الفهرس 
صفحة العنوانOnly 14 pages are availabe for public view
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Abstract
TC21 with a chemical composition of Ti-6Al-3Mo-1.9Nb-2.2Sn-2.2Zr-1.5Cr is considered a new titanium alloy that is used in aerospace applications as a replacement for the famous Ti-6Al-4V alloy due to its high strength-to-weight ratio, high operating temperature and corrosion resistance. In order to increase wear resistance of this TC21 Ti-alloy, two different thermal treatment techniques were applied on the studied samples. Solution treatment was applied using two step heating at 1000/800 ˚C for 15 min each and then cooled using water quenching or air cooling to see the effect of cooling rate on microstructure as well as mechanical properties. The solution treated samples were divided into two groups; one was tested as solution treated samples without aging. While, the second group was aged at 575 ˚C for 4 hrs. Maximum hardness of 442 HV was observed for the water quenched and aged samples, while minimum hardness of 340 HV was obtained for water quenched samples without aging. The lowest wear rate was reported for water quenched and aged samples. However, the highest wear rate was reported for solution treated and water quenched samples without aging. In addition, a surface treatment was also applied on the samples using plasma and laser techniques. The plasma surface treatment was performed in two different media of N2 and H2 for 2 hrs each. The plasma surface treatment was done at three different temperatures of 300, 400 and 500 oC at a pressure of 800 Torr. The hardness values were decreased with increasing the heating temperature for both N2 and H2. Maximum hardness of 506 HV was obtained for the sample’s plasma treated at 300 oC in a media of N2 due to the formation of titanium nitrides. However, the lowest hardness of 390 HV was obtained for the samples treated at 500 oC with H2. The plasma treated samples in a media of N2 showed relatively lower surface roughness as compared to the samples treated with H2. In addition, laser surface treatment was applied using different laser scanning speeds of 200, 300, 400, 500, 600 and 700 mm/s with 20 W laser power. Hardness values decreased as the laser beam scanning velocities increased over the surface of the samples due to reduction of the interaction time between the laser beam and the specimen surface.
Based on the aforementioned results of the engineering research work, an educational unit (A Novel Surface Treatments) was planned to include it in the course of materials technology for the second year specializing in production technology. The results of the educational research on the effectiveness of the educational unit in the development of concepts and practical skills of the second year students specialize of production technology at the Faculty of Industrial Education and acquire new skills after the application of educational unit.