(大連理工大學(xué) 材料科學(xué)與工程學(xué)院，大連 116024)
摘 要: 采用熱重(TGA)方法測(cè)定純Ni在800 ℃無應(yīng)力及外加壓應(yīng)力為10和20 MPa時(shí)的氧化動(dòng)力學(xué)曲線，通過掃描電鏡觀察有無壓應(yīng)力作用下的氧化膜表面和截面形貌，分析壓應(yīng)力作用下氧化動(dòng)力學(xué)的變化和氧化膜的失效形式，從金屬空位擴(kuò)散的角度討論壓應(yīng)力對(duì)純Ni高溫氧化行為的影響。結(jié)果表明：純Ni在800 ℃時(shí)氧化，外加壓應(yīng)力增大其氧化速率，這是由于外加壓應(yīng)力對(duì)氧化膜結(jié)構(gòu)的影響造成的；無壓應(yīng)力作用時(shí)，氧化膜為脊?fàn)钛趸铮欢趬簯?yīng)力作用下，氧化膜由粒狀NiO組成，這增大晶界擴(kuò)散的短路擴(kuò)散；且壓應(yīng)力促進(jìn)空位在氧化膜/金屬界面的聚集、粗化，弱化界面，改變氧化膜的失效形式。
關(guān)鍵字: Ni；壓應(yīng)力；擴(kuò)散；高溫氧化；空位
pure nickel at 800 ℃ in airv
（School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, China）
Abstract:The effect of compressive stress on the oxidation behavior of pure nickel was investigated by thermogravimetric analysis (TGA). Compressive samples were subjected to stresses of 10 and 20 MPa and the oxidation behavior was studied at 800 ℃ in air. The surface and cross section morphologies of the oxidized coating were analyzed by SEM. The change of oxidation kinetic and the failure form of the coatings under compressive stress were analyzed. The effect of compressive stress on the oxidation behavior of pure nickel at high temperature was discussed. The results show that the compressive stress increases the oxidation rate, which is attributed to the effect of compressive stress on the oxidized coating microstructure. Compared with the formation of ridge-like oxide, the compressive stress deduces the formation of particles oxide of NiO, which increases the short-circuit paths for diffusion. In addition, the compressive stresses induce vacancies coalescence at oxide-metal interface and cavities development, thus the strength of oxide-metal interface is weakened, and the failure form of the oxidized coating is changed.
Key words: Ni; compressive stress; diffusion; high temperature oxidation; vacancy
