کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
822964 1469565 2007 12 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Silver diffusion and high-temperature lubrication mechanisms of YSZ–Ag–Mo based nanocomposite coatings
موضوعات مرتبط
مهندسی و علوم پایه سایر رشته های مهندسی مهندسی (عمومی)
پیش نمایش صفحه اول مقاله
Silver diffusion and high-temperature lubrication mechanisms of YSZ–Ag–Mo based nanocomposite coatings
چکیده انگلیسی

Yttria-stabilized zirconia (YSZ) nanocomposite coatings consisting of silver and molybdenum were produced by a hybrid process of filtered vacuum arc, magnetron sputtering and pulsed laser depositions for tribological investigations at different temperatures. The coatings with 24 at.% Ag and 10 at.% Mo contents showed a friction coefficient of 0.4 or less for all temperatures from 25 to 700 °C. The wear scar surfaces and coating cross-sections were studied using scanning electron, transmission electron, scanning transmission electron and focused ion beam microscopes, which also provided the information on chemical composition distributions of silver and molybdenum along with microstructure features. It was demonstrated that silver diffusion and coalescence on surfaces played an important part in the high-temperature lubrication mechanism of the YSZ–Ag–Mo coatings. Silver was found to be an effective lubricant at temperatures below 500 °C and its coalescence on the surface isolated molybdenum inside coatings from ambient oxygen. Lubricious oxides of molybdenum were formed and lubricated at temperatures above 500 °C when the silver was worn off the contact surface. For silver containment inside the coating at high temperatures, a multilayer architecture was built by inserting a TiN diffusion barrier layer in the composite coatings. Microscopic observations showed that this barrier layer prevented silver exit to the coating surface. At the same time, this enabled a subsequent lateral lubricant supply toward a wear scar location where the diffusion barrier layer was worn through and/or for a next thermal cycle. The multilayer coating maintained a friction coefficient of 0.4 or less for more than 25,000 cycles, while the monolithic coating lasted less than 5000 cycles. In addition, a TiN surface barrier layer with pinholes was deposited on the YSZ–Ag–Mo composite surface to control vertical silver diffusion. With this coating design, the coating wear lifetime was significantly increased beyond 50,000 cycles.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Composites Science and Technology - Volume 67, Issues 3–4, March 2007, Pages 336–347
نویسندگان
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