This work evaluates the effect of sodium meta-silicate pentahydrate (SMS) and potassium hydroxide concentrations on properties of Al2O3-TiO2 coatings produced through plasma electrolytic oxidation in a solution containing 3 g L−1 potassium titanyl oxalate, (PTO), using a unipolar waveform with constant current density. The surface and cross-section characteristics of PEO coatings including morphology, elemental distribution, and phase composition were evaluated using FESEM, EDS, and XRD techniques. Voltage-time response indicated the concentration of SMS and KOH had a significant effect on the duration of each stage of the PEO process. More cracks and pores were formed at the higher concentrated solutions that resulted in the incorporation of solution components especially Si into the coating inner parts. Ti is distributed throughout the coatings, but it had a dominant distribution in the Si-rich areas. The coating prepared in the electrolyte containing no silicate consisted of non-stoichiometric γ-Al2O3 and/or amorphous Al2O3 phase. Adding silicate into the coating electrolyte resulted in the appearance of α-Al2O3 besides the dominant phase of γ-Al2O3. The corrosion behaviour of the coatings was investigated using the EIS technique. It was found that the coating prepared in the presence of 3 g L−1 SMS and 2 g L−1 KOH, possessed the highest barrier resistance (~10 MΩ cm2), owing to a more compact outer layer, thicker inner layer along with appropriate dielectric property because this layer lacks the Si element. It was discovered that the incorporation of Ti4+ and especially Si4+ in the coating makes the dielectric loss in the coating.
Fe-3Cr-0.5Mo-0.3C and Fe-3Cr-1.4Mn-0.5Mo-0.3C sintered alloys were plasma nitrided under different conditions. Wear tests were carried out on a pin-on-disc machine at 70 N load. It was shown that nitriding decreased the specific wear rate by one order. The SEM observation of worn surfaces, XRD and EDS analyses of wear debris and the amount of wear particles in comparison with the specific wear rate showed that for sintered steel, Similar to wrought steels, the specific wear rate of 10 -8 mm 3 /N·mm could be considered as a dividing line between mild and
Ion implantation has been used as a surface treatment technique on (Fe,Cr)Al-10%vol Al2O3 nanocomposite to enhance its surface properties. The process was carried out at 150 kV with an oxygen dose of 1 × 1018 ions/cm2 at room temperature. Microstructural characterization and phase composition were performed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) of the Al2O3 layer formed on the nanocomposite surface. Mechanical properties measurements including hardness, fracture toughness and coefficient of friction were studied. Nanoindentation tests demonstrated an increase of 50% in the hardness value after ion implantation. Fracture toughness increased to a value of 21.3 ± 0.9 MPa m1/2 after O2 ion implantation. Scratch test results revealed an improvement in tribological behavior of the oxygen implanted surface compared to the un-implanted substrate. Cyclic oxidation tests, at 1100 °C, revealed that oxygen ion implantation slightly improved high temperature oxidation resistance of the nanocomposite.
'%3e%3cg id='e'%3e%3cg id='c' fill='none' stroke='%23fff' stroke-width='2'%3e%3cpath id='b' d='M0 1h26M1 10V5h8v4h8V5h-5M4 9h2m20 0h-5V5h8m0-5v9h8V0m-4 0v9' transform='scale(1.4)'/%3e%3cpath id='a' d='M0 7h9m1 0h9' transform='scale(2.8)'/%3e%3cuse xlink:href='%23a' y='120'/%3e%3cuse xlink:href='%23b' y='145.2'/%3e%3c/g%3e%3cg id='d'%3e%3cuse xlink:href='%23c' x='56'/%3e%3cuse xlink:href='%23c' x='112'/%3e%3cuse xlink:href='%23c' x='168'/%3e%3c/g%3e%3c/g%3e%3cuse xlink:href='%23d' x='168'/%3e%3cuse xlink:href='%23e' x='392'/%3e%3c/g%3e%3cg fill='%23da0000' transform='matrix(45 0 0 45 315 180)'%3e%3cg id='f'%3e%3cpath d='M-.548.836A.912.912 0 0 0 .329-.722 1 1 0 0 1-.548.836'/%3e%3cpath d='M.618.661A.764.764 0 0 0 .422-.74 1 1 0 0 1 .618.661M0 1l-.05-1L0-.787a.31.31 0 0 0 .118.099V-.1l-.04.993zM-.02-.85 0-.831a.144.144 0 0 0 .252-.137A.136.136 0 0 1 0-.925'/%3e%3c/g%3e%3cuse xlink:href='%23f' transform='scale(-1 1)'/%3e%3c/g%3e%3c/svg%3e)
