Corrosion-wear behavior of AA1050/mischmetal oxides surface nanocomposite fabricated by friction stir processing

In this study, the wear and corrosion characteristics of six-pass friction stir processed (FSPed) AA1050/mischmetal oxide nanocomposite (6PPA) was compared to six-pass FSPed sample without powder (6 PA) and annealed base metal (BM). Different wear characteristics, such as weight loss, wear rate and coefficient of friction (COF) were studied. In order to evaluate the corrosion resistance of samples, immersion and cyclic polarization tests were performed. In addition, worn and corroded surfaces were investigated by field emission scanning electron microscopy (FESEM). The result of pin on disk dry sliding wear test revealed that wear resistance improved by employing FSP through finer grain structure (6 PA sample) and by incorporation of mischmetal oxides (MMOs) through lubrication and load-bearing action of particles (6PPA sample). At the constant load of 30 N, COF decreased from 0.9 to 0.85 and 0.75, and weight loss from 7.4 to 5.7 and 4.5 mg/m × 10−3 for the BM, 6 PA, and 6PPA samples, respectively. According to FESEM study of the worn surfaces, the BM and 6 PA samples show an adhesive wear mechanism, however the wear mechanism changed to abrasive for 6PPA sample. Based on immersion test results, corrosion rate of BM reduced from 0.41 to 0.36 and 0.29 mpy for the 6 PA and 6PPA samples, respectively. Moreover, the results of cyclic polarization test and FESEM investigation showed improved pitting resistance of 6PPA sample.