Effect Of Plasma Electrolytic Oxidation Research Articles

Effect of plasma electrolytic oxidation coating on joining metal to plastic

Joining of magnesium alloy to polyethylene without adhesive using a newly developed friction lap welding technology was investigated. The polyethylene and magnesium alloy were hard to be joined together without surface premodification due to the lack of polar groups on polyethylene surfaces. Strong hybrid joints were achieved after the polyethylene was treated by corona discharge, and the magnesium alloy was subjected to plasma electrolytic oxidation treatment. Scanning electron microscope and high resolution transmission electron microscope observations demonstrated that the high joining strength was attributed to the development of both chemical bonds at the interface and micromechanical interlocking.

Influence of plasma electrolytic oxidation on fatigue performance of AZ61 magnesium alloy

The effect of plasma electrolytic oxidation (PEO) on the fatigue of AZ61 magnesium alloy has been investigated under high cycle conditions in air and 3.5% NaCl solution. PEO employed an alkaline pyrophosphate–silicate–fluoride electrolyte, with an offset square waveform, a frequency of 50Hz, and current density of 130mAcm−2. The PEO treatment led to reductions in the fatigue limit by 38% in air and by 56% in 3.5% NaCl solution. The reduction of the fatigue limit is attributed to cracking of the coating, roughness of the alloy/coating interface, corrosion and influences of Al–Mn particles.

Effect of plasma electrolytic oxidation in the solutions containing Ca, P, Si, Na on the properties of titanium

The surface layers were formed on titanium by plasma electrolytic oxidation (PEO) in the solutions which contain various amounts of Na(2)SiO(3)x5H(2)O, Na(3)PO(4) x12H(2)O and Ca(CH(3)COO)(2) xH(2)O. The layers were characterized using a scanning electron microscope (SEM) coupled with an energy dispersive spectrometer (EDS) and an X-ray diffractometer (XRD). The titanium/oxide surface layer interface was analyzed by X-ray photoelectron spectroscopy (XPS). The adhesive strength of the oxide layers was evaluated by the scratch-test. The bioactivity of the surface was determined by soaking in a simulated body fluid (SBF) for 7 and 30 days. The corrosion resistance was determined by electrochemical methods after 13, 181, and 733 h exposure in SBF at a temperature of 37°C. The oxide layers obtained were rough and porous and enriched with Ca, P, Si, and Na and their properties depended on the concentration of the components of the electrolyte. The results of the electrochemical examinations, after a 13 h exposure in SBF, show that the surface modification by PEO improves the corrosion resistance of titanium and it is not degraded after a long-term exposure in SBF. The electrochemical impedance spectroscopy (EIS) results indicate that the surface layers have a complex structure.

In vitro fatigue behavior of surface oxidized Ti35Zr10Nb biomedical alloy

New compositions of titanium alloys with low Young's modulus as well as multiple surface biofunctionalities are under intense research focus for biomedical applications due to the proven ability of titanium for enhancing implant integration. This study presents the effect of plasma electrolytic oxidation coating on the fatigue response of a novel β-Ti35Zr10Nb alloy tested under physiological conditions (Hanks' solution at 37 °C). The electrolytic oxidation was conducted in calcium acetate/calcium glycerophosphate electrolyte that allowed incorporation of Ca and P within the oxide layer with potential benefits for bone apposition. The fatigue results revealed that the presence of oxide layers decreased significantly the fatigue strength of Ti35Zr10Nb alloy relative to uncoated condition. The specific coating morphology featuring interconnected micropores, microcracks, a scalloped coating/substrate interface, as well as the ceramic nature of the oxide layer was identified as the main factors responsible for the lower fatigue performance of the coated titanium alloy.

Effect of Plasma Electrolytic Oxidation coating on the specific strength of open-cell aluminium foams

Plasma Electrolytic Oxidation (PEO) coating treatment is applied to open celled aluminium foams with different structures, aiming to enhance the mechanical performance of the composite material. The mechanical properties of the coated foams produced are assessed experimentally, both in tension and compression. From experimental results, yield stress is found to increase initially with increasing PEO coating thickness, though this trend is not maintained with thicker coatings. This is caused by the transformation of greater quantities of metal to ceramic with thicker coatings (leading to more flaw-sensitive behaviour), and higher defect density in the surface layer (reducing the strength of the coating material). The specific strength of the samples (the yield strength per unit weight for a fixed volume) is shown to initially increase with coating thickness, although, due to the diminishing mechanical benefit and constant weight increase, the effect of substantial coatings is less beneficial. The optimum coating thickness appears to be in the region of 13 μm for the low porosity replicated foams tested in compression, and a value between 18 and 50 μm for the high porosity investment cast foams tested in tension.

A study on the effect of plasma electrolytic oxidation on the stress corrosion cracking behaviour of a wrought AZ61 magnesium alloy and its friction stir weldment

Friction stir weldments of a wrought AZ61 magnesium alloy produced in a robotic friction stir welder under optimised welding conditions were characterised for microstructure, mechanical properties, corrosion and stress corrosion cracking (SCC) behaviour. The effect of surface modification in the form of a plasma electrolytic oxidation (PEO) coating on the corrosion behaviour of the weldment was assessed. The weldment exhibited a joint efficiency of 94%, nevertheless, the weld nugget region was found to have a higher susceptibility to SCC than its parent material counterpart. Even though the PEO coating had provided a good resistance to general and pitting corrosion, it could not completely prevent SCC of this weldment in ASTM D1384 solution.

Effect of plasma electrolytic oxidation coating on the stress corrosion cracking behaviour of wrought AZ61 magnesium alloy

An attempt was made to understand the effect of silicate based plasma electrolytic oxidation (PEO) coating on the stress corrosion cracking (SCC) behaviour of an AZ61 wrought magnesium alloy. The SCC behaviour of untreated and PEO coated specimens was assessed using slow strain rate tensile tests at two different nominal strain rates, viz. 1 × 10 −6 s −1 and 1 × 10 −7 s −1, in ASTM D1384 test solution at ambient conditions. The PEO coating was found to improve the general corrosion resistance to a significant extent; however, the improvement in the resistance to stress corrosion cracking was only marginal.

Stress corrosion cracking behaviour of a surface-modified magnesium alloy

The effect of plasma electrolytic oxidation (PEO) treatment on the stress corrosion cracking (SCC) of a cast magnesium alloy was assessed. Even though the PEO coating has offered improved corrosion resistance, as evidenced in electrochemical tests, its effect in improving the SCC resistance in ASTM D1384 test solution was only marginal. The SCC behaviour of PEO-coated specimens was attributed to the development of microcracks in the coating, leading to cracking of the substrate under slow strain rate test conditions.