer production parameters induce changes in the surface free energy of the layers. Changes in the nanomorphology of the upper layers were also observed, depending on the anodizing parameters

Analysis of Al2O3 Nanostructure Using Scanning Microscopy

It has been reported that the size and shape of the pores depend on the structure of the base metal, the type of electrolyte, and the conditions of the anodizing process. The paper presents thin Al2O3 oxide layer formed under hard anodizing conditions on a plate made of EN AW-5251 aluminum alloy. The oxidation of the ceramic layer was carried out for 40–80 minutes in a three-component SAS electrolyte (aqueous solution of acids: sulphuric 33ml/l, adipic 67 g/l, and oxalic 30 g/l) at a temperature of 293–313K, and the current density was 200–400 A/m2. Presented images were taken by a scanning microscope. A computer analysis of the binary images of layers showed different shapes of pores. The structure of ceramic Al2O3 layers is one of the main factors determining mechanical properties.The resistance to wear of specimen-oxide coating layer depends on porosity, morphology, and roughness of the ceramic layer surface.A3D oxide coatingmodel, based on the computer analysis of images froma scanning electron microscope (Philips XL 30 ESEM/EDAX), was proposed

Influence of Anodizing Parameters on Surface Morphology and Surface-Free Energy of Al2O3 Layers Produced on EN AW-5251 Alloy

The paper presents the influence of the surface anodizing parameters of the aluminum alloy EN AW-5251 on the physicochemical properties of the oxide layers produced on it. Micrographs of the surface of the oxide layers were taken using a scanning electron microscope (SEM). The chemical composition of cross-sections from the oxide layers was studied using energy dispersive spectroscopy (EDS). The phase structure of the Al2O3 layers was determined by the pattern method using X-ray diffractometry (XRD). The nanomorphology of the oxide layers were analyzed based on microscopic photographs using the ImageJ 1.50i program. The energetic state of the layers was based on the surface-free energy (SFE), calculated from measurements of contact angles using the Owens-Wendt method. The highest surface-free energy value (49.12 mJ/m2) was recorded for the sample produced at 293 K, 3 A/dm2, in 60 min. The lowest surface-free energy value (31.36 mJ/m2) was recorded for the sample produced at 283 K, 1 A/dm2, in 20 min (the only hydrophobic layer). The highest average value nanopore area (2358.7 nm2) was recorded for the sample produced at 303 K, 4 A/dm2, in 45 min. The lowest average value nanopore area (183 nm2) was recorded for the sample produced at 313 K, 1 A/dm2, in 20 min

Thermal Phenomena in the Friction Process of the TG15 - Hard Anodic Coating Couple

The paper presents a one-dimensional model of heat conduction in a couple consisting of a cylinder made of a sliding plastic material, TG15, and a cuboid made of alloy AW 6061 coated with a hard anodic coating, where the couple is heated with the heat generated during friction. TG15 is a composite material based on polytetrafluoroethylene (PTFE) with a 15% graphite filler, used for piston rings in oil-free air-compressors. Measurement of temperature in the friction zone is extremely important for the understanding and analysis of the phenomena occurring therein. It is practically impossible to introduce a temperature sensor in such a place. Therefore, the interaction taking place in such a couple was modelled using numerical methods. In order to simplify and accelerate the calculations, a one-dimensional model and constant thermophysical parameters of the materials participating in friction were adopted. To solve the proposed model, the finite difference method was used (FDM). The resultant system of equations was solved by means of an explicit scheme

An influence of molybdenum disulfide content in electrolyte on tribological properties of anodic oxide coatings

The paper presents an estimation of the usefulness modification of anodic oxide coatings (AHC) on aluminium alloys with molybdenum disulfide (MoS2) for the improvement of the tribological properties of Al2O3 coatings. Anodic oxide coatings were produced through hard anodising on the EN AW-5251 aluminium alloy in a multi-component electrolyte modified with molybdenum disulfide powder with a grain size below 20 micrometers (concentration of MoS2 powder in electrolyte: 0–80 g/l). Tribological tests of modified AHC were conducted in a surface-surface couple in reciprocating motion at the T-17 research stand simulating the conditions of piston/sealing contact of lubricant-free pneumatic servo-motors. The obtained results indicate a significant reduction of the friction coefficient of a sliding couple consisting of a polymer (PEEK/BG material) and an anodic oxide coating, as well as a reduction of wear of the polymer tribopartner as a result of the modification of the oxide coating with MoS2 (especially in the presence 60 g/l of MoS2 powder in electrolyte). The effect of the modification of anodic oxide coatings with molybdenum disulfide is also a significant reduction of the time of wearing-in of the tested couple

Tribological properties of duplex coatings obtained by sealing in succinic acid

The paper presents the tribological properties of duplex coatings obtained on aluminium alloy EN AW-5251 via hard anodising of aluminium in a multi-component electrolyte and subjected to sealing in succinic acid. Tribological tests were conducted in a couple with a PEEK/BG material in a reciprocating motion at a test stand, T-17, simulating the conditions of cylinder/sealing contact of lubricant-free pneumatic servo-motors. The obtained results show a reduction (to 35%) of the friction coefficient of a sliding couple consisting of a polymer (PEEK/BG material) and an oxide coating, as well as a significant reduction of wear of the polymer tribopartner (to 65%), as a result of the modification of the oxide coating by sealing it for 20 minutes in succinic acid at a temperature of 368 K. The presented research shows that the modifying of oxide coatings via sealing may enhance the operational durability of lubricant-free machines

Tribological properties of the AL2O3 layer modified by tungsten disulfide in cooperation with PEEK/BG material

In this article, the authors pay attention to the tribological behaviours of Al2O3 layers modified by tungsten disulfide powder. Oxide layers of Al2O3/WS2 were obtained by using hard anoding treatment in multicomponent electrolyte of sulphuric acid, oxalic acid and phthalic acid with 10, 20 and 30 g/l WS2 addition. PEEG/BG material was the tribological partner for the Al2O3/WS2 ceramics layer in reciprocating motion, under lubricant free friction conditions. Measurements were made with a T17 tribological tester. The results of the friction coefficient for the sliding couple and wear intensity of the PEEK/BG material are presented. The geometrical structures of the layers of Al2O3/WS2 surface before and after tribological interaction were measured using a Talysurf 3D Taylor Hobson profilograph. The obtained results indicate the following: - There is a possibility to improve the tribological properties of Al2O3 layers through the WS2 powder addition to the electrolyte. - Decreasing of the roughness of the counter-specimen after tribological interaction is the result of applied sliding film and also the amount WS2 powder that was put to the electrolyte