Friction characteristic of micro-arc oxidative Al2O3 coatings sliding against Si3N4 balls in various environments (original) (raw)
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Sigma mühendislik ve fen bilimleri dergisi, 2024
In this study, an alumina (Al 2 O 3) ceramic coating and a composite coating containing titanium dioxide (TiO 2) particles were prepared on surfaces of AA2024 substrates by micro-arc oxidation (MAO) treatment. The effects of micro-sized (≈20-30 µm) TiO 2 particles incorporated into electrolyte on the microstructure, phase and chemical composition, thickness, and friction behavior of the coating were investigated. The surface morphologies of the coatings were analyzed by scanning electron microscopy (SEM). The phase and chemical compositions of the coatings were evaluated by means of X-ray diffraction (XRD) and energy-dispersive X-ray spectrometry (EDS), respectively. The friction coefficient of the coatings was investigated using a pin-on-disc tribometer under condition of dry slip sliding. Moreover, the wear tracks were analyzed by SEM. Addition of TiO 2 particles into the electrolyte resulted in the reduction in number of pores and formation of smaller and more uniform pores in comparison with the Al 2 O 3 ceramic coating. XRD analyses demonstrated that the TiO 2 :Al 2 O 3 composite coating was composed of anatase-TiO 2 and rutile-TiO 2 , as well as pure aluminum, α-Al 2 O 3 and γ-Al 2 O 3 which are the primary phases. The friction tests showed a significant reduction in the friction coefficient of the composite coated samples which contains titanium oxide (TiO 2) particles in comparison with Al 2 O 3 coated and uncoated samples.
Surface and Coatings Technology, 2015
The alumina coatings of 100m thickness were deposited on 6061 T6 Al-alloy through micro arc oxidation (MAO) technique. The phase composition across the coating thickness was evaluated using step-wise grinding followed by X-ray diffraction analysis. The microhardness and elastic modulus were measured through micro and nano indentation techniques respectively on the mounted and polished coating cross-section as a function of distance from substrate-coating interface. The coatings represent typical graded composite of -Al 2 O 3 and -Al 2 O 3 phases and accompanied by a corresponding hardness and modulus gradient across the coating thickness. Tribological performance of MAO coatings was evaluated through pin-on-disc wear test under dry (un-lubricated) conditions. The results obtained suggest that the transition from -Al 2 O 3 rich surface sub-layers to -Al 2 O 3 rich inner sub-layers is gradual. On the basis of above experimental results, the critical interrelationships between the coating phase composition, hardness distribution, modulus distribution and the accompanied sliding wear loss has been established. It was found that the simple rule of mixture explains (ROM) the hardness and modulus distribution as a function of phase gradient across the coating thickness while the inverse rule of mixture (I-ROM) is applicable in the case of sliding wearphase gradient relationship. Further, the relationships established were utilized to evaluate the mechanical and tribological properties of pure -Al 2 O 3 and -Al 2 O 3 phases. The properties of gamma alumina such as hardness, elastic modulus and sliding wear resistance have been reported for the first time in the present work. Further, the worn surface examination indicate that the formation of mechanically mixed layer (MML) which subsequently undergoes abrasive wear and micro-crack induced chipping as the predominant material removal mechanism during dry sliding wear tests.
Kinetics and Properties of Micro Arc Oxidation Coatings Deposited on Commercial Al Alloys
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science - METALL MATER TRANS A, 2007
The micro arc oxidation (MAO) technique is being increasingly recognized as a novel and ecofriendly means of depositing dense ceramic oxide coatings on Al and its alloys. In the present study, the deposition kinetics, surface roughness, morphology, phase distribution and the microhardness of the MAO coatings deposited on ten different commercially available Al substrates having widely differing chemical composition has been investigated. Further, the tribological properties of the coatings obtained on different Al alloys in comparison with the bare substrates have also been evaluated using dry sand abrasion, solid-particle erosion and pin-on-disc dry sliding wear tests. The results clearly demonstrate that the alloying elements added to the Al substrate substantially influence the MAO coating deposition kinetics and coating properties. In the case of Al-Si alloys, the coating deposition kinetics is non-linear and the Al6Si2O13 (mullite) is observed to form. With increasing Si content, the corresponding mullite phase also increases. Increasing mullite content in the coating adversely affects the tribological performance. Excepting Al-Si alloys, all other alloys investigated including commercial purity Al exhibit linear coating deposition kinetics. Of all the alloys investigated, Al-Li alloy exhibits the highest coating deposition rate and the 6061 T6 Al alloy exhibits the best coating properties.
To Investigate Dry Sliding Wear of Micro Arc Oxidated Al 6061
2015
treatment for the production of ceramic oxide coatings with great properties, such as high wear and corrosion resistance, on metal substrates, particularly aluminum and magnesium alloys. In the present investigation dry sliding wear behavior of micro arc oxidated Al 6061 has been investigated to determine weight loss of samples on Pin on Disk set up. Three parameters are selected to investigate the dry sliding wear i.e. Load, Speed and Sliding Distance. The design of experiments (DOE) approach using Taguchi method (L27 Orthogonal Array) was employed to analyze the wear behavior of MAO Al 6061 Alloy. Signal-to-noise ratio, analysis of variance (ANOVA) and regression equation were used to investigate the influence of parameters on the wear rate.
Influence of SiO2 and MnO2 additives on the dry friction and wear performance of Al2O3 ceramic
Materials & Design, 2001
Alumina is widely selected in the design of components for high engineering applications mainly because of its high wear resistance, high compressive strength, low specific density and high temperature capability. Processing and manufacturing of pure alumina products is a difficult and expensive task. Therefore, additional compounds are added to alumina to reach more complex component design, to minimise the product processing and manufacturing costs. In this investigation we studied and explored the influence of additional compounds, speed and load values on the friction and wear behaviour of alumina ceramic. Wear tests for alumina and alumina samples contained w3% SiO and w1.5%MnO , addition compounds was carried out with a pin-on-disc 2 2 machine. Tribological tests were under 2.5, 5 and 10 N loads and at speeds of 0.5 and 1 mrs. The specific wear rates were deduced from mass loss. The wear rate for alumina without additional compounds was in the order of 10 y8 to 10 y7 mm 2 rN. while the wear rate values for alumina with additional compounds were in the order of 10 y6. Moreover, the wear rate showed more sensitivity to the applied load, particularly at low sliding speeds.
Materials and Design, 2009
Influence of oxalic acid addition to sulphuric acid bath on the mechanical properties of the oxide layers formed on aluminium has been examined. For this purpose two Doehlert experimental designs with three variables (temperature, current density, sulphuric acid concentration) and four variables (oxalic acid concentration, temperature, current density, sulphuric acid concentration) were realized. Four responses were studied namely: growth rate (V e ), Vickers microhardness (D), weight loss after abrasion (W a ) and deflection at failure (D f ) of the anodic oxide layer. A comparative study based on surface responses was achieved. Compared with sulphuric acid bath, it was found that the addition of oxalic acid permits high growth rates, high abrasion resistance and high microhardness but less ductile layers. The observed mechanical properties of the oxide layers can be related to their morphology revealed by SEM observations and their chemical composition determined by GDOES.
IRJET-TO INVESTIGATE DRY SLIDING WEAR OF MICRO ARC OXIDATED AL 6061
Micro Arc oxidation (MAO) is a surface treatment for the production of ceramic oxide coatings with great properties, such as high wear and corrosion resistance, on metal substrates, particularly aluminum and magnesium alloys. In the present investigation dry sliding wear behavior of micro arc oxidated Al 6061 has been investigated to determine weight loss of samples on Pin on Disk set up. Three parameters are selected to investigate the dry sliding wear i.e. Load, Speed and Sliding Distance. The design of experiments (DOE) approach using Taguchi method (L27 Orthogonal Array) was employed to analyze the wear behavior of MAO Al 6061 Alloy. Signal-to-noise ratio, analysis of variance (ANOVA) and regression equation were used to investigate the influence of parameters on the wear rate.
Revista de Metalurgia
Two macro-roughness patterns namely spiral grooving and diamond knurling were performed on an AISI/SAE 1045 cylindrical steel bar. Al2O3 + 13 wt.-% TiO2 powder was deposited by utilizing a multi-pass torch. Microstructure, microhardness and wear resistance were analyzed. The presence of both γ-Al2O3 and α-Al2O3 throughout the coating was promoted by partially melted and un-melted particles; however, the formation of interlayers of hard α-Al2O3 was influenced by the re-heating during the multi-pass torch causing transformation from γ-Al2O3→α-Al2O3. Knurling pattern specimens contained less defects owe to a suitable splat accommodation thus strengthening the inter-splat anchorage. The improved sliding wear resistance was influenced by both the combination of γ-Al2O3 (toughness) and α-Al2O3 (hardness) phases and, predominantly by the reduced porosity and micro-cracks in specimens with the knurling pattern.
Tribology Letters, 2004
Commercially available, monolithic alumina ceramic was modified using CO 2 -laser irradiation by surface remelting and adding HfO 2 powder. Scanning electron microscopy revealed that the microstructure of the modified ceramic consisted of a fine lamellar eutectic Al 2 O 3 -HfO 2 phase embedded in the Al 2 O 3 matrix. Differences in the microtribological properties of the matrix and the eutectic phase could be measured by friction force microscopy (FFM) during unlubricated sliding contact with a silicon tip at room temperature as a function of relative humidity of the surrounding air and normal load. The dependence of the friction coefficient and the pull-off force on humidity was explained by the formation of lubricating tribochemical surface layers and described by theoretical models.