最新色国产精品精品视频,中文字幕日韩一区二区不卡,亚洲有码转帖,夜夜躁日日躁狠狠久久av,中国凸偷窥xxxx自由视频

In order to improve the Nb-1Zr alloys’ oxidation resistance, a series of NiCr coatings with different composite structure were deposited on Nb-1Zr alloys by Plasma enhanced ion plating bellow 300℃. By means of isothermal oxidation, NiCr coatings’ oxidation resistance property was studied in detail. The mechanism of invalidation and oxidation resistance of NiCr coating with different microstructure was revealed. The results showed that a channel for oxygen diffusion could be formed by the micro holes communicating with each other in the single layer NiCr. So the Nb-1Zr matrix near the interface would be oxidized firstly and Nb₂O₅ based oxide powder was generated which gradually was increased along with the oxidation time, causing the breakage of coating. That “through holes” can be significantly reduced by NiCr multilayer composite structure, but the coatings’ failure mode was not changed. By introducing the Cr interlayer, the diffusion of oxygen would easily be absorbed and a dense Cr₂O₃ layer was formed which can discourage the further diffusion of oxygen into the Nb matrix. And also a dense Cr₂O₃ layer could also be formed on the surface of Cr/NiCr multilayer coating by diffusion of Cr. As a result, the Nb-1Zr alloy’s oxidation resistance could be improved. After oxidizing at 600℃ for 500 hours, The weight gain rate of Nb-1Zr alloy with Cr/NiCr multilayer composite coating was only about 0.08 g/m₂.h.