Effect of Processing Parameters on the Structural and Mechanical Properties of Micro Arc Oxidized Aluminium Alloy

The micro arc oxidation process (MAO) was applied to a 2024 ingot aluminium alloy by an AC MAO equipment using an alkali based electrolyte. The processing parameters of the process were positive and negative voltage pulse durations. Structural and morphological characterization of the coating were made by a scanning electron microscope (SEM), an X-ray diffractometer (XRD), a surface profilometer and a thickness gage operating according to the Eddy current principle. Cross sectional hardness of the coatings was measured, and reciprocating wear and immersion corrosion tests were performed. XRD analysis showed that an oxide layer comprising - and -Al2O3 phases was produced on the surface, whose thickness and surface roughness varied by the processing parameters applied. Wear and corrosion resistance of the original alloy significantly improved upon the MAO process. Variation of hardness, wear and corrosion resistance with respect to the processing parameters was discussed based on the experimental data obtained.

Ultrasonic Guided Wave Testing System for Piping

In the operation of electric power plant, it is necessary to understand the condition of the pipe quantitatively. The purpose is to prevent the accident caused of the wall thinning portion due to erosion or corrosion. The thickness of the pipe is partially measured with the ultrasonic thickness gage now. However, it is difficult to investigate the wall thinning portion in the pipe quantitatively without confirming it beforehand. In this study, for the purpose to identify the location of thinning, we have developed the ultrasonic testing system using the guided wave that was able to investigate partially the wall thinning portion of all aspects of pipe to be inspected at a time. This system propagates guided wave by using an electro-magnetic acoustic transducer. We understand the extensive condition of the pipe by using this system. Therefore, the efficient investigation of the pipe is available. For that reason, it is expected to contribute to the reliability improvement of facilities and the reduction of maintenance and repairs.